Electroactive Polymers for Self-Powered Actuators and Biosensors: Advancing Biomedical Diagnostics Through Energy Harvesting Mechanisms

Abstract

Electroactive polymers (EAPs) have emerged as versatile materials for self-powered actuators and biosensors, revolutionizing biomedical diagnostics and healthcare technologies. These materials harness various energy harvesting mechanisms, including piezoelectricity, triboelectricity, and ionic conductivity, to enable real-time, energy-efficient, and autonomous sensing and actuation without external power sources. This review explores recent advancements in EAP-based self-powered systems, focusing on their applications in biosensing, soft robotics, and biomedical actuation. The integration of nanomaterials, flexible electronics, and wireless communication technologies has significantly enhanced their sensitivity, durability, and multifunctionality, making them ideal for next-generation wearable and implantable medical devices. Additionally, this review discusses key challenges, including material stability, biocompatibility, and optimization strategies for enhanced performance. Future perspectives on the clinical translation of EAP-based actuators and biosensors are also highlighted, emphasizing their potential to transform smart healthcare and bioelectronic applications.

1. Introduction

1.1. Overview of Electroactive Polymers (EAPs)

Electroactive polymers (EAPs) are a class of materials that exhibit reversible changes in shape, size, or mechanical properties when subjected to an electric field. These materials can be broadly categorized into two types: ionic EAPs (which undergo deformation due to ion movement or solvent absorption) and electronic EAPs (which deform due to the application of electric fields leading to charge redistribution within the polymer structure) [1,2]. EAPs have gained significant attention due to their ability to mimic biological systems, offering flexible, lightweight, and highly adaptable properties, making them ideal candidates for use in a wide range of applications, particularly in biomedical and robotic fields. The principal advantage of EAPs lies in their ability to convert electrical energy into mechanical work, often exhibiting high flexibility and stretchability, which traditional materials such as metals or ceramics cannot achieve. EAPs are often compared to biological muscles due to their capacity to respond to electrical stimuli and produce mechanical motion similar to that of biological systems [3]. These polymers can be utilized as actuators to generate mechanical movements and sensors to detect changes in physical stimuli such as pressure, strain, or chemical composition. The application of EAPs in biomedical engineering is particularly appealing due to their biocompatibility, flexibility, and ease of integration with electronic systems. Furthermore, when designed as self-powered systems, these materials can operate autonomously, harvesting energy from environmental sources such as motion or biological fluids, which eliminates the need for external power supplies [4,5]. As such, they present a promising platform for developing advanced medical devices, wearables, and diagnostic tools.

Recent advances in the synthesis and design of EAPs have opened up exciting opportunities in soft robotics, biomedical devices, and sensor technologies [6,7]. These materials are increasingly used in applications requiring lightweight, flexible actuators and sensors that can be integrated into real-time diagnostic systems and wearable electronics for continuous health monitoring.

1.2. Importance of Self-Powered Actuators and Biosensors in Biomedical Diagnostics

The integration of self-powered actuators and biosensors into biomedical diagnostics represents a paradigm shift in healthcare technology. Traditionally, most medical sensors require external power sources for operation, which can limit their efficiency, mobility, and scalability in healthcare applications. However, self-powered systems, especially those using EAPs, are capable of harvesting energy from their surrounding environment, whether through biomechanical motion, body heat, or other physiological energy sources, thereby enabling continuous monitoring without the need for frequent recharging or external energy supplies [8]. Self-powered EAP-based biosensors and actuators offer several key benefits in the context of biomedical diagnostics. First, they enable the real-time, continuous monitoring of critical health parameters such as glucose levels, blood pressure, and biomarkers related to various diseases. For instance, glucose monitoring via sweat-based biosensors can provide patients with constant feedback on their blood glucose levels without the need for invasive testing [9,10]. These systems can also offer improved accuracy and sensitivity, thanks to the high responsiveness of EAPs to small changes in the environment, including mechanical deformations or chemical interactions. Second, EAPs have the unique capability to integrate sensing and actuation into a single device. This dual functionality is particularly useful in applications such as drug delivery systems, where the biosensor can detect a physiological trigger (e.g., a biomarker) and, in response, activate a drug release mechanism [11,12]. In addition to their use in diagnostic systems, EAP actuators have been utilized in prosthetics and soft robotics, where their ability to produce motion with high flexibility and low energy consumption makes them ideal for creating human-like movements and devices that conform to the body’s natural biomechanics [13]. Another major advantage is the ability of these self-powered systems to operate in remote or resource-limited settings. For example, EAP sensors and actuators can be embedded into wearable health monitors or implantable devices that continuously collect and transmit data without requiring manual intervention or maintenance [14].These systems could significantly improve patient outcomes by providing healthcare professionals with up-to-date information, facilitating early disease detection and personalized treatment plans. Furthermore, self-powered biosensors and actuators offer the potential for sustainable healthcare practices. By eliminating the need for batteries or frequent power recharging, the reliance on external energy sources is reduced, which lowers the environmental impact and operational cost of healthcare devices. This is particularly important in the development of wearable technologies for long-term health management, such as chronic disease monitoring and elderly care, where the sustainability of energy sources is crucial [15].

1.3. Scope and Objectives of the Review

Scope:

This review provides a comprehensive exploration of self-powered electroactive polymers (EAPs) in the context of actuators and biosensors for biomedical applications.

The review focuses on the fundamental principles of EAPs, their energy harvesting mechanisms, and their integration into autonomous systems for biomedical diagnostics.

It highlights the role of nanomaterials in enhancing the performance of EAP-based devices, especially in terms of sensitivity, biocompatibility, and power generation.

This review also covers recent advancements in wearable and implantable biosensors, including those that monitor vital signs and detect biomarkers for disease diagnosis.

The integration of flexible electronics, wireless communication, and AI for real-time monitoring is discussed.

Objectives:

To provide an overview of the different types of electroactive polymers used in self-powered actuators and biosensors.

To review the mechanisms of energy harvesting in EAP-based systems, including piezoelectric, triboelectric, and ionic conductivity mechanisms.

To explore the applications of EAP-based actuators and sensors in biomedical diagnostics, focusing on their potential in real-time health monitoring and personalized medicine.

To examine the challenges and limitations in developing self-powered EAP systems, including material durability, stability, and signal optimization.

To discuss future perspectives and innovations in EAP-based biomedical devices, including their clinical translation and integration into smart healthcare systems.

Although the fundamental principles of electroactive polymers (EAPs) have been established for decades, the integration of EAPs into next-generation self-powered actuators and biosensors for biomedical diagnostics is undergoing rapid and transformative advancements. Unlike previous reviews that primarily focused on material properties or standalone functionalities, this manuscript uniquely emphasizes the convergence of energy harvesting mechanisms, real-time sensing capabilities, and autonomous operation within biomedical environments. It critically assesses recent progress in EAP-based systems, with a focus on miniaturization, biocompatibility, and multifunctionality, which are crucial for implantable and wearable healthcare devices. Furthermore, by systematically identifying performance benchmarks, material challenges, and integration strategies, this review provides timely insights for researchers aiming to design efficient, self-powered diagnostic tools tailored to the demands of modern precision medicine.

2. Fundamentals of Electroactive Polymers and Energy Harvesting Mechanisms

2.1. Representative Electroactive Polymers and Their Chemical Structures

Electroactive polymers (EAPs) exhibit unique electrical, mechanical, and chemical properties that make them suitable for actuators, sensors, and energy harvesting systems in biomedical applications. These polymers respond to external stimuli such as electric fields, pH, or temperature by undergoing changes in shape, conductivity, or mechanical properties. The selection of specific polymers depends on their functional groups, redox activity, conductivity, and biocompatibility. This subsection outlines several widely studied EAPs, providing their chemical structures and roles based on references included throughout this review. Polyaniline (PANI) is one of the most extensively used conducting polymers due to its tunable conductivity, environmental stability, and ease of synthesis. Its backbone consists of alternating benzenoid and quinoid units, and it exists in various oxidation states (leucoemeraldine, emeraldine, and pernigraniline), with emeraldine salt being the conductive form. Its conductivity arises from the protonation-induced delocalization of π-electrons along the conjugated chain. Polypyrrole (PPy) is another prominent EAP, valued for its high conductivity, biocompatibility, and mechanical flexibility. Its structure is composed of repeated pyrrole rings linked through carbon–carbon bonds. PPy can undergo electrochemical oxidation, allowing it to expand or contract based on the movement of dopant ions, a mechanism central to its actuator behavior. Poly(3,4-ethylenedioxythiophene) (PEDOT), often used as PEDOT:PSS (blended with polystyrene sulfonate), is a stable, highly conductive polymer with excellent transparency and flexibility. The EDOT monomer forms a thiophene ring fused with an ethylenedioxy group, enhancing its planarity and charge mobility. PEDOT:PSS is widely used in biosensors due to its low impedance and strong adhesion to biological substrates. Polythiophene (PT) and its derivatives are known for their high stability and processability. These polymers consist of thiophene units that form π-conjugated chains, allowing effective charge transport. Substituted versions like poly(3-hexylthiophene) (P3HT) improve solubility and mechanical performance, making them suitable for flexible devices. Polyvinylidene fluoride (PVDF) and its copolymers such as PVDF-TrFE are piezoelectric EAPs. They consist of a linear backbone of CH₂–CF₂ units, with strong dipole moments arising from highly electronegative fluorine atoms. Under mechanical deformation, PVDF can generate electrical signals, making it a prime material for self-powered sensors and energy harvesters.

Polyurethane (PU) and silicone elastomers are commonly used in ionic EAPs as flexible matrices for embedding conductive fillers or ionic liquids. While not inherently conductive, they exhibit high stretchability, biocompatibility, and mechanical resilience, making them useful as host matrices for functional composites. Figure 1 below illustrates the chemical structures of these key electroactive polymers [16]. Including these structures aids in understanding how their molecular architecture relates to their electroactive behaviors and suitability for biomedical integration.

2.2. Definition and Types of Electroactive Polymers (EAPs)

Electroactive polymers (EAPs) such as polypyrrole, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and others are a class of polymers that exhibit a reversible change in their shape, size, or other properties when subjected to an external electrical field or stimulus. They are an essential subset of smart materials that find diverse applications due to their flexibility, stretchability, and ability to transduce electrical energy into mechanical motion or vice versa. EAPs are distinguished from conventional polymers because of their electroactive properties, which enable them to undergo dramatic changes in physical form in response to electrical inputs. These changes can be harnessed for various applications, including soft actuators, sensors, and energy harvesting devices [17]. There are primarily two categories of EAPs: ionic and electronic. The distinction between these two types lies in the mechanism through which they change their physical properties when exposed to an electric field. In ionic EAPs, the motion of ions or solvent molecules within the polymer matrix leads to the material’s deformation. In contrast, electronic EAPs work based on the redistribution of electrical charges, often resulting in large deformations and actuation [2].

Ionic Electroactive Polymers (IEAPs)

Ionic EAPs are characterized by their ability to deform due to the movement of ions within the polymer structure. Ionic polymer–metal composites (IPMCs) consist of an ion-exchange polymer like Nafion coated with thin metal electrodes. When a voltage is applied, cation migration causes bending due to electroosmotic flow. Their low-voltage operation and biocompatibility make them suitable for artificial muscles and biomedical actuators. Polyelectrolyte gels (hydrogels) swell or shrink in response to electric fields due to ion movement and osmotic pressure differences. Made from materials like poly(acrylic acid), they respond to electrical, pH, or ionic stimuli. They are ideal for drug delivery systems and soft tissue mimics. Conducting Polymer Actuators (e.g., Polypyrrole, PANI, and PEDOT) are conducting polymers that undergo reversible redox reactions, driving ion exchange and volume change. They provide tunable mechanical properties and operate under low power. Applications include biosensors, artificial muscles, and neural stimulation. Ionic Liquid Crystal Polymers (LCPs) respond to electric fields with an anisotropic shape or alignment changes, thanks to their ordered structure. Doping with ions enhances their responsiveness and electroactive behavior. They are promising for responsive optical elements and microfluidic devices. These polymers typically operate in aqueous or ionic environments and require the presence of electrolytes to function. One well-known example of an ionic EAP is the ionic polymer–metal composite (IPMC), which consists of a polymer membrane impregnated with an electrolyte and coated with metal electrodes on either side [18]. When an electric field is applied, the cations within the polymer move toward the cathode, causing the polymer to deform, thus acting as a soft actuator. The deformation is highly reversible, making these materials ideal for low-power, flexible actuators [6].

Figure 2, a schematic illustration, highlights the chemical structures of key electroactive polymers widely employed in biomedical applications, including polypyrrole (PPy), polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT), and polyvinylidene fluoride (PVDF). Each polymer demonstrates unique electronic and ionic conductivity, which arises from their conjugated backbones or polar functional groups. For instance, the π-conjugated system in PPy and PEDOT allows for effective electron delocalization, making them excellent candidates for biosensors and neural interfaces. PANI, with its tunable oxidation states, exhibits high environmental stability and conductivity, essential for actuator applications. Meanwhile, PVDF is a ferroelectric polymer known for its piezoelectric properties, making it suitable for energy harvesting and tactile sensors. These molecular architectures critically influence the performance of EAPs in various self-powered and responsive biomedical devices.

Electronic Electroactive Polymers (EEAPs)

Electronic EAPs, on the other hand, operate by applying an external electric field to cause charge redistribution within the polymer. The deformation in electronic EAPs is primarily a result of the electronic response of the polymer material, where external electrical stimulation induces mechanical movement. An example of this category includes dielectric elastomers, which are soft, stretchable materials that expand or contract in response to electric fields. These materials can be utilized for both actuation and sensing purposes, offering a range of biomedical applications in the form of prosthetics, artificial muscles, and flexible sensors [13]. Electroactive polymers have attracted significant attention because of their versatility, biocompatibility, and ability to integrate into soft, flexible structures. They provide unique solutions in biomedical applications where conventional materials, like metals or ceramics, may not be suitable due to their rigidity and bulkiness. Figure 3, depicting electrically stimulated molecular release using electroactive polymers (EAPs), represents a promising approach for controlled drug delivery and therapeutic applications. EAPs respond to electrical stimulation by undergoing conformational changes, ion migration, or redox reactions, which can be harnessed to regulate the release of bioactive molecules [19]. This “on-demand” release mechanism is particularly advantageous for precision medicine, enabling site-specific and temporally controlled drug administration. For example, polypyrrole (PPy)- and polyaniline (PANI)-based EAPs facilitate the electrochemical release of drugs, peptides, or growth factors in response to an external electrical trigger. Such smart systems can be applied in neural interfaces, tissue engineering scaffolds, and implantable drug delivery devices, improving therapeutic efficacy while minimizing systemic side effects. Future advancements in EAP-based molecular release systems may integrate biosensors and closed-loop control mechanisms for autonomous and adaptive drug release tailored to individual patient needs.

2.2.1. Energy Harvesting Mechanisms

Energy harvesting refers to the process of capturing and storing ambient energy from the environment and converting it into usable electrical power. In the context of electroactive polymers, energy harvesting involves converting mechanical energy (such as body movement or vibrations) or environmental energy (like heat or humidity) into electrical energy. This process is central to creating self-powered systems, including biosensors and actuators, that can operate without relying on external power sources [20]. Energy harvesting in EAPs primarily takes advantage of the following mechanisms:

Piezoelectricity: The generation of electric charge in response to mechanical stress or deformation.

Triboelectricity: The generation of electric charge through friction between materials with different electron affinities.

Ionic Conductivity-Based Mechanisms: These mechanisms rely on the movement of ions within the polymer matrix when subjected to an electric field or mechanical stress.

The energy conversion mechanisms employed by electroactive polymers (EAPs) leverage fundamental electromechanical interactions to transform ambient stimuli into electrical signals, which are crucial for developing autonomous biomedical systems [21]. In piezoelectric polymers, such as PVDF or its copolymer PVDF-TrFE, the internal dipole alignment is reoriented under mechanical stress, generating a transient voltage across electrodes, a mechanism particularly effective for low-frequency biomechanical movements like walking or heartbeats. This makes them ideal for integrating into patches or wearable textiles for energy harvesting. In contrast, triboelectric energy conversion is governed by the electrostatic induction that results from the repeated contact and separation of materials with opposing triboelectric polarities; this process accumulates surface charges that can drive currents through an external circuit. Polymer nanocomposites with micro/nano-patterned surfaces have demonstrated enhanced charge density, significantly improving energy output from subtle motions such as skin flexion or finger taps. Ionic conductivity-based conversion, often observed in hydrogels, Nafion-based IPMCs, or ionogels, exploits the migration of mobile ions when exposed to external mechanical or electrical stimuli. These systems are capable of mimicking biological signal pathways and are particularly suitable for interfacing with soft tissues and organs. Unlike purely electronic mechanisms, these ionic systems are inherently softer and hydrated, enabling long-term implantation and bio-interactivity. By combining these mechanisms either in tandem or through hybrid architectures, researchers have created robust self-powered systems capable of both sensing and actuating functions in next-generation healthcare technologies.

2.2.2. Piezoelectricity

Piezoelectricity is the generation of electrical charge in response to mechanical stress or deformation. It occurs when certain materials, including specific polymers, undergo a deformation under applied mechanical forces, resulting in the alignment of dipoles within the material. This alignment leads to an electrical potential difference, which can be harvested for power generation or used for sensing applications [22]. In piezoelectric EAPs, mechanical deformation can be induced through various means, such as body movement, mechanical vibrations, or pressure changes. For example, when an EAP-based piezoelectric material is subjected to compression, tension, or bending, the polymer experiences a change in its internal structure, which induces an electrical charge proportional to the applied force. This makes piezoelectric EAPs highly suitable for energy harvesting from low-frequency mechanical movements, such as those produced by the human body during walking or breathing [23]. Piezoelectric EAPs can be integrated into wearable devices or implantable systems to provide continuous, self-sustained power for sensors and actuators. The ability to harness energy from everyday motions significantly reduces the need for external batteries, which is a critical consideration for long-term, reliable operation in biomedical applications [24]. The high energy conversion efficiency and scalability of piezoelectric systems make them ideal for powering biosensors used for health monitoring and diagnostics.

2.2.3. Triboelectricity

Triboelectricity involves the generation of electrical charge through the contact and separation of two materials with different electron affinities. This phenomenon is widely seen in everyday occurrences, such as when two materials rub together and one becomes positively charged while the other becomes negatively charged. Triboelectric generators (TEGs) can capture this frictional energy and convert it into electrical power, which can be used for various applications, including energy harvesting and sensing [25]. The application of triboelectricity in EAPs enables the design of self-powered devices that can harvest mechanical energy from external vibrations, body motion, or environmental sources like wind or human contact. In the biomedical context, triboelectric EAPs can be employed in wearable health monitors or patches, where the friction between the human body and the environment generates electricity that powers sensors monitoring vital signs [20]. Triboelectric EAPs are particularly advantageous in scenarios where other energy harvesting methods are less effective. Their ability to harvest energy from low-frequency mechanical motions, such as walking or even subtle body movements, provides a new frontier for self-powered biosensors in wearable healthcare devices. These systems not only offer a sustainable power source, but also ensure that the devices remain compact, flexible, and lightweight for continuous monitoring [26].

2.2.4. Ionic Conductivity-Based Mechanism

The ionic conductivity-based mechanism is particularly relevant for ionic EAPs, where deformation and energy harvesting are driven by ion movement within the polymer matrix. In response to an applied electric field or mechanical stress, ions within the polymer (often in an aqueous or electrolyte medium) migrate, causing the material to deform. This movement of ions can be harnessed for energy harvesting purposes or used in sensing applications [27]. One prominent example of an ionic EAP using this mechanism is the ionic polymer–metal composite (IPMC), which consists of a polymer matrix filled with ionic electrolytes. When an external voltage is applied, the ions within the material move towards the electrodes, causing the polymer to bend or contract [28]. This bending motion can be harnessed to produce electrical energy or act as an actuator for medical applications. Similarly, in biosensor systems, ionic EAPs can detect changes in the ionic concentration of bodily fluids, offering real-time monitoring capabilities for health diagnostics [29]. Ionic EAPs are especially useful for biomedical applications due to their soft, biocompatible nature and their ability to respond to low-power stimuli. They can be used to detect subtle changes in the bodily environment, such as the concentration of biomarkers, and offer a promising pathway for developing self-powered diagnostic systems with high sensitivity and flexibility.

2.3. Advantages of Self-Powered Systems in Biomedical Applications

Self-powered systems offer several key advantages in biomedical applications, particularly in the context of continuous health monitoring and diagnostic systems. These advantages include autonomy, sustainability, and convenience, which are critical factors for the development of wearable and implantable devices.

Autonomy and Continuous Operation: Self-powered systems, particularly those based on EAPs, can operate continuously without the need for external power sources or frequent battery replacements. This is particularly important for long-term health monitoring applications, where devices need to function around the clock without interruption or the need for user intervention [30].

Sustainability: By harvesting ambient energy, self-powered EAP-based systems reduce the need for conventional power sources such as batteries, which can be costly, environmentally harmful, and cumbersome to replace [31]. This sustainability makes them highly suitable for applications where power autonomy is a critical requirement.

Biocompatibility and Flexibility: The inherent flexibility and softness of EAPs make them ideal for integration into wearable and implantable systems [32,33]. They conform to the body’s contours, offering a comfortable fit for the user, which is essential for ensuring patient compliance, especially in chronic disease management and elderly care.

Minimization of External Devices: Self-powered systems reduce the reliance on bulky external power supplies, meaning that devices are lighter, smaller, and easier to integrate into daily life. This has significant implications for the development of non-invasive, continuous health monitoring systems [34]. These advantages underscore the transformative potential of self-powered EAP-based devices in revolutionizing personalized medicine and healthcare delivery, ultimately improving patient outcomes through continuous, real-time diagnostics.

Table 1. Comparative overview of electroactive polymers (EAPs), energy harvesting mechanisms, and their advantages in biomedical applications.

Category	Type of EAP	Energy Harvesting Mechanism	Key Advantages for Biomedical Applications	Representative Polymer Structure	Ref.
Electroactive polymers (EAPs)	Ionic EAPs (IPMCs, hydrogels)	Ion movement within the polymer matrix due to applied voltage	- Soft, flexible, and biocompatible - Low-power operation - Suitable for sensing and actuating functions	Nafion (–[CF2–CF(CF3)]– SO3−H+) or hydrogel matrix (e.g., polyacrylamide)	[35]
	Electronic EAPs (dielectric elastomers)	Electrical charge redistribution in response to an electric field	- High actuation strain - Large deformation - Suitable for prosthetics and artificial muscles	PDMS (–[Si(CH3)2–O]–) or VHB acrylic elastomer	[36]
Energy harvesting mechanisms	Piezoelectricity	Generation of electrical charge due to mechanical stress/deformation	- Harvests energy from body motion - Suitable for low-frequency mechanical energy harvesting	PVDF (–[CH2–CF2]–) (β-phase)	[37]
	Triboelectricity	Friction-induced charge generation between two materials with different electron affinities	- Effective for capturing ambient mechanical energy - Can be integrated into wearable systems	PTFE (–[CF2–CF2]–) with Nylon or PDMS pairs	[38]
	Ionic conductivity-based mechanism	Ion migration within the polymer matrix driven by applied voltage or stress	- High sensitivity for ionic concentration detection - Useful for biosensing applications	Poly(3,4-ethylenedioxythiophene):PEDOT or Polypyrrole (PPy)	[39]
Advantages of self-powered systems	Autonomy and continuous operation	No need for external power sources or frequent battery replacements	- Ensures continuous, long-term monitoring of health data - Eliminates dependence on battery replacement	PEDOT:PSS or PANI blends	[40]
	Sustainability	Energy harvesting from ambient sources (body movement and environmental energy)	- Reduces environmental impact - Provides sustainable power for biomedical systems	Ecoflex elastomer with embedded conductive fillers	[41]
	Biocompatibility and flexibility	Soft, stretchable materials that conform to the body’s surface	- Comfortable and non-invasive for the patient - Ideal for implantable and wearable medical devices	Gelatin methacrylate (GelMA), PU	[42]
	Minimization of external devices	Eliminates the need for bulky external power supplies	- Reduces size and weight of medical devices - Ideal for everyday use in continuous monitoring systems	CNT-based PANI/PVDF composite films	[34]

provides a comprehensive comparison of various electroactive polymers (EAPs), their associated energy harvesting mechanisms, and the advantages they offer in biomedical applications. The table highlights the distinct types of EAPs, such as ionic and electronic polymers, and outlines the specific energy harvesting mechanisms piezoelectricity, triboelectricity, and ionic conductivity that enable self-powered operation in biosensing and actuation systems. Piezoelectricity and triboelectricity are particularly effective for capturing mechanical energy from body movements and environmental sources, while ionic conductivity-based mechanisms are highly sensitive to ion concentration, making them ideal for biosensors. The advantages of these self-powered systems are also detailed, emphasizing their ability to provide continuous, sustainable power for long-term, non-invasive monitoring without the need for external power sources. Furthermore, the flexibility, biocompatibility, and adaptability of these EAPs make them suitable for wearable and implantable medical devices, offering a promising solution for next-generation biomedical diagnostics and personalized healthcare. This table encapsulates the versatility and potential of EAPs in revolutionizing healthcare applications through energy harvesting mechanisms.

3. EAP-Based Self-Powered Actuators

Electroactive polymers (EAPs) have emerged as a promising material for the development of self-powered actuators, capable of generating motion and force in response to external stimuli, such as electric fields, mechanical stress, or ionic concentration changes [43]. This section delves into the principles of actuation in EAPs, examining the underlying mechanisms, the role of biomechanical energy harvesting, and the applications in soft robotics, biohybrid systems, and medical devices.

3.1. Principles of Actuation

The primary characteristic that makes EAPs attractive for actuator applications is their ability to convert electrical energy into mechanical work. The actuation mechanism relies on the electroactive behavior of the polymer, where deformation is induced by an applied electrical field [44]. The actuation response varies depending on the type of EAP, such as ionic, dielectric, or electronic polymers. These materials exhibit high deformability and large strains under low electrical fields, making them suitable for soft actuators that mimic biological systems. Figure 4 illustrates the electro-actuation mechanism of a piezoelectric polymer actuator, highlighting its ability to convert electrical energy into mechanical motion [43]. This mechanism is governed by the alignment of molecular dipoles within the polymer structure in response to an applied electric field, resulting in controlled deformation. Piezoelectric polymers, such as polyvinylidene fluoride (PVDF) and its derivatives, are widely used due to their flexibility, lightweight nature, and biocompatibility. Their ability to generate strain under electrical stimulation makes them suitable for applications in artificial muscles, microfluidics, and biomedical devices, where precise and responsive actuation is required. Advances in material engineering, including the development of nanostructured composites, aim to enhance the electromechanical efficiency of these actuators, enabling their integration into next-generation wearable electronics and soft robotics.

3.1.1. Mechanisms of Motion and Force Generation

The mechanisms of motion and force generation in EAPs primarily depend on their material composition and the type of electroactive effect utilized. In ionic EAPs, such as ionic polymer–metal composites (IPMCs), actuation is driven by the migration of ions within the polymer matrix when an electric field is applied. This ion movement leads to local swelling or the shrinking of the polymer, generating bending or stretching motions [35,43]. Conversely, dielectric elastomers (DEAs), which belong to electronic EAPs, generate motion via the electrostatic attraction between charged electrodes, causing the material to expand or contract in response to an electric field. The interplay between material properties, electric field strength, and the mechanical load determines the force generation capability of these actuators, with DEAs often achieving high actuation strains and fast response times [45]. These characteristics make EAP-based actuators ideal for applications requiring soft, adaptive motion, particularly where traditional rigid actuators are insufficient.

3.1.2. Biomechanical Energy Harvesting in Actuators

Biomechanical energy harvesting using EAP-based actuators is an innovative method to generate power from human motion or physiological activities. The energy harvesting mechanism in EAP actuators typically involves the conversion of mechanical energy from sources such as muscle movement, joint motion, or body vibrations into electrical energy. This harvested energy can then be used to power the actuator itself, making it self-sustaining. For instance, piezoelectric EAPs can convert the mechanical stress applied to the material into an electrical signal, which can be stored and used to actuate a device [39]. Such systems are not only energy-efficient, but also serve as a source of continuous power, eliminating the need for external batteries or power supplies in wearable and implantable medical devices [46,47,48]. The integration of energy harvesting with actuators offers the potential for long-term, autonomous function, making these systems ideal for applications in healthcare devices, such as artificial muscles and biohybrid robots.

3.2. Applications in Soft Robotics and Biohybrid Systems

EAP-based actuators play a crucial role in the development of soft robotics and biohybrid systems, offering highly adaptable and flexible solutions for complex, biologically inspired motions. In soft robotics, the ability of EAPs to generate large, compliant deformations makes them ideal for creating robotic structures that can mimic the dexterity and mobility of biological organisms. These robots, which can deform in a way that traditional rigid robots cannot, are used in applications such as minimally invasive surgery, rehabilitation devices, and environmental sensing [49]. The versatility of EAPs allows them to be tailored for specific motions and deformations, enabling the creation of robots with bioinspired locomotion and grasping capabilities. Furthermore, EAP-based actuators are also being explored in biohybrid systems, where they are integrated with living tissues to create hybrid devices that combine biological functions with mechanical actuation [50]. These biohybrids can be used for a variety of applications, including advanced prosthetics, organ regeneration, and even environmental sensing in harsh conditions.

3.3. Role in Medical Devices: Artificial Muscles, Prosthetics, and Rehabilitation

EAP-based self-powered actuators have significant potential in the development of medical devices, particularly in the areas of artificial muscles, prosthetics, and rehabilitation systems. Artificial muscles, which mimic the contraction and extension of natural muscle tissue, can be designed using dielectric elastomers or ionic EAPs to provide highly efficient, lightweight, and flexible solutions for soft robotic prosthetics [51]. These artificial muscles can perform complex movements with high precision, making them ideal for patients requiring prosthetic limbs that can closely mimic natural motion. In prosthetics, the use of EAPs allows for the creation of devices that can provide natural, adaptive movement compared to traditional mechanical prosthetics [52]. EAP actuators can respond to various external stimuli, such as electrical signals from the user’s muscles or nerves, to create intuitive control over the prosthetic device. Furthermore, the self-powered nature of these actuators eliminates the need for external power sources, making prosthetics efficient and reducing the maintenance requirements [53]. Rehabilitation systems, such as exoskeletons or wearable robotic devices, also benefit from the use of EAP-based actuators. These devices can assist with physical therapy and rehabilitation by providing gentle, controlled motion to help patients recover strength and mobility after injury or surgery. By utilizing self-powered actuators, these devices can be easily adapted for long-term use, reducing the burden on healthcare systems while improving patient outcomes [54]. So, EAP-based actuators offer significant advancements in the fields of soft robotics, biohybrid systems, and medical devices. Their ability to generate motion and force efficiently while being adaptable and biocompatible makes them ideal candidates for next-generation healthcare solutions.

Figure 5 illustrates the fundamental polarization mechanism occurring in electroactive polymers (EAPs) when exposed to an external electric field, a principle crucial to their function in artificial muscle-like actuators. In their natural, unstimulated state, the molecular dipoles within EAPs are randomly oriented, resulting in no net polarization. Upon the application of an external electric field, these dipoles align in the direction of the field, leading to macroscopic polarization across the polymer matrix. This realignment of dipoles induces internal electrostatic forces and subsequent strain within the polymer, manifesting as a mechanical deformation such as expansion, contraction, or bending depending on the polymer configuration and electrode placement. This electromechanical transduction process is central to the actuation behavior of electronic EAPs (e.g., dielectric elastomers) and is leveraged in designing artificial muscles that mimic the contractile behavior of biological muscles. The degree of dipole polarization and resultant deformation is influenced by parameters such as the dielectric constant, polymer chain mobility, applied voltage, and electrode geometry. The following figure conceptually captures how molecular-level dipole interactions underlie the macroscopic motion, emphasizing EAPs’ potential for creating soft, lightweight, and biocompatible actuators for biomedical applications such as prosthetics, drug delivery pumps, and microfluidic devices.

Electroactive polymer-based actuators serve as foundational elements in the development of soft robotics and biohybrid systems due to their ability to generate controllable, compliant deformations that mimic natural muscle movements. Their application spans from minimally invasive surgical robots to intelligent prosthetics and responsive rehabilitation devices. For instance, dielectric elastomers can produce strain levels exceeding 100% under relatively low voltages, enabling biologically inspired actuation suitable for wearable exosuits and assistive devices. In contrast, ionic polymer–metal composites (IPMCs) operate under low voltage (<5V) and in wet conditions, making them excellent candidates for biomedical implants such as cardiac pacing elements or smart catheters.

Table 2. Comparative overview of EAP-based self-powered actuators: key features, mechanisms, and biomedical applications.

Actuator Type	Actuation Mechanism	Representative Materials	Typical Strain (%)	Operating Voltage	Response Time	Biomedical Applications	Ref.
Dielectric elastomer (DEAP)	Electrostatic (Coulombic force)	VHB 4910, silicone, and polyacrylate	100–300	1–5 kV	<1 ms	Artificial muscles, cardiac compression sleeves, and soft prosthetics	[55,56]
Ionic polymer–metal composite (IPMC)	Ionic migration (bending)	Nafion and Pt/Au electrodes	5–15	1–5 V	~0.1–1 s	Micropumps, artificial cilia, and smart catheters	[56]
Conductive polymer (CP)	Electrochemical actuation	Polypyrrole (PPy) and Polyaniline (PANI)	2–10	1–2 V	1–10 s	Drug delivery pumps and neural interface actuators	[5]
Carbon nanotube (CNT) yarn actuator	Electrothermal/electrochemical	CNTs with electrolyte-infused matrices	1–10	<2 V	<1 s	Prosthetic fingers and biohybrid muscles	[57]
Graphene-based EAPs	Electrostatic or hybrid	Graphene oxide–elastomer composites	20–100	<500 V	~ms	Wearable exosuits, soft grippers, and implantable biosensors	[58]
Hydrogel ionic EAPs	Osmotic/ionic swelling	Polyacrylamideand alginate-based hydrogels	10–50	1–3 V	0.5–5 s	Artificial muscles, biohybrid robots, and tissue engineering scaffolds	[59]

provides a comparative snapshot of these actuator types, outlining their electrical actuation mechanisms (piezoelectric, dielectric, or ionic), response times, durability, and typical medical applications. This comparative framework facilitates the quick identification of the material–platform combinations best suited for specific biomedical tasks, from high-force limb prosthetics to micro-motion neurorehabilitation interfaces. The table complements the detailed textual discussion by providing quantifiable metrics, while the text elaborates on how such metrics translate to practical, clinical, or research functionalities. Moreover, the emergence of self-powered actuation achieved by integrating energy harvesting mechanisms into these EAP systems further enhances their autonomy, reliability, and miniaturization for next-generation wearable and implantable healthcare solutions.

4. EAP-Based Self-Powered Biosensors

Electroactive polymer (EAP)-based biosensors function through various transduction mechanisms, including piezoresistive, piezoelectric, capacitive, and triboelectric effects, depending on the nature of the polymer and the intended sensing modality. These sensors are capable of detecting a wide range of physiological and environmental stimuli such as pressure, strain, vibration, and biochemical markers. A crucial factor in optimizing sensor performance is understanding how operating conditions, particularly the frequency response, pressure sensitivity, and ambient environmental factors, influence the sensing behavior. The operating frequency significantly impacts the dynamic response of EAP-based sensors. For instance, dielectric elastomer sensors and ionic polymer–metal composite (IPMC) sensors typically exhibit frequency-dependent behaviors due to their inherent viscoelastic and ion transport characteristics. At low frequencies (1–10 Hz), which are ideal for capturing biomechanical movements such as gait, respiration, or pulse monitoring, the sensors demonstrate high deformation and signal fidelity. However, at higher frequencies (>100 Hz), relevant to vibration sensing or acoustic wave detection, the response may attenuate due to limited charge mobility or mechanical damping in the polymer matrix. Hence, sensor design must be optimized based on target application frequency ranges. The pressure sensitivity, defined as the change in the signal per unit of pressure (e.g., ΔV/kPa or ΔR/kPa), is another critical metric. High-performance EAP-based pressure sensors can achieve sensitivities ranging from 0.01 to 10 V/kPa, depending on the type of EAP and any incorporated nanomaterials (e.g., CNTs, AgNWs, or graphene). For example, dielectric elastomer sensors integrated with carbon-based fillers exhibit tunable pressure sensitivities, suitable for applications ranging from soft touch detection in prosthetics to deep-tissue pressure sensing in smart bandages. Sensitivity can also be modulated by the polymer thickness, dielectric constant, and electrode configuration. Environmental conditions such as temperature, humidity, and pH can strongly influence sensor behavior, particularly for ionic and hydrogel-based EAPs. For instance, in ionic EAPs like IPMCs, the moisture content plays a critical role in ion mobility, thus affecting both actuation and sensing reliability. Sensors operating in high-humidity or wet environments (such as in vivo or on-skin applications) must be encapsulated with breathable yet protective layers (e.g., PDMS or PU coatings) to maintain stable performance. Similarly, temperature variations can alter the dielectric constant or polymer stiffness, thereby affecting both the baseline output and sensitivity. By incorporating quantitative performance data (such as frequency bandwidths of 1–100 Hz, pressure detection ranges of 0.1–100 kPa, and a stable output in humidity levels up to 90% RH), EAP-based biosensors are increasingly being tailored for specific biomedical and wearable applications. These include continuous cardiovascular monitoring, tactile sensing in prosthetic limbs, and respiratory rate tracking in soft robotic exosuits. The integration of nanomaterials further enhances the performance metrics, enabling multifunctional, high-resolution, and self-powered biosensing platforms.

4.1. Sensing Mechanisms and Applications

4.1.1. Detection of Physiological Signals and Biomarkers

EAP-based biosensors are highly sensitive to various physiological signals and biomarkers, making them ideal candidates for non-invasive and continuous health monitoring. These sensors utilize the electroactive properties of polymers to transduce biological stimuli into measurable electrical responses [39]. For example, EAPs can detect changes in ionic concentrations or mechanical deformations, both of which are characteristic of physiological processes. When placed in contact with human skin or tissues, they can monitor biomarkers such as glucose, lactate, pH levels, and electrolytes in real time. This detection is accomplished by interfacing the EAP material with a suitable receptor or probe that binds specifically to the target biomarker. The binding interaction results in a change in the electrochemical properties of the EAP material, producing an electrical signal that can be measured and analyzed [19]. Recent developments have focused on improving the specificity and sensitivity of these biosensors by integrating nanomaterials, such as carbon nanotubes or graphene, to enhance the electrical conductivity and biocompatibility of EAPs. These hybrid systems can detect low concentrations of biomarkers in complex biological fluids, such as blood, sweat, and urine, making them useful for diagnosing chronic diseases like diabetes or monitoring metabolic conditions [60,61]. Furthermore, by employing signal amplification strategies, these sensors can be designed to detect multiple biomarkers simultaneously, providing a holistic view of a patient’s health status.

4.1.2. Real-Time Health Monitoring (e.g., Glucose, Lactate, and Sweat Analysis)

Real-time health monitoring is one of the most promising applications for external power sources. The ability to harvest biomechanical energy from movements like walking, muscle contractions, or joint motion provides a continuous supply of power for the sensors, enabling long-term, autonomous health monitoring. For instance, glucose monitoring is particularly important for patients with diabetes, as they need continuous feedback on their blood glucose levels. Traditional glucose testing methods are invasive and require periodic blood draws, but EAP-based biosensors offer a non-invasive alternative by monitoring sweat, interstitial fluid, or even the breath for glucose levels [62]. Similarly, lactate sensors based on EAPs have applications in sports medicine and critical care settings, where monitoring the lactate levels in sweat or blood can help assess metabolic stress and the risk of acidosis [63]. This is particularly relevant for athletes who need real-time feedback on their performance or patients in intensive care units who require close monitoring of metabolic conditions. Moreover, sweat analysis using EAP-based biosensors is gaining significant attention, as it offers a non-invasive and real-time method to monitor various biomarkers, including glucose, lactate, cortisol, and electrolytes [64]. This application is particularly advantageous because sweat is an easily accessible biological fluid, and its analysis can provide valuable insights into a person’s health status, including stress levels, hydration, and metabolic rate. By integrating EAP-based biosensors into wearable devices like smartwatches or patches, patients can track their biomarkers continuously, providing crucial information for personalized treatment plans.

4.2. Integration with Flexible Electronics

4.2.1. Wearable and Implantable Sensors for Continuous Diagnostics

The integration of EAP-based biosensors with flexible electronics has enabled the development of wearable and implantable devices capable of continuous diagnostics. Flexible electronics are lightweight, stretchable, and conformable, making them ideal for integration with soft and deformable EAP materials. This combination facilitates the creation of sensors that can be easily incorporated into wearable devices such as patches, wristbands, or smart clothing, as well as implantable devices that can monitor internal physiological conditions [65]. Wearable devices powered by EAP-based biosensors can monitor a variety of physiological signals such as heart rate, blood oxygen levels, and skin temperature, among others. These devices can be worn throughout daily activities without causing discomfort or hindering movement, allowing for real-time monitoring of health conditions. A recent study published in Nano Energy explores the development of implantable piezoelectric nanogenerators (iPENGs) and triboelectric nanogenerators (iTENGs) for self-powered biomedical devices. These technologies harness mechanical movements from internal organs, such as heartbeat and respiration, to generate electricity autonomously. The review highlights the potential of iPENGs and iTENGs in powering implantable devices, including pacemakers and deep brain stimulators, thereby reducing reliance on traditional battery-powered systems [66]. Moreover, the ability to continuously collect and analyze data enables the early detection of potential health issues, enabling proactive healthcare management. Implantable sensors, on the other hand, offer the potential for the in-depth monitoring of internal biomarkers, such as glucose levels or neurotransmitter concentrations, in individuals with chronic conditions. These sensors can be placed in specific areas, such as under the skin or within the bloodstream, to provide continuous feedback on the patient’s health status [67]. The self-powered nature of EAP-based actuators means that these sensors do not require an external power supply or batteries, making them particularly beneficial for long-term use without the need for regular maintenance or recharging.

Figure 6 illustrates the design and functionality of wearable sweat sensors, which utilize electrochemically active materials to enable the real-time monitoring of biochemical markers in bodily fluids [68]. These sensors are integrated into flexible and skin-conformal platforms, allowing for the continuous and non-invasive detection of essential biomarkers such as electrolytes, glucose, lactate, and cortisol. By leveraging advanced nanomaterials, including conductive polymers, graphene-based composites, and metal oxides, these sensors enhance sensitivity, selectivity, and stability. Their application in personalized healthcare, sports performance monitoring, and early disease diagnosis has gained significant attention, as they provide immediate feedback on physiological status. Future developments should focus on improving sensor longevity, wireless integration with smart devices, and the incorporation of multi-analyte detection capabilities for comprehensive health monitoring.

4.2.2. Non-Invasive Monitoring Technologies

One of the most significant advantages of EAP-based biosensors is their potential for non-invasive health monitoring. Non-invasive sensors offer an excellent alternative to traditional methods that require blood draws, biopsies, or other invasive procedures that can be uncomfortable, time-consuming, and prone to complications. EAP-based sensors can monitor physiological parameters such as glucose, lactate, and pH levels using non-invasive techniques, such as skin-based sweat analysis, breath analysis, or optical sensing. For example, glucose monitoring using sweat or interstitial fluid offers a non-invasive solution for diabetes patients who currently rely on fingerstick tests or continuous glucose monitoring systems that require sensor insertion into the skin. EAP-based sweat sensors can detect glucose and other biomarkers in sweat, providing a continuous, pain-free alternative for managing diabetes [69]. Similarly, lactate monitoring via non-invasive EAP biosensors can be used to track physical exertion and recovery in athletes or patients in critical care settings without the need for invasive blood sampling. These non-invasive monitoring technologies are transforming the way healthcare is delivered, offering patients a comfortable, less intrusive means of managing their health.

4.3. Applications in Point-of-Care Diagnostics and Personalized Medicine

EAP-based self-powered biosensors are also paving the way for advanced point-of-care (POC) diagnostics and personalized medicine. POC diagnostics enable rapid testing and immediate results without the need for specialized laboratory equipment, making them invaluable in both clinical and remote settings [70]. EAP-based biosensors can be integrated into portable, easy-to-use diagnostic tools that allow for the real-time detection of biomarkers, such as glucose, lactate, and other key indicators of health. This capability is especially useful in rural or resource-limited areas where access to centralized healthcare facilities may be limited. The ability to monitor physiological markers in real time also plays a critical role in personalized medicine [71]. By continuously tracking biomarkers and other health indicators, EAP-based biosensors can provide tailored treatment plans for patients. For instance, continuous glucose monitoring systems can adjust insulin delivery in diabetic patients based on real-time glucose readings, optimizing treatment and reducing the risk of complications [72]. Personalized health data collected through wearable or implantable EAP sensors can be used to develop individualized treatment protocols, ensuring that patients receive care that is specifically suited to their unique needs. Moreover, EAP-based biosensors can enable accurate disease diagnosis and progression monitoring. By continuously tracking biomarkers over time, clinicians can better understand disease dynamics, such as how a condition evolves or responds to treatment [73]. This can improve the management of chronic diseases like diabetes, cardiovascular diseases, and neurological disorders, ultimately leading to better patient outcomes and effective interventions. So, the EAP-based self-powered biosensors hold great promise for advancing healthcare by offering non-invasive, continuous, and real-time monitoring of physiological parameters [74]. Their integration with flexible electronics allows for the creation of wearable and implantable devices that can monitor a range of biomarkers, providing valuable insights into an individual’s health status. As these sensors evolve, they will play a key role in the shift toward personalized medicine, enabling proactive and targeted approaches to healthcare management.

Table 3. Comparative overview of EAP-based self-powered biosensors: sensing mechanisms, applications, sensitivity, operating conditions, and limitations.

Application Area	Sensing Mechanism	Target Biomarkers/Function	Sensitivity/Detection Limit	Operating Conditions	Limitations	Ref.
General biosensing	Piezoelectricity, ionic conductivity, and electrochemical response	Converts physiological signals into electrical output	Up to 350 µA/mM·cm2; detection limits ~0.1 µM–10 µM	10 Hz–1 kHz; skin temperature; ambient humidity	Signal drift, limited power, and material degradation	[39]
Biomarker detection	Ion exchange and electrochemical redox reaction	Glucose, lactate, electrolytes, and cortisol	110–320 µA/mM·cm2 (depending on target); LOD ~0.5 µM (lactate)	Sweat-based sensing; normal pH ~5.5–7.0	Selectivity in complex fluids and interference	[20]
Real-time health monitoring	Ionic conduction and piezoelectricity	Continuous analyte sensing (glucose and lactate)	Continuous tracking; dynamic range up to 20 mM	Sweat, ISF, and breath; temperature 32–37 °C	Accuracy affected by motion and sweat variability	[75]
Flexible electronics integration	Mechanical–electrical transduction	Energy harvesting and real-time biosensing	Power density ~3–5 µW/cm2 (TENG-based)	Stretchable, wearable skin patch format	Low energy conversion efficiency	[76]
Wearable and implantable devices	Triboelectricity and EAP deformation	Smart patches, skin electronics, and glucose sensors	Specificity > 95%, sensitivity varies by fluid	Implanted under skin or adhered on epidermis	Biocompatibility, encapsulation, and long-term stability	[77]
Non-invasive monitoring	Breath, sweat, and ISF sampling with EAP films	pH, Na+, K+, and glucose	Electrochemical sensors: ~120 µA/mM·cm2; LOD < 1 µM	Temperature-dependent; humidity-sensitive	Requires calibration, environmental interferences	[78]
Point-of-care (PoC) diagnostics	Self-powered electrochemical sensing	Infection markers, glucose, and inflammation	Rapid response (<5 min); LOD ~1–10 µM	No external power; portable conditions	Data variability and limited analyte coverage	[79]
Personalized medicine	Continuous real-time feedback loop	Patient-specific biomarker trends	Depends on algorithm and biosensor combo	Wearable/implantable platforms	Privacy, algorithm bias, and power management	[80]

offers a detailed comparative analysis of EAP-based self-powered biosensors, emphasizing their diverse sensing mechanisms, application domains, sensitivity benchmarks, operational conditions, and associated limitations [75,76,77,78,79,80]. These biosensors operate through advanced transduction mechanisms such as piezoelectricity, ionic conductivity, and electrochemical interactions, which convert physiological and biochemical stimuli into quantifiable electrical outputs. This enables the real-time and continuous monitoring of vital biomarkers like glucose, lactate, cortisol, and electrolytes [81,82]. Many of these sensors demonstrate high sensitivity, with detection limits reaching the micromolar or even sub-micromolar range, and maintain operational performance under skin-relevant frequencies and environmental conditions. Importantly, the integration of EAP-based biosensors into flexible and stretchable electronics allows for their seamless deployment in wearable and implantable platforms. These platforms not only provide comfort and conformability, but also facilitate energy autonomy through biomechanical energy harvesting, such as via triboelectric or piezoelectric effects, removing reliance on external power supplies [83]. Their non-invasive sampling capabilities—through sweat, interstitial fluid, or breath—greatly enhance user compliance while minimizing infection risk or discomfort compared to traditional invasive diagnostic procedures [84]. Furthermore, the utility of these sensors extends to point-of-care (PoC) diagnostic tools that deliver rapid, on-site detection without the need for centralized laboratory infrastructure. This makes them particularly valuable in resource-constrained environments. Additionally, the continuous and personalized data obtained through these devices support individualized treatment plans, aligning with modern approaches in precision medicine [85,86]. Despite some limitations—such as environmental sensitivity, power generation constraints, and the need for material stability—EAP-based biosensors represent a transformative shift in biomedical diagnostics by offering accurate, self-powered, and patient-friendly solutions for health monitoring and disease management.

4.4. Quantitative Performance of EAP-Based Biosensors: Sensitivity, Specificity, and Detection Limits

The performance of EAP-based biosensors is significantly defined by key parameters such as sensitivity, specificity, and detection limits, which determine their suitability for practical biomedical applications. For instance, polyaniline (PANI)-based EAP biosensors functionalized with glucose oxidase have demonstrated remarkable sensitivity (~67.8 μA mM⁻¹ cm⁻²) and low detection limits (~5 μM) for glucose detection under physiological conditions, enabling their use in continuous glucose monitoring for diabetic patients [87]. Similarly, CNT-integrated EAP sensors used for lactate detection exhibited high specificity with minimal cross-reactivity to interferents like uric acid and ascorbic acid, and reported detection limits as low as 10 μM [88]. These biosensors are capable of operating within narrow frequency ranges (typically <1 kHz) and under mild mechanical stimuli (pressure range: 0.1–10 kPa), which is ideal for detecting subtle physiological signals such as pulse waves or sweat metabolite variations. Moreover, the specificity of these sensors is enhanced by surface functionalization techniques, including molecular imprinting and enzyme immobilization, which allow for the selective binding of target analytes. For example, EAP-based cortisol sensors have achieved sensitivities of 8.2 nA/nM with detection limits in the sub-nanomolar range (~0.5 nM), proving effective for stress-related hormonal monitoring. Such quantitative insights are critical for assessing biosensor reliability in real-world applications, particularly in wearable and implantable platforms where consistent performance under dynamic environmental and physiological conditions is paramount.

5. Nanomaterial Integration for Enhanced EAP Performance

The integration of nanomaterials into electroactive polymers (EAPs) has shown significant potential in enhancing the mechanical, electrical, and sensing properties of these materials. Nanocomposites and nanostructured EAPs offer remarkable advancements in terms of flexibility, sensitivity, and performance, making them ideal candidates for applications in self-powered actuators and biosensors. The use of nanomaterials improves the efficiency of energy harvesting mechanisms and optimizes the response of EAPs in various biomedical applications.

5.1. Nanocomposites and Nanostructured EAPs

The incorporation of nanomaterials into EAPs results in the formation of nanocomposites, which combine the beneficial properties of both the electroactive polymer matrix and the added nanofillers. These nanocomposites enhance the conductivity, mechanical properties, and responsiveness of the polymer, which are essential for improving the performance of both actuators and biosensors. Nanostructured EAPs, composed of materials with a nanoscale architecture, enable the creation of highly responsive and efficient systems capable of harvesting and utilizing small amounts of biomechanical energy. The following sections discuss some key types of nanomaterials used in EAP integration.

5.1.1. Carbon Nanotubes (CNTs), Graphene, and 2D Materials

Carbon nanotubes (CNTs) and graphene are among the most commonly used nanomaterials for enhancing the performance of EAPs. These materials possess exceptional electrical conductivity, mechanical strength, and flexibility, making them ideal for integration with EAPs to improve actuation and sensing capabilities [89,90]. The incorporation of CNTs into EAPs allows for enhanced piezoelectric and triboelectric properties, which are crucial for energy harvesting and sensor sensitivity. CNTs also contribute to improving the mechanical durability and strength of the polymer, which is vital for long-term use in biomedical applications such as wearable devices and implantable sensors [91]. Graphene, a single layer of carbon atoms arranged in a hexagonal lattice, also exhibits remarkable properties, including high electrical conductivity, high surface area, and excellent mechanical properties. The integration of graphene into EAPs not only improves their conductivity, but also enhances the overall performance of sensors and actuators. Graphene-based EAPs have been shown to exhibit higher flexibility, faster response times, and improved stability in harsh environments, making them ideal for wearable sensors and flexible electronics [92]. Furthermore, two-dimensional (2D) materials such as molybdenum disulfide (MoS2) and transition metal dichalcogenides (TMDs) are gaining attention due to their unique electrical, mechanical, and thermal properties, further contributing to the development of high-performance nanostructured EAPs for advanced biomedical applications [88].

5.1.2. Metal Nanoparticles and Conductive Polymers

In addition to carbon nanomaterials like CNTs and graphene, metal nanoparticles (MNPs), notably gold (Au), silver (Ag), and copper (Cu), have garnered significant attention as functional additives in electroactive polymer (EAP) systems, owing to their superior electrical conductivity, plasmonic activity, and biocompatibility. These metals offer unique electronic and surface characteristics that synergistically interact with polymer matrices, improving not only the electrical, but also mechanical and electrochemical performance. Their high surface-area-to-volume ratio allows for efficient charge transport, making them ideal for enhancing the actuation and sensing functionalities of EAPs in biomedical settings. Gold nanoparticles (AuNPs) are among the most widely employed due to their outstanding chemical stability, non-toxicity, and ease of functionalization with biomolecules. When integrated with polymers like polypyrrole (PPy) or poly(vinylidene fluoride) (PVDF), AuNPs provide localized conduction pathways, reduce charge transfer resistance, and facilitate stronger electrostatic interactions. In biosensing applications, AuNP-doped EAPs have shown enhanced sensitivity and selectivity for glucose, lactate, dopamine, and other critical biomarkers by increasing the available active surface area and promoting faster electron transfer at the interface. The biocompatibility of AuNPs further supports their use in implantable or wearable EAP-based biosensors [87]. Silver nanoparticles (AgNPs) also serve as effective additives in EAPs, particularly for their superior electrical conductivity and strong antimicrobial properties. When combined with conductive polymers like polyaniline (PANI), AgNPs enhance the polymer’s charge mobility, reduce impedance, and contribute to improved actuation efficiency [93]. AgNP-incorporated EAP systems are especially promising in applications such as wound-healing patches or biomedical actuators, where both electrical performance and sterility are essential. Moreover, the plasmonic features of AgNPs allow for optical biosensing applications, such as surface-enhanced Raman scattering (SERS)-based EAP sensors, enabling the label-free detection of disease biomarkers [16,93]. Copper nanoparticles (CuNPs), while less noble than Au and Ag, offer a cost-effective alternative for conductivity enhancement in EAPs. CuNPs display good electrical conductivity and electrochemical reactivity, but require surface passivation or stabilization (e.g., with graphene oxide or polymer coatings) to prevent rapid oxidation [94]. Their inclusion in polymer matrices like PVDF or poly(3,4-ethylenedioxythiophene) (PEDOT) has been shown to improve electromechanical response, actuation force, and stability. Cu-based EAPs are under exploration for use in flexible electrodes, stretchable electronics, and low-cost disposable biosensors, especially for resource-limited settings [16,87]. Overall, the integration of metal nanoparticles into EAP matrices enables the design of hybrid nanocomposite systems with improved electrical conductivity, electrochemical performance, mechanical resilience, and biocompatibility. These enhancements are particularly critical for biomedical applications such as real-time health monitoring, bio-actuated drug delivery, soft robotics, and responsive implants. The rational design and surface engineering of these nanoparticles will continue to play a pivotal role in the future development of high-performance EAP-based technologies.

5.2. Enhancing Sensitivity, Durability, and Biocompatibility

The incorporation of nanomaterials into EAPs significantly improves the sensitivity, durability, and biocompatibility of these systems. Sensitivity is enhanced due to the increased surface area and improved conductivity provided by nanomaterials such as CNTs, graphene, and metal nanoparticles. This allows for the efficient detection of low-concentration biomarkers or small mechanical deformations, which is essential for applications like glucose monitoring, pressure sensing, and muscle motion detection. Furthermore, the enhanced mechanical properties of nanocomposite EAPs result in improved durability, enabling these devices to withstand repeated mechanical deformation or environmental stress without degradation [16,95]. In addition to improving sensitivity and durability, the biocompatibility of nanocomposite EAPs is crucial for their successful integration into biomedical applications. The biocompatibility of nanomaterials such as CNTs, graphene, and metal nanoparticles is a critical factor for ensuring that these sensors and actuators can be safely used in vivo or in wearable applications that come into contact with the skin. Recent studies have demonstrated that the use of biocompatible nanomaterials in EAPs can reduce the risk of inflammatory responses or toxicity, making them suitable for long-term implantation or use in healthcare applications [96]. The combination of enhanced sensitivity, durability, and biocompatibility ensures that nanostructured EAPs can provide reliable, safe, and efficient performance in clinical settings.

Figure 7 illustrates the multifaceted biological responses induced by electroactive polymer–metal composites (EAPMCs) under electrical stimulation, highlighting interactions at both the molecular and cellular levels. Upon electrical activation, EAPMCs modulate the local microenvironment by generating electric fields that influence ion channel activity, particularly calcium and potassium flux, leading to downstream signaling cascades such as MAPK, PI3K/Akt, and Wnt/β-catenin pathways. These signals regulate the gene expression related to cell proliferation, differentiation, and extracellular matrix (ECM) production. At the cellular level, electrical stimulation promotes alignment, migration, and the enhanced viability of various cell types, including fibroblasts, myoblasts, and stem cells. The conductive nature of the polymer–metal matrix facilitates efficient charge distribution, while the polymeric component ensures mechanical compliance with soft tissues. Overall, the figure emphasizes how the integration of conductive composites with bioelectrical cues can guide tissue regeneration and functional recovery, making EAPMCs vital tools in the development of smart, responsive biomedical interfaces.

5.3. Role of Nanomaterials in Energy Harvesting Efficiency

Nanomaterials play a transformative role in enhancing the energy harvesting efficiency of electroactive polymers (EAPs), particularly in self-powered biosensors and implantable healthcare systems. Their integration into EAP matrices addresses several limitations of traditional polymers by significantly improving the mechanical–electrical transduction properties, such as piezoelectric, triboelectric, and electrochemical energy conversion, all of which are critical for continuous operation in autonomous biomedical devices. For instance, carbon nanotube (CNT)-based EAPs have shown exceptional potential in biosensing applications due to their high aspect ratio, excellent mechanical resilience, and ability to generate charge under mechanical deformation. When subjected to physiological movements such as arterial pulsation, breathing, or joint flexion, CNT-integrated piezoelectric systems demonstrate enhanced output voltage and current, enabling them to operate as self-powered sensors for detecting motion-related biometrics such as heart rate, respiration, or muscular activity [97]. Their anisotropic conductivity also facilitates signal selectivity and reduces noise, which is crucial for accurate real-time biosignal monitoring. Similarly, graphene-based nanocomposites offer multifunctionality due to their ultrahigh carrier mobility, tunable surface chemistry, and exceptional triboelectric performance. When embedded in triboelectric nanogenerators (TENGs), graphene and its derivatives enhance the charge transfer and surface charge retention, resulting in higher energy outputs from even minimal biomechanical inputs like skin deformation or tissue vibration. This improvement is particularly beneficial for implantable biosensors, where limited motion is available and efficient energy conversion is vital. Moreover, graphene’s biocompatibility and flexibility make it ideal for conformal contact with tissues, enhancing sensitivity without compromising safety [98]. A recent development in this field involves hybrid nanocomposite EAPs combining CNTs or graphene with metal nanoparticles (e.g., AuNPs or AgNPs) to produce multifunctional self-powered biosensors. These hybrid systems can simultaneously harvest energy and detect biochemical signals, such as glucose, lactate, or urea levels, by integrating piezoelectric sensing with electrochemical detection. For example, a CNT/AgNP-doped PVDF nanocomposite was demonstrated as a wearable TENG that not only harvested motion energy, but also detected sweat metabolites in real time, effectively functioning as a dual-mode health monitoring system.

Moreover, recent advances in implantable piezoelectric generators, such as flexible PVDF-based nanogenerators embedded with aligned CNTs or barium titanate nanoparticles, have enabled energy harvesting from subtle internal movements like heartbeats or diaphragm motion. These generators can continuously power biosensors for days or weeks without an external power input, making them promising candidates for long-term implants that monitor parameters such as pH, ion concentrations, or even early disease biomarkers without requiring battery replacements. In essence, the synergistic integration of nanomaterials into EAPs elevates their energy harvesting capacity, responsiveness, and functional stability. This is critical for the realization of autonomous, wearable, or implantable biosensing systems, where both energy efficiency and material biocompatibility are paramount. As such, nanostructured EAPs are shaping the future of self-powered, intelligent healthcare platforms, capable of real-time diagnostics, personalized therapy, and continuous physiological monitoring in both in vivo and wearable formats [97,98].

In

Table 4. Comparative summary of nanomaterial integration in electroactive polymers for enhanced performance.

Topic	Nanocomposites and Nanostructured EAPs	Carbon Nanotubes (CNTs), Graphene, and 2D Materials	Metal Nanoparticles and Conductive Polymers	Enhancing Sensitivity, Durability, and Biocompatibility	Role of Nanomaterials in Energy Harvesting Efficiency	Ref.
Key nanomaterials involved	Nanofillers (e.g., CNTs, graphene, and metal nanoparticles) integrated into electroactive polymer matrices	Carbon nanotubes (CNTs), graphene, and 2D materials (MoS2, TMDs)	Metal nanoparticles (Au, Ag, and Cu) and conductive polymers (PPy, PANI)	Nanomaterials (e.g., CNTs and graphene) enhance sensitivity, durability, and biocompatibility	CNTs, graphene, and metal nanoparticles enhance piezoelectric and triboelectric properties	[99]
Mechanical properties	Improved flexibility and mechanical strength	Exceptional mechanical strength, flexibility, and tensile properties	Enhanced mechanical properties and flexibility of EAPs	Improved mechanical durability under repeated deformation	Enhanced mechanical performance with improved energy harvesting ability	[31]
Electrical conductivity	Improved electrical conductivity and charge distribution	High conductivity, ideal for piezoelectric and triboelectric properties	Improved conductivity through nanostructured fillers	Enhanced electrical properties increase sensor and actuator performance	Increased conductivity improves energy conversion efficiency	[100]
Biocompatibility	Potential biocompatibility issues with certain fillers	Graphene and CNTs demonstrate good biocompatibility for biomedical use	Biocompatibility of gold nanoparticles and conductive polymers is well established	Reduced inflammatory responses, suitable for implantable devices	Biocompatibility ensures safe use in wearable and implantable applications	[101]
Application areas	Used for soft robotics, biohybrids, and smart biomedical devices	Used in sensors, actuators, wearable electronics, and biohybrid systems	Applied in glucose sensors, biosensors, and implantable electronics	Ideal for long-term health monitoring devices and non-invasive biosensors	Used in self-powered actuators and biosensors for continuous monitoring	[102]
Performance improvements	Enhanced actuation and sensor performance due to improved properties	High piezoelectric and triboelectric properties for energy harvesting	Increased sensitivity and response times for biosensing applications	Enhanced long-term durability, with superior sensor performance	Improved energy harvesting efficiency leads to longer operational times	[103]
Challenges	Dispersion and alignment of nanomaterials and stability issues	Potential cytotoxicity of CNTs and graphene and scalability issues	Conductive polymers may degrade over time and metal nanoparticle leaching	Ensuring long-term stability and biocompatibility in vivo	Ensuring efficiency over long-term use and under dynamic biomechanical conditions	[104]

, a comprehensive overview is provided of how various nanomaterials, including carbon nanotubes (CNTs), graphene, 2D materials, metal nanoparticles, and conductive polymers, contribute to the enhancement of electroactive polymers (EAPs) used for self-powered actuators and biosensors. The table emphasizes the significant improvements in mechanical strength, electrical conductivity, and actuation efficiency that result from the incorporation of these nanomaterials. Notably, materials like CNTs and graphene offer outstanding mechanical flexibility and high conductivity, making them ideal candidates for use in flexible, high-performance EAP-based devices. Furthermore, metal nanoparticles and conductive polymers enhance the biosensing capabilities of EAPs, particularly in applications such as glucose and lactate sensors. The integration of nanomaterials not only improves performance, but also addresses challenges related to biocompatibility and stability, ensuring the long-term efficacy of these devices in medical applications. However, despite these advancements, challenges remain, including issues with the scalability of nanomaterial integration, long-term stability in physiological environments, and potential cytotoxicity. As the field progresses, ongoing research into optimizing nanomaterial dispersion, enhancing biocompatibility, and improving energy harvesting efficiency will continue to drive the development of next-generation self-powered actuators and biosensors for biomedical applications.

6. Challenges and Limitations in EAP-Based Systems

Electroactive polymers (EAPs) have emerged as promising materials for self-powered actuators and biosensors, particularly in biomedical applications. However, despite their advantages, several challenges and limitations hinder the full realization of their potential. These challenges primarily involve material durability, energy generation and storage efficiency, signal optimization, and scalability in manufacturing.

6.1. Material Durability and Stability

Long-Term Performance and Biocompatibility Concerns

One of the primary challenges in the development of EAP-based systems is ensuring their long-term performance and biocompatibility. As EAPs are frequently used in environments that involve continuous mechanical stress and physiological conditions, they must maintain stable mechanical properties, electrical conductivity, and bioactivity over extended periods of time [19]. The polymer matrices that form the basis for most EAPs may degrade due to repeated stress, exposure to moisture, or other environmental factors, leading to a decrease in actuator efficiency or sensor sensitivity. Furthermore, the integration of nanomaterials such as carbon nanotubes (CNTs) and graphene can introduce toxicity concerns, which may affect biocompatibility when used in medical applications. In order to ensure the safety and effectiveness of EAP-based devices, future research must focus on the development of stable, durable, and biocompatible materials [16,105]. Surface modifications and the use of protective coatings can also play a crucial role in improving the longevity and safety of EAPs in biological systems.

6.2. Power Generation and Storage Efficiency

Optimizing Energy Harvesting Mechanisms for Continuous Operation

Another significant challenge is optimizing the energy harvesting capabilities of EAP-based systems to ensure continuous, reliable operation. While EAPs can harvest biomechanical energy through mechanisms like piezoelectricity, triboelectricity, and ionic conductivity, the energy generated is often limited in terms of both output and efficiency. Energy harvesting systems must be able to provide a sufficient and consistent power supply to the actuators and biosensors without relying on external power sources. Additionally, integrating efficient energy storage systems is critical for the functionality of self-powered devices, especially in applications where power needs to be stored for use during periods of low mechanical input, such as during sleep or inactivity. Recent advances in energy storage technologies, including supercapacitors and flexible batteries, show promise in enhancing the overall power management of EAP systems [106,107,108]. However, overcoming the limitations of energy storage, such as capacity, charge/discharge cycles, and flexibility, remains a key challenge for the widespread application of self-powered EAPs in practical biomedical devices.

The generation of reliable and sustainable power is crucial for the autonomous operation of biomedical sensors and devices, especially in resource-constrained or implantable settings. In real-world applications such as continuous glucose monitoring, cardiac rhythm detection, or wearable motion tracking, devices must operate uninterruptedly, often without frequent maintenance or battery replacement. This becomes particularly vital in implantable systems, where replacing power sources can require invasive procedures. For instance, in wearable biosensors integrated into smart textiles or skin-mounted patches, the intermittent biomechanical energy from human movement can be effectively harvested using piezoelectric or triboelectric mechanisms. However, without efficient energy conversion and storage, such harvested power may not meet the demands of continuous data acquisition and wireless signal transmission. As discussed in recent studies [106,107,108], integrating flexible supercapacitors with high energy density into EAP-based systems significantly enhances the energy autonomy of biosensors, enabling their function even during periods of inactivity or low user mobility. For biomedical sensors, especially those designed for long-term health monitoring or therapeutic applications, several critical requirements must be met. These include high sensitivity and specificity to physiological signals, biocompatibility, mechanical compliance, and robust signal stability under dynamic conditions. Additionally, sensors must be operable under varying environmental conditions, such as fluctuations in skin temperature, humidity, and body motion. Taking an example from recent flexible pressure sensors used for arterial pulse monitoring, power must be generated consistently from minor wrist or neck movements, demanding both high sensitivity at low pressure ranges (~0.1–5 kPa) and seamless integration with energy harvesting modules. Moreover, storage units like micro-supercapacitors must exhibit rapid charge–discharge cycles with minimal degradation to support real-time feedback or alerts. Figure 8 illustrates a visionary framework for self-powered wearable and implantable medical devices (WIMDs), eliminating the dependence on traditional battery replacements. The proposed system integrates various energy harvesting technologies, including triboelectric (TENG), piezoelectric (PENG), electromagnetic (EMEH), thermoelectric (TEG), and photovoltaic (PV) harvesters, alongside wireless energy transfer and efficient storage solutions [109]. These energy sources work in synergy with power management, data acquisition, and communication modules, ensuring the continuous and reliable operation of medical implants such as neural stimulators, cardiac pacemakers, and biosensors.

The development of such energy-autonomous systems holds immense potential for enhancing patient safety, reducing surgical interventions for battery replacement, and enabling long-term healthcare monitoring. Future advancements will focus on optimizing energy efficiency, miniaturization, and integration with AI-driven diagnostics for next-generation biomedical applications.

6.3. Signal Optimization and Noise Reduction

Improving the Sensitivity and Selectivity of Sensors

EAP-based biosensors face challenges in terms of signal optimization and noise reduction, which are critical for ensuring accurate and reliable readings in real-time health monitoring. The high sensitivity of EAP-based sensors is advantageous for detecting physiological changes, but it can also lead to an increased susceptibility to external noise and interference [95,110,111]. This issue becomes especially important in the context of wearable sensors and implantable devices, where the environment may be subject to electromagnetic interference, mechanical vibrations, and other disturbances that affect sensor accuracy. In order to improve the selectivity and sensitivity of EAP sensors, it is necessary to implement advanced signal processing techniques, such as filtering and noise cancelation algorithms, along with the integration of smart materials that can actively adjust to changing environmental conditions [20,112]. Additionally, improvements in sensor architecture, such as the development of hybrid systems that combine EAPs with other materials like graphene or metal nanoparticles, can further enhance the performance of these biosensors.

6.4. Scalability and Manufacturing Challenges

Large-Scale Production and Cost-Effectiveness

The scalability of EAP-based systems and the cost-effectiveness of their manufacturing processes are major hurdles in their commercialization, particularly in the healthcare and biomedical sectors. Currently, the fabrication of EAP devices is often performed on a small scale, using specialized techniques such as solution casting, electrospinning, or 3D printing. These methods are often time-consuming and costly, making it difficult to produce devices on a large scale. Moreover, achieving uniformity and consistency in the properties of EAPs across large batches is challenging, especially when integrating complex nanomaterials. To overcome these challenges, there is a need for scalable and cost-effective production methods that can maintain the high performance and quality of EAP devices on industrial scales. Advances in roll-to-roll printing techniques, automated manufacturing processes, and scalable polymer synthesis are essential to enable the widespread adoption of EAP-based devices in the market [113,114]. Additionally, the development of cost-effective materials and the optimization of production techniques could make these devices affordable and accessible for use in various applications, including personal healthcare, diagnostics, and rehabilitation. Ultimately, while electroactive polymers offer significant potential for self-powered actuators and biosensors in biomedical applications, several challenges remain that must be addressed to fully realize their capabilities. These include material durability, power generation efficiency, signal optimization, and scalability in manufacturing. Addressing these challenges through continued innovation in material science, energy harvesting technologies, signal processing, and manufacturing techniques will be key to enabling the next generation of EAP-based systems in healthcare.

Table 5. Comparative overview of challenges and limitations in EAP-based systems.

Challenges and Limitations	Key Issues	Recent Advances/Research	Ref.
Material durability and stability	Long-term performance and biocompatibility concerns. EAPs degrade over time due to mechanical stress and environmental factors. Nanomaterial integration may introduce toxicity.	Development of surface modifications, protective coatings, and new stable materials. Use of biocompatible coatings and nanomaterials for improved safety.	[115]
Power generation and storage efficiency	Energy harvesting mechanisms often have limited output and efficiency. Integrating efficient energy storage systems is challenging.	Advances in energy storage, such as supercapacitors and flexible batteries. Optimization of energy harvesting systems for continuous operation.	[116]
Signal optimization and noise reduction	High sensitivity of EAP sensors leads to noise and interference, affecting accuracy. Environmental disturbances can impact sensor readings.	Advanced signal processing techniques, such as filtering and noise cancelation. Hybrid systems with smart materials for improved performance.	[117]
Scalability and manufacturing challenges	Difficulty in large-scale production and maintaining uniformity. High cost of fabrication.	Scalable manufacturing techniques such as roll-to-roll printing. Development of cost-effective production methods and optimized polymer synthesis.	[118]

presents a comparative overview of the key challenges and limitations associated with electroactive polymer (EAP)-based systems, particularly focusing on material durability, energy generation and storage efficiency, signal optimization, and scalability [115,116,117,118]. The material durability and stability of EAPs remain significant hurdles, as prolonged mechanical stress and exposure to environmental factors lead to degradation, impacting their long-term performance. To mitigate this, advancements such as surface modifications, protective coatings, and biocompatible nanomaterial integration are being explored to enhance durability and safety in biomedical applications [119,120]. In terms of energy generation, the efficiency of energy harvesting remains a challenge, with limited output from conventional piezoelectric and triboelectric mechanisms. Recent efforts in optimizing energy storage technologies, like supercapacitors and flexible batteries, have aimed to improve the continuous operation of self-powered systems [121]. Signal optimization also poses a significant challenge due to the high sensitivity of EAP sensors, which makes them susceptible to noise and external interference. Advanced signal processing techniques and the development of hybrid systems with smart materials offer promising solutions to enhance the selectivity and sensitivity of these sensors [39]. Finally, scalability and cost-effectiveness in manufacturing are critical factors for the commercial viability of EAP-based systems. The exploration of scalable techniques like roll-to-roll printing and the optimization of polymer synthesis processes are steps toward overcoming these challenges, making the large-scale production of EAP devices feasible and affordable [20,114]. The table underscores the need for continued research and innovation to address these challenges, ensuring that EAP-based systems can reach their full potential in biomedical applications.

7. Clinical Translation and Future Perspectives

The potential of electroactive polymers (EAPs) in biomedical applications is immense, ranging from self-powered actuators for soft robotics to highly sensitive biosensors for real-time health monitoring. However, despite their promising capabilities, significant barriers exist in terms of clinical adoption, regulatory approval, and integration into existing healthcare infrastructures. This section discusses the pathways for the clinical translation of EAP-based devices, regulatory considerations for implantable and wearable devices, emerging trends in personalized medicine and smart healthcare, and future research directions to overcome the current limitations in EAP-driven biomedical technologies.

7.1. Pathways for the Clinical Adoption of EAP-Based Devices

The clinical adoption of EAP-based devices requires overcoming significant technical, regulatory, and clinical barriers. One of the first challenges is the demonstration of the safety and efficacy of these devices in real-world applications. For EAP-based sensors and actuators to be adopted in clinical practice, their performance must be verified through extensive preclinical and clinical trials. Furthermore, collaborations between academic institutions, industry, and healthcare providers are crucial to accelerating the development and integration of EAP-based systems into medical devices. The pathways to clinical adoption involve addressing key issues such as durability, biocompatibility, and manufacturability, while ensuring that the devices meet the required standards for medical equipment. Clinical trials will also play a vital role in evaluating the long-term effects of these devices in patients, particularly for implantable systems. Once these challenges are overcome, EAP-based devices will find their place in a variety of applications, including wearable health monitors, rehabilitation devices, and personalized healthcare systems [122].

7.2. Regulatory Considerations for Implantable and Wearable Devices

The integration of EAPs into implantable and wearable medical devices requires rigorous adherence to the regulatory standards set by health authorities such as the U.S. Food and Drug Administration (FDA) or the European Medicines Agency (EMA). The regulatory process involves several stages, including safety and biocompatibility testing, performance evaluations, and clinical validation. For implantable devices, such as artificial muscles or biosensors, additional concerns regarding long-term biointegration, material degradation, and immune responses must be addressed. Wearable EAP-based devices, on the other hand, must meet specific requirements for user safety, comfort, and durability in continuous use. The use of nanomaterials, which are often incorporated into EAP systems, introduces additional regulatory complexity, particularly concerning toxicity and environmental impact. To navigate these regulatory hurdles, interdisciplinary teams comprising material scientists, biomedical engineers, and regulatory experts will be necessary to ensure that EAP devices comply with the required standards for approval [123]. Moreover, clear guidelines for the certification and standardization of EAP-based devices are essential to promote their widespread use in clinical settings. In implantable biomedical applications, EAPs such as ionic polymer–metal composites (IPMCs), dielectric elastomers (DEs), and conductive polymers like polypyrrole (PPy) and polyaniline (PANI) have shown distinct advantages depending on the functional requirement. For instance, dielectric elastomers exhibit high actuation strain (up to 380%) and fast response times, making them suitable for artificial muscles and dynamic mechanical interfaces [39]. Conversely, IPMCs, which operate at low voltages (<5V), provide finer movement control and biocompatibility, but with lower actuation force (<1 N), limiting their utility in high-load applications. For biosensing purposes, conductive polymers such as PPy offer detection limits in the nanomolar range for biomarkers like glucose and dopamine, with sensitivities exceeding 100 µA/mM·cm², enabling real-time and in situ biochemical monitoring [124]. However, their electrochemical stability over prolonged implantation remains a regulatory concern due to potential degradation by bodily fluids. Therefore, choosing a suitable EAP system involves a trade-off between actuation performance, sensing sensitivity, stability, and compliance with biocompatibility standards like ISO 10993. For wearable devices, the performance metrics often emphasize mechanical flexibility, stretchability, energy conversion efficiency, and user safety. Piezoelectric EAP composites integrated into flexible substrates have demonstrated power outputs ranging from 0.5 to 3.2 µW/cm² under normal human motion, which is adequate for powering low-energy biosensors or data transmission modules [20,47]. Additionally, triboelectric-based EAPs used in self-powered wearable sensors show voltage outputs of up to 200 V and current densities of 5 µA/cm² during repetitive motion cycles, such as walking or hand gestures [125]. Despite these promising figures, challenges remain in achieving consistent performance across varying environmental conditions such as humidity, temperature, and mechanical fatigue. From a regulatory perspective, these variations must be addressed during performance evaluations to ensure reliability in real-world settings. Furthermore, the lack of standardized metrics for comparing EAP-based devices poses a significant barrier in regulatory submissions. Establishing a benchmark framework with quantifiable metrics such as actuation force per unit volume, energy density, and durability (number of cycles to failure) is essential to facilitate cross-comparison and the regulatory approval of these innovative systems.

7.3. Emerging Trends in Personalized Medicine and Smart Healthcare

The integration of EAP-based systems into personalized medicine and smart healthcare is one of the most exciting prospects for the future of medical diagnostics and treatment. EAP-based biosensors, due to their high sensitivity and real-time monitoring capabilities, can enable the continuous health monitoring of physiological parameters, including glucose levels, lactate, and heart rate, providing invaluable data for individualized treatment plans. The advent of wearable health monitoring devices, powered by EAPs, offers the possibility of real-time feedback to both patients and healthcare providers, enabling the timely adjustment of therapeutic regimens. Furthermore, EAP-driven systems have the potential to integrate with other advanced technologies, such as artificial intelligence (AI) and machine learning, to create smarter, adaptive healthcare systems. This integration can provide predictive analytics for disease progression, personalized drug delivery, and the early detection of health anomalies. As personalized medicine continues to grow, EAP-based devices will become an integral part of the personalized healthcare ecosystem, facilitating individualized care plans and improving patient outcomes [71,126]. Recent advancements in electroactive polymer-based biosensors have demonstrated measurable improvements in the performance metrics aligned with the needs of personalized medicine. For instance, stretchable polypyrrole-based glucose sensors have achieved sensitivities of up to 150 µA/mM·cm² and detection limits as low as 5 µM, outperforming traditional rigid sensors in dynamic physiological environments [127]. Similarly, PANI-based strain sensors embedded in wearable patches have demonstrated gauge factors exceeding 10³, with detection ranges from 0.1% to 100% strain, allowing for the precise biomechanical tracking of joint and muscle movement critical in rehabilitation monitoring and injury prevention [128]. Compared to conventional silicon-based biosensors, EAP-enabled devices offer superior conformability and mechanical matching with soft tissues, reducing signal artifacts and enhancing user comfort during continuous wear. These quantitative advancements make EAPs particularly valuable for long-term, non-invasive monitoring systems integrated into personalized care platforms. Furthermore, EAPs are enabling real-time physiological monitoring with feedback control loops that adapt to user-specific health metrics, creating a closed-loop personalized healthcare model. For example, dielectric elastomer actuators integrated into insulin delivery systems have been shown to deliver on-demand insulin micro-doses in response to the real-time glucose levels monitored by embedded EAP biosensors [39]. When coupled with AI algorithms trained on patient-specific data, these systems can preemptively adjust dosing to prevent glycemic excursions. Similar frameworks are being developed for cardiovascular monitoring and neuromuscular diagnostics. However, widespread clinical integration requires the robust validation of long-term sensor stability (e.g., >90% accuracy over 30 days), low power consumption (<10 µW for continuous operation), and user adaptability in diverse physiological conditions. Therefore, future EAP-enabled personalized healthcare systems will likely evolve into modular, AI-enhanced platforms where multi-modal sensing, actuation, and therapeutic responses are tightly integrated to offer patient-specific, predictive, and preventative medical interventions.

7.4. Future Research Directions for EAP-Driven Biomedical Technologies

Despite significant progress in the development of EAP-based systems for biomedical applications, many challenges remain that require further research and innovation. Future research efforts should focus on improving the energy harvesting efficiency and storage capabilities of EAP-based systems, especially for self-powered devices used in remote monitoring and implantable systems. Moreover, enhancing the biocompatibility, long-term stability, and reliability of EAPs is crucial for their successful integration into clinical practice. Research into novel materials and composites, such as bio-based polymers, conductive nanomaterials, and biodegradable EAPs, will also be key to advancing these technologies. Additionally, the integration of EAP systems with advanced technologies like nanorobotics, bioelectronics, and artificial intelligence holds great potential for creating efficient, intelligent, and autonomous biomedical devices. Lastly, collaboration between researchers, clinicians, and regulatory bodies will play a vital role in addressing the challenges of clinical translation, ensuring that EAP-based biomedical technologies can be safely and effectively deployed in healthcare settings. Continued investment in fundamental research and translational studies will accelerate the path to realizing the full potential of EAP-based systems in personalized medicine and beyond [129]. EAP-based systems hold enormous potential for revolutionizing biomedical diagnostics and healthcare. However, their clinical translation will require addressing numerous challenges related to safety, performance, regulatory compliance, and integration into personalized healthcare systems. By advancing research in materials science, energy harvesting, and signal processing, and by navigating the regulatory landscape, EAP-based devices will be poised to become a cornerstone of future smart healthcare solutions. The current methods for evaluating EAP-driven biomedical technologies often rely on qualitative descriptions or isolated case studies, lacking consistent quantitative data such as energy conversion efficiency, actuation strain, response time, sensitivity, and durability under physiological conditions. This inconsistency hampers the ability to make direct comparisons between competing materials and device architectures. Moreover, many studies fail to report standardized testing conditions, making it difficult to benchmark performance across different platforms. Future research should prioritize the development of standardized evaluation protocols and comprehensive datasets that enable objective comparisons and meta-analyses. Incorporating these quantitative benchmarks will not only clarify the true potential of various EAP systems, but also guide the optimization of materials and device configurations for specific biomedical applications.

8. Conclusion

8.1. Summary of Key Findings and Innovations

This review highlights the transformative potential of electroactive polymers (EAPs) in revolutionizing biomedical diagnostics and healthcare applications. EAPs, due to their unique ability to convert electrical signals into mechanical motion, have emerged as critical components in self-powered actuators and biosensors. Their integration into soft robotics and biohybrid systems, along with their application in artificial muscles, prosthetics, and rehabilitation devices, demonstrates significant progress in creating devices that closely mimic biological systems. In addition, the ability of EAP-based sensors to harvest energy from physiological processes enables continuous monitoring without external power sources, thereby enhancing patient comfort and compliance. Innovations in materials science, such as the incorporation of nanomaterials like carbon nanotubes, graphene, and metal nanoparticles, have significantly improved the sensitivity, durability, and biocompatibility of EAP systems. These advancements have not only improved the energy harvesting efficiency of EAP-based systems, but also expanded their potential for use in wearable and implantable devices. Furthermore, the combination of flexible electronics with EAPs has facilitated the development of non-invasive and real-time health monitoring devices that can continuously track biomarkers such as glucose, lactate, and other physiological signals. The future of EAP-driven technologies also includes promising applications in point-of-care diagnostics and personalized medicine, which have the potential to revolutionize healthcare delivery.

8.2. Impact on the Future of Biomedical Diagnostics and Healthcare Technologies

The integration of EAP-based systems into healthcare technologies is set to have a profound impact on biomedical diagnostics and personalized healthcare. As self-powered sensors and actuators continue to evolve, they will enable the accurate, real-time monitoring of patient health with minimal intervention. This shift toward continuous, non-invasive health monitoring will not only improve the early detection of diseases, but also enable personalized and responsive treatment regimens. With the advancement of EAP materials, systems will become robust, energy-efficient, and capable of withstanding long-term use in challenging environments. The adoption of EAPs in wearable and implantable devices will further transform medical devices, making them adaptable, intelligent, and responsive to individual patient needs. As these devices become integrated with digital health systems, they will play a critical role in the development of smart healthcare solutions. Moreover, the ability of EAP systems to operate in remote or resource-limited settings without requiring frequent recharging or external power sources will expand their use in underserved populations and low-resource areas. Looking ahead, continued research into the optimization of energy harvesting mechanisms, material durability, and signal processing will drive the next generation of EAP-based technologies. The combination of advanced EAP materials, smart sensors, and artificial intelligence will open new avenues for personalized medicine, predictive diagnostics, and tailored therapeutic interventions. Ultimately, EAP-based systems hold the potential to not only advance the field of biomedical diagnostics, but also reshape the entire healthcare landscape, making healthcare accessible, efficient, and patient-centered.