Search Results (30)

This paper comprehensively reviews sensors and sensing devices developed or/and proposed so far utilizing two smart materials: electrorheological fluids (ERFs) and magnetorheological materials (MRMs) whose rheological characteristics such as stiffness and damping can be controlled by external stimuli; an electrical voltage for ERFs and a magnetic field for MRMs, respectively. In this review article, the MRMs are classified into magnetorheological fluids (MRF), magnetorheological elastomers (MRE) and magnetorheological plastomers (MRP). To easily understand the history of sensing research using these two smart materials, the order of this review article is organized in a chronological manner of ERF sensors, MRF sensors, MRE sensors and MRP sensors. Among many sensors fabricated from each smart material, one or two sensors or sensing devices are adopted to discuss the sensing configuration, working principle and specifications such as accuracy and sensitivity. Some sensors adopted in this article include force sensors, tactile devices, strain sensors, wearable bending sensors, magnetometers, display devices and flux measurement sensors. After briefly describing what has been reviewed in a conclusion, several challenging future works, which should be undertaken for the practical applications of sensors or/and sensing devices, are discussed in terms of response time and new technologies integrating with artificial intelligence neural networks in which several parameters affecting the sensor signals can be precisely and optimally tuned. It is sure that this review article is very helpful to potential readers who are interested in creative sensors using not only the proposed smart materials but also different types of smart materials such as shape memory alloys and active polymers. Full article

Shape memory and self-healing polymer nanocomposites have attracted considerable attention due to their modifiable properties and promising applications. The incorporation of nanomaterials (polypyrrole, carboxyl methyl cellulose, carbon nanotubes, titania nanotubes, graphene, graphene oxide, mesoporous silica) into these polymers has significantly enhanced their performance, opening up new avenues for diverse applications. The self-healing capability in polymer nanocomposites depends on several factors, including heat, quadruple hydrogen bonding, π–π stacking, Diels–Alder reactions, and metal–ligand coordination, which collectively govern the interactions within the composite materials. Among possible interactions, only quadruple hydrogen bonding between composite constituents has been shown to be effective in facilitating self-healing at approximately room temperature. Conversely, thermo-responsive self-healing and shape memory polymer nanocomposites require elevated temperatures to initiate the healing and recovery processes. Thermo-responsive (TRSMPs), light-actuated, magnetically actuated, and Electrically actuated Shape Memory Polymer Nanocomposite are discussed. This paper provides a comprehensive overview of the different types of interactions involved in SMP and SHP nanocomposites and examines their behavior at both room temperature and elevated temperature conditions, along with their biomedical applications. Among many applications of SMPs, special attention has been given to biomedical (drug delivery, orthodontics, tissue engineering, orthopedics, endovascular surgery), aerospace (hinges, space deployable structures, morphing aircrafts), textile (breathable fabrics, reinforced fabrics, self-healing electromagnetic interference shielding fabrics), sensor, electrical (triboelectric nanogenerators, information energy storage devices), electronic, paint and self-healing coating, and construction material (polymer cement composites) applications. Full article

Biological species can walk, swim, fly, jump, and climb with fast response speeds and motion complexity. These remarkable functions are accomplished by means of soft actuation organisms, which are commonly composed of muscle tissue systems. To achieve the creation of their biomimetic artificial counterparts, various biomimetic stimuli-responsive materials have been synthesized and developed in recent decades. They can respond to various external stimuli in the form of structural or morphological transformations by actively or passively converting input energy into mechanical energy. They are the core element of soft actuators for typical smart devices like soft robots, artificial muscles, intelligent sensors and nanogenerators. Significant progress has been made in the development of bioinspired stimuli-responsive materials. However, these materials have not been comprehensively summarized with specific actuation mechanisms in the literature. In this review, we will discuss recent advances in biomimetic stimuli-responsive materials that are instrumental for soft actuators. Firstly, different stimuli-responsive principles for soft actuators are discussed, including fluidic, electrical, thermal, magnetic, light, and chemical stimuli. We further summarize the state-of-the-art stimuli-responsive materials for soft actuators and explore the advantages and disadvantages of using electroactive polymers, magnetic soft composites, photo-thermal responsive polymers, shape memory alloys and other responsive soft materials. Finally, we provide a critical outlook on the field of stimuli-responsive soft actuators and emphasize the challenges in the process of their implementation to various industries. Full article

The acceleration in advancements of smart materials and non-contact controlled devices in the field of 4D printing is facilitated by the use of magnetically responsive shape memory polymer (SMP) composites. This study is dedicated to the development of promising shape memory materials based on polylactic acid (PLA) and cobalt ferrite (CoFe₂O₄) nanoparticles. The activation of the shape memory effect (SME) in magnetic nanoparticle composites was achieved by applying a high-frequency alternating magnetic field (HFAMF). The PLA/CoFe₂O₄ composites exhibited a remarkable shape recovery ratio (>84%) and underwent rapid heating when exposed to HFAMF. The interaction of these composites with mouse adipose-derived mesenchymal stem cells demonstrated adequate cytocompatibility. The rapid magnetosensitive behavior and high shape recovery characteristics of PLA/CoFe₂O₄ composites make them promising candidates for biomedical applications. Full article

In 4D printing, an additively manufactured component is given the ability to change its shape or function in an intended and useful manner over time. The technology of 4D printing is still in an early stage of development. Nevertheless, interesting research and initial applications exist in the literature. In this work, a novel methodical approach is presented that helps transfer existing 4D printing research results and knowledge into solving application tasks systematically. Moreover, two different smart materials are analyzed, used, and combined following the presented methodical approach to solving the given task in the form of recovering an object from a poorly accessible space. This is implemented by self-positioning, grabbing, and extracting the target object. The first smart material used to realize these tasks is a shape-memory polymer, while the second is a polymer-based magnetic composite. In addition to the presentation and detailed implementation of the methodical approach, the potentials and behavior of the two smart materials are further examined and narrowed down as a result of the investigation. The results show that the developed methodical approach contributes to moving 4D printing closer toward a viable alternative to existing technologies due to its problem-oriented nature. Full article

To meet the great requirements of future technologies, such as robots, single-crystal (SC) Ni-Mn-Ga alloys and their composites were designed and investigated in this study. Ferromagnetic shape memory alloys (FSMAs) are promising materials for applications in high-speed actuators, which are core components of robots; however, there are some issues of embrittlement and small deformation strain. Therefore, in this work, we first prepared SC Ni-Mn-Ga alloys for fundamental investigations of the shape deformations under the application of different fields (e.g., compressive and magnetic fields). Second, the SC Ni-Mn-Ga alloys were integrated with polymers of epoxy resin or silicone rubber to solve the embrittlement problem. The obvious two-stage yielding and sudden intensifying of the magnetization both suggest martensite variant reorientation (MVR) under the compressive and magnetic fields, respectively. Micro-computed tomography (μCT) and an X-ray diffractometer were utilized for the observations of shape deformation brought about by the MVR of the SC Ni-Mn-Ga particles in the polymer matrix. Clear MVR and shape deformation could be found in the compressed composites. Full article

In polymer systems, induction heating (IH) is the physical outcome that results from the exposure of selected polymer composites embedding electrically-conductive and/or ferromagnetic fillers to an alternating electromagnetic field (frequency range: from kHz to MHz). The interaction of the applied electromagnetic field with the material accounts for the creation of magnetic polarization effects (i.e., magnetic hysteresis losses) and/or eddy currents (i.e., Joule losses, upon the formation of closed electrical loops), which, in turn, cause the heating up of the material itself. The heat involved can be exploited for different uses, ranging from the curing of thermosetting systems, the welding of thermoplastics, and the processing of temperature-sensitive materials (through selective IH) up to the activation of special effects in polymer systems (such as self-healing and shape-memory effects). This review aims at summarizing the current state-of-the-art of IH processes for polymers, providing readers with the current limitations and challenges, and further discussing some possible developments for the following years. Full article

In this first volume, we cover relevant aspects of chemical and physical processes of the production and characterization of magnetic materials in bulk, thin films, nanostructures, and/or nanocomposites, as well as modeling aspects involving such structures. Accordingly, this volume presents eleven original research and review works on the challenges and trends covering fundamental and experimental work, with a special focus on the design, synthesis, and characterization of various types of magnetic materials, and the study of their structure–property relationships. State-of-the-art results on the development of new experimental concepts, leading to the transfer, chemical transformation, and high-resolution patterning of advanced thin films and nanomaterials, and to the design and fabrication of devices, are also presented and discussed. Full article

The objective of this review is to investigate the potential of functionalized magnetic polymer composites for use in electromagnetic micro-electro-mechanical systems (MEMS) for biomedical applications. The properties that make magnetic polymer composites particularly interesting for application in the biomedical field are their biocompatibility, their adjustable mechanical, chemical, and magnetic properties, as well as their manufacturing versatility, e.g., by 3D printing or by integration in cleanroom microfabrication processes, which makes them accessible for large-scale production to reach the general public. The review first examines recent advancements in magnetic polymer composites that possess unique features such as self-healing capabilities, shape-memory, and biodegradability. This analysis includes an exploration of the materials and fabrication processes involved in the production of these composites, as well as their potential applications. Subsequently, the review focuses on electromagnetic MEMS for biomedical applications (bioMEMS), including microactuators, micropumps, miniaturized drug delivery systems, microvalves, micromixers, and sensors. The analysis encompasses an examination of the materials and manufacturing processes involved and the specific fields of application for each of these biomedical MEMS devices. Finally, the review discusses missed opportunities and possible synergies in the development of next-generation composite materials and bioMEMS sensors and actuators based on magnetic polymer composites. Full article

Movements in plants, such as the coiling of tendrils in climbing plants, have been studied as inspiration for coiling actuators in robotics. A promising approach to mimic this behavior is the use of multimaterial systems that show different elastic moduli. Here, we report on the development of magnetically controllable/triggerable multimaterial fibers (MMFs) as artificial tendrils, which can reversibly coil and uncoil on stimulation from an alternating magnetic field. These MMFs are based on deformed shape-memory fibers with poly[ethylene-co-(vinyl acetate)] (PEVA) as their core and a silicone-based soft elastomeric magnetic nanocomposite shell. The core fiber provides a temperature-dependent expansion/contraction that propagates the coiling of the MMF, while the shell enables inductive heating to actuate the movements in these MMFs. Composites with mNP weight content ≥ 15 wt% were required to achieve heating suitable to initiate movement. The MMFs coil upon application of the magnetic field, in which a degree of coiling N = 0.8 ± 0.2 was achieved. Cooling upon switching OFF the magnetic field reversed some of the coiling, giving a reversible change in coiling ∆n = 2 ± 0.5. These MMFs allow magnetically controlled remote and reversible actuation in artificial (soft) plant-like tendrils, and are envisioned as fiber actuators in future robotics applications. Full article

In 2020, we published a review on the study of semi-crystalline thermoplastic polyurethane elastomers and composites based on the shape memory effect. The shape recovery ability of such polymers is determined by their sensitivity to temperature, moisture, and magnetic or electric fields, which in turn are dependent on the chemical properties and composition of the matrix and the nanofiller. Nanocellulose is a type of nanomaterial with high strength, high specific surface area and high surface energy. Additionally, it is nontoxic, biocompatible, environmentally friendly, and can be extracted from biomass resources. Thanks to these properties, nanocellulose can be used to enhance the mechanical properties of polymer matrices with shape memory effect and as a switching element of shape memory. This review discusses the methods for producing and properties of nanocellulose-based thermo-, moisture-, and pH-sensitive polyurethane composites. The synergistic effect of nanocellulose and carbon nanofillers and possible applications of nanocellulose-based thermoplastic polyurethane biocomposites with shape memory effect are discussed. A brief description of nanocellulose terminology is also given, along with the structure of shape memory thermoplastic polyurethanes. There is significant interest in such materials for three primary reasons: the possibility of creating a new generation of biomaterials, improving the environmental friendliness of existing materials, and exploiting the natural renewability of cellulose sources. Full article

Shape memory nanocomposites are excellent smart materials which can switch between a variable temporary shape and their original shape upon exposure to external stimuli such as heat, light, electricity, magnetic fields, moisture, chemicals, pH, etc. Numerous nanofillers have been introduced in shape memory polymers such as carbon nanotubes, graphene, nanodiamonds, carbon nanofibers, etc. Among nanocarbons, graphene has attracted research interest for the development of shape memory polymer/graphene nanocomposites. Graphene is a unique one-atom-thick two-dimensional nanosheet of sp²-hybridized carbon atoms. Graphene has been used as an effective nanofiller in shape memory polymeric nanocomposites owing to its remarkable electrical conductivity, flexibility, strength, and heat stability. Thermoplastics as well as thermoset matrices have been used to form the shape memory nanomaterials with graphene nanofiller. In shape memory polymer/graphene nanocomposites, their shape has been fixed above the transition temperature and then transformed to the original shape through an external stimulus. The inclusion of graphene in nanocomposites can cause fast switching of their temporary shape to their original shape. Fine graphene dispersion, matrix–nanofiller interactions, and compatible interface development can lead to high-performance shape memory graphene-derived nanocomposites. Consequently, this review focuses on an important class of shape memory graphene-based nanocomposites. The fabrication, physical properties, and shape memory actuation of polymer/graphene nanocomposites are discussed. The stimuli-responsive polymer/graphene nanocomposites mostly revealed heat-, electricity-, and light-induced effects. The inclusion of graphene enhanced the physical/covalent linking, shape recovery, shape fixity, flexibility, and crystallization effects in the polymers. Furthermore, potential applications of these materials are observed in the aerospace/automobile industries, civil engineering, and biomaterials. Full article

Flexible materials that provide an electric, magnetic, or optic response upon deformation or tactile pressure could be important for the development of smart monitors, intelligent textiles, or in the development of robotic skins. In this work we demonstrate the capabilities of a flexible and electrically conductive polymer material that produces an electrical response with any deformation, namely the electrical resistance of the material changes proportionally with the deformation pressure. Furthermore, the material exhibits a memory effect. When compressed beyond the elastic regime, it retains the memory of the plastic deformation by increasing its resistance. The material was obtained by in situ polymerization of semiconducting polyaniline (PANi) in a polyvinyl alcohol/glycerol (PVA/Gly) hydrogel matrix at −17 °C. Upon drying of the hydrogel, an elastomer composite is obtained, with rubber-like characteristics. When compressed/decompressed, the electrical resistance of the material exhibits an unusually long equilibration/relaxation time, proportional with the load applied. These phenomena indicate a complex relaxation and reconfiguration process of the PANi/PVA elastomer matrix, with the shape change of the material due to mechanical stress. Full article

Repeated use of intravenous infusions to deliver drugs can cause nerve damage, pain, and infection. There is an unmet need for a drug delivery method that administers drugs on demand for prolonged use. Here, we developed magnetically responsive shape memory polymers (SMPs) to enhance control over drug release. Iron oxide magnetic nanoparticles (mnps) were synthesized and incorporated into previously developed SMPs to enable magnetically induced shape memory effects that can be activated remotely via the application of an alternating magnetic field. These materials were tested for their shape memory properties (dynamic mechanical analysis), cytocompatibility (3T3 fibroblast viability), and tunable drug delivery rates (UV–VIS to evaluate the release of incorporated doxorubicin, 6-mercaptopurine, and/or rhodamine). All polymer composites had >75% cytocompatibility over 72 h. Altering the polymer chemistry and mnp content provided methods to tune drug release. Namely, linear polymers with higher mnp content had faster drug release. Highly cross-linked polymer networks with lower mnp content slowed drug release. Shape memory properties and polymer/drug interactions provided additional variables to tune drug delivery rates. Polymers that were fixed in a strained secondary shape had a slower release rate compared with unstrained polymers, and hydrophobic drugs were released more slowly than hydrophilic drugs. Using these design principles, a single material with gradient chemistry and dual drug loading was synthesized, which provided a unique mechanism to deliver two drugs from a single scaffold with distinct delivery profiles. This system could be employed in future work to provide controlled release of selected drug combinations with enhanced control over release as compared with previous approaches. Full article

Three-dimensional printing enables building objects shaped with a large degree of freedom. Additional functionalities can be included by modifying the printing material, e.g., by embedding nanoparticles in the molten polymer feedstock, the resin, or the solution used for printing, respectively. Such composite materials may be stronger or more flexible, conductive, magnetic, etc. Here, we give an overview of magnetic composites, 3D-printed by different techniques, and their potential applications. The production of the feedstock is described as well as the influence of printing parameters on the magnetic and mechanical properties of such polymer/magnetic composites. Full article