Search Results (1,582)

Sensitivity and effective sensing range are core performance metrics of flexible pressure sensors, directly dictating their practical applicability. A key challenge in sensor design is sensitivity degradation with elevated pressure, hindering synergistic optimization of high sensitivity and broad sensing range, while cumbersome electrode fabrication further impedes facile preparation and large-scale deployment of high-performance devices. Herein, this work proposes a novel fabrication strategy for flexible iontronic pressure sensors via direct laser writing (DLW) technology. A controllable ultraviolet laser patterns polyimide substrates to fabricate hierarchical stepped conoid-like microstructural templates, which are transferred to ion gels through reverse molding. The DLW-enabled precise geometric control and hierarchical conical architectures efficiently amplify interfacial contact area variation under pressure, significantly boosting sensitivity. The resultant sensor achieves a high sensitivity of 118.4 kPa⁻¹ and a broad detection range up to 2000 kPa, with fast response/recovery times of 38.4 ms and 47 ms and excellent mechanical stability enduring 2000 loading–unloading cycles at 850 kPa. Multi-scenario physiological signal monitoring validates its accurate capture of laryngeal vibrations and joint movements. This work establishes a straightforward, efficient microfabrication route for high-performance flexible iontronic sensors, accelerating their practical application in wearable health monitoring and related fields. Full article

Wearable electrodes have attracted attention for their ability to monitor human electrophysiological signals, such as those generated by the heart and captured via electrocardiography (ECG). In this study, an easy and scalable drop-coating method was used to develop flexible, dry, and sustainable ECG electrodes composed of a poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/polyvinyl alcohol/xanthan gum (PXP) composite. The electrodes were fabricated on different cellulosic substrates, such as Xuan paper, Kraft paper, and wheat bagasse, and further modified through the incorporation of MoO₃ (PXPM composite). PXP exhibits a broad absorption band of 350–550 nm, while PXPM shows a shifted band of 400–750 nm, due to the interaction of MoO₃ with PEDOT:PSS. The fluorescence emission of PXP appears at 443 nm, while the emission for PXPM is broader and centered at 437 nm. Electrically, both composites exhibit continuity and ohmic behavior. Microstructural analysis revealed that the interaction between the composite film and the substrate strongly influences pore formation, film uniformity, and the distribution of Mo species, highlighting the role of MoO₃ as an interfacial modifier that promotes smoother and more homogeneous coatings on selected cellulosic substrates. All fabricated electrodes demonstrated the capability to detect ECG signals with sufficient quality to be clinically valid. Full article

The rapid detection of organophosphorus (OP) compounds is crucial for safeguarding human health and ensuring food safety. This study presents a novel wearable electrochemical biosensor that integrates miniaturized screen-printed electrodes with wearable devices to achieve real-time, on-site OP detection. The biosensor was fabricated by constructing a screen-printed carbon electrode (SPCE) on a thermoplastic polyurethane (TPU) substrate, sequentially modified with graphene (GR), gold nanoparticles (AuNPs), and organophosphorus hydrolase (OPH), and finally encapsulated with Nafion. This SPCE/GR/AuNPs/OPH/Nafion configuration yields a highly flexible and portable device. The detection principle relies on the enzymatic hydrolysis of methyl paraoxon (MPOX) by OPH, generating p-nitrophenol (PNP), which is quantitatively measured via square wave voltammetry (SWV). The sensor exhibits a broad linear detection range (30–400 μM) with a strong linear correlation (R² = 0.995) and a low detection limit (0.321 μM). It demonstrates excellent selectivity against common interfering substances, including urea, sucrose, and various metal ions. Application to real-world samples such as cabbage and tap water yielded high recoveries (107.2% for cabbage and 101.2% for tap water), with relative standard deviations (RSDs) below 8%. Furthermore, the biosensor maintains robust flexibility and mechanical resilience, with less than 5% signal loss after 100 bending cycles, confirming its suitability for wearable applications and reliable operation under mechanical stress. This innovative, flexible electrochemical biosensor provides a powerful and reliable platform for rapid OP detection, particularly in complex testing environments. Full article

A bottom-up fabrication approach for flexible piezoelectric micromachined ultrasound transducer (PMUT) arrays on stainless-steel substrates was developed. Devices were fabricated using chemical solution deposition of a 700 nm-thick layer of Pb_0.99□_0.01(Zr_0.52Ti_0.48)Nb_0.02O₃, where □ denotes a vacancy on the Pb site, on 50 μm-thick LaNiO₃/HfO₂/stainless-steel foils. Lithography for definition of the electrode and piezoelectric layers was completed on the front of the wafer. Ni electroplating on the back side of the foil was used to create locally stiff areas to define the deflection area. PMUT devices were successfully fabricated using this method. The permittivity and loss tangent of the fabricated device at 1 kHz were 283 ± 9 and <1.5%, respectively. The remanent polarization was measured to be 38 ± 0.3 μC/cm². Full article

In this paper, a drive–vibration integrated piezoelectric actuator (DVIPA) is proposed for vibration-assisted implantation of flexible electrodes. Conventional implantation systems typically rely on separate actuation and vibration modules, which increase system complexity and limit integration. To address this limitation, the proposed DVIPA integrates driving and vibration functions within a single compact structure by employing two piezoelectric bimorphs for clamping and a piezoelectric stack for combined actuation. A composite excitation waveform, consisting of high-frequency sinusoidal signals superimposed on the rising stage of a low-frequency trapezoidal wave, is applied to simultaneously generate forward motion and vibration. This configuration enables a coupled motion mode that facilitates insertion while reducing the risk of buckling. A prototype of the DVIPA was developed and experimentally evaluated. The results show that vibration-assisted implantation can be achieved under various operating conditions, with independently adjustable driving and vibration parameters. A maximum speed of 328 μm/s is obtained, meeting the requirements for flexible electrode implantation. Agarose gel experiments further demonstrate that vibration frequencies above 40 Hz and voltages between 20 and 40 V can effectively assist implantation of polydimethylsiloxane (PDMS) without buckling failure. Overall, the proposed actuator provides a compact and integrated solution for vibration-assisted implantation, offering potential advantages in applications with limited space. Full article

Background: The growing demand for sustainable, high-performance energy storage systems has intensified interest in biomass-derived materials for supercapacitor applications. This study presents a green and scalable approach to fabricating novel electrodes and solid-state electrolytes using Phoenix dactylifera (Ajwa date) seed biomass and palm waste-derived activated carbon. Methods: KOH-activated carbon from date pits was employed to enhance surface area and redox activity. A double-network hydrogel electrolyte (DSHC) was synthesized by incorporating 0.5 g of date seed powder with sodium alginate and wheat starch (0.2 g each), followed by chemical crosslinking in 2 M H₂SO₄. Structural and physicochemical properties were analyzed using SEM, XRD, and FTIR, while electrochemical performance was evaluated through cyclic voltammetry and galvanostatic charge–discharge measurements. Results: SEM revealed a densely ordered porous network with regular cylindrical channels favorable for ion transport. XRD and FTIR confirmed amorphous carbon formation and effective molecular crosslinking. The hydrogel electrolyte exhibited a wide potential window of ~2 V and strong pseudocapacitive behavior, delivering a maximum specific capacitance of 179 F g⁻¹ at 5 mV s⁻¹ and a discharge capacitance of 159 F g⁻¹ at 0.2 A g⁻¹, with excellent stability over 5500 cycles. Conclusions: Agricultural waste-derived materials demonstrate strong potential as low-cost, eco-friendly, and mechanically robust components for flexible supercapacitors, suitable for sustainable energy storage and rapid-charging applications. Full article

Electrochromic devices have emerged as promising candidates for non-emissive displays due to their particular photoelectric performance in complex lighting environments. They exhibit considerable potential in emerging fields such as Internet of Things terminals, flexible wearables and human–computer interaction interfaces. In this study, we developed a low-power electrochromic display based on a Pt/FTO (Fluorine doped tin oxide) electrocatalytic counter electrode and a Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) porous gel electrolyte. The Pt catalyst enhances Br⁻/Br³⁻ redox reactivity, which reduces the driving voltage from 2 V to 1 V, and accelerates the electrode reaction kinetics. It is systematically explained by the Density Functional Theory (DFT) calculations and electrochemical characterization. Furthermore, we demonstrate a proof-of-concept multicolor display incorporating the electrocatalytic counter electrode with various viologen derivatives. This approach provides a significant advancement toward next-generation high-performance displays and is supportive of the development of energy-efficient optoelectronic devices. Full article

With the rapid development of smart devices for body area networks and smart packaging, there is a significant demand for low-waste and low-impact electronic systems in industries such as healthcare and transportation. We demonstrate that the dielectric material from capacitors in resistor-inductor-capacitor (RLC) wireless, chipless, resonant temperature sensors can be successfully recovered from flexible PCBs, with pristine sensors re-introduced to the tag’s sensor loading. First, we demonstrate that replacing the dielectric in a parallel plate capacitor with a pristine component, with recycled electrodes and sub-miniature-A (SMA) adaptor, results in only a 3% change in broadband capacitance. An identical substitution of the sensing element in an RLC circuit tuned to resonate at 21.0 MHz, with recycled parallel plates, a resistor, and an inductive PCB coil, results in a change of only 7.6% in the resonant frequency of the tag to 19.4 MHz. This work demonstrates the recyclability of chipless tags for temperature sensing for the first time, offering sustainability gains in smart packaging applications, with the potential to be expanded to other sensing tags for pH, humidity, and chemical analytes, towards chipless product passports. Full article

Benefiting from their outstanding porosity, considerable specific surface area, and natural flexibility, cellulose nanofibers (CNFs)/MOF materials have emerged as competitive candidates for advanced flexible energy storage devices. However, conventional CNFs/MOFs aerogels or films often suffer from poor recoverability under compression, bending, and folding, accompanied by severe plastic deformation that compromises the cycling and structural stability of devices. To address this issue, we report a rationally designed flexible PU/CNFs/ZIF-8/PANI composite foam with an interconnected micro-mesoporous structure. Using polyurethane foam as a soft substrate and CNFs/ZIF-8 as building blocks, the composite was fabricated through a combined strategy of impregnation, in situ ZIF-8 growth, hot-pressing, and in situ aniline polymerization with simultaneous etching of the ZIF-8. The incorporation of carboxylated CNFs enhances the hydrophilicity of the PU skeleton. This, in combination with the hot-pressed framework, establishes an interconnected 3D network, thereby effectively preventing the agglomeration of active materials. Meanwhile, the hierarchical pores derived from the sacrificial ZIF-8 template provide abundant electroactive sites, accelerate ion transport, and facilitate high PANI loading. By virtue of this synergistic architectural effect, the resultant electrode achieves a high specific capacitance of 449 F/g at 0.2 A/g, with 97% capacitance retention after 2000 cycles at 5 A/g. Furthermore, the composite foam demonstrates excellent mechanical flexibility, with a tensile strength of 0.87 MPa and an elongation at break of 230%. This work offers a feasible approach for developing high-performance flexible supercapacitors and provides novel perspectives for the rational design of portable energy storage devices. Full article

To meet the requirements of flexibility and high performance for energy storage devices in flexible wearable electronic equipment, the MnO₂/acetylene black composite flexible cathodes is fabricated via 3D printing technology and the aqueous manganese-based zinc-ion flexible batteries are assembled. Based on bending and torsion mechanical tests, and the electrochemical tests, the optimal 3D printing electrode structure was determined. The micromorphology of the electrode after mechanical tests shows that when the printed lines of the upper and lower layers form a 30° angle, the electrode sheet exhibits the least damage. Electrochemical tests indicated that it had an ohmic resistance of 2.052 Ω, an interfacial charge transfer resistance of 141.1 Ω, a specific capacity of 103 mAh/g at 50 mA/g, and a specific capacity of 65 mAh/g at 500 mA/g. Compared with traditional coated electrodes, the 3D-printed electrode showed significantly improved diffusion coefficient, conductivity, and cycle stability. The assembled 3D-printed flexible battery could stably power a 1.5 V LED bulb under flat, bent, and twisted states. It provides a feasible solution for the development of high-performance flexible energy storage devices. Full article

Ionic polymer–metal composites consist of an ion-conducting polymer–gel membrane sandwiched between two flexible electrodes, representing a class of soft electroactive materials capable of large deformation under low voltage. The gel membrane, swollen with solvent, facilitates ion migration under an electric field, enabling actuation. Tailoring the interfacial architecture between the electrode and the polymer–gel membrane is pivotal for advancing high-performance IPMC actuators. This study presents a comparative investigation of three core–shell nanocomposite electrodes, fabricated via in situ polymerization, for IPMC applications. Among these, the polyaniline-coated multi-walled carbon nanotube composite exhibits a deliberately designed hierarchical structure, with a specific surface area of 32.345 m²·g⁻¹ and a conductive doped polyaniline shell, as confirmed through XPS analysis. This optimized interface enables superior charge storage and transport, endowing the corresponding electrode with a specific capacitance of 40.28 mF·cm⁻² at 100 mV·s⁻¹—3.2 times greater than that of conventional silver-based electrodes—along with a reduced sheet resistance. When integrated with a Nafion ion–gel membrane, the PANI@MWCNT electrode achieves a 67% increase in force density and a larger displacement output compared to standard devices, directly correlated with its enhanced electrical and electrochemical properties. This work highlights the critical role of core–shell interfacial engineering in governing electromechanical performance at the electrode–gel interface and offers a practical design strategy for developing high-performance, cost-effective IPMC actuators for soft robotics, flexible electronics, and related applications. Full article

The fabrication of high-resolution and mechanically robust copper patterns remain a critical challenge in flexible electronics. Here, we present a universal metallization strategy that combines sequential two-step laser transfer, including laser-induced backward transfer and laser-induced forward transfer, with subsequent electroless copper plating. In this approach, laser-induced backward transfer first generates a transferable copper particle donor layer; subsequently, laser-induced forward transfer selectively embeds these catalytic copper particles into the surface of target substrates, constructing spatially confined activation networks while minimizing direct thermal exposure. These embedded seeds are then amplified into continuous copper conductors via electroless copper plating, achieving a high-resolution pattern (average minimum linewidth of approximately 20 μm) with robust interfacial integrity. Benefiting from laser-induced mechanical interlocking, the resulting copper patterns exhibit a low electrical resistivity of ~2.0 × 10⁻⁸ Ω·m (comparable to bulk copper) and maintain stable electromechanical performance even after 8000 bending cycles across a radius range of 3 to 6 mm. Furthermore, the fabricated versatile electrodes are successfully integrated into a triboelectric nanogenerator for tactile sensing and Morse code transmission. With its inherent substrate universality (e.g., polyimide, wood, fabric, and paper) and process scalability, this strategy provides a versatile route for manufacturing reliable copper electrodes in next-generation flexible electronic systems. Full article

Flexible electrode materials with tailored electrical and mechanical properties are essential for reliable electrocardiographic (ECG) sensing. In this work, p-toluenesulfonic-acid-doped polypyrrole (PPy–TSA) films were modified using polymeric and inorganic fillers, as well as their combinations (polyethylene glycol, graphene, carbon nanotubes, and zeolite), to tune their functional performance. The reference PPy–TSA film exhibits typical morphological and chemical characteristics of doped polypyrrole and serves as a reliable baseline for comparison. All composite films retain electrical conductivity within the range required for ECG applications while showing improved mechanical compliance (i.e., enhanced ability to conform to the skin and sustain deformation). Based on the optimized balance between electrical and mechanical properties, flexible ECG electrodes were fabricated using the TSA-doped PPy-based composite film. ECG recordings obtained with the several proposed electrodes show good agreement with those acquired using a commercial ECG electrode, demonstrating the potential of PPy-based composite films for flexible bioelectronic sensing applications. Full article

Blended nanocomposite solid polymer electrolytes are gaining considerable attention as next-generation materials for use in flexible lithium-ion battery systems. These materials help ensure a more uniform distribution of lithium ions at the electrode–electrolyte interface, contributing to the development of a stable interfacial layer that mitigates lithium dendrite formation. In this study, solid polymer electrolytes were synthesized using a binary polymer matrix composed of polyethylene oxide (PEO) and polymethyl methacrylate (PMMA), with lithium iodide (LiI) as the ionic salt. Zirconium dioxide (ZrO₂) nanoparticles were introduced as nanofillers in varying concentrations to investigate their influence on the physical and functional characteristics of the polymer matrix. Characterization was carried out using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). SEM images indicated that ZrO₂ nanoparticles remained well-dispersed up to 3 wt%, while higher loadings showed slight agglomeration. FTIR analysis revealed noticeable changes in absorption bands, suggesting strong interactions among polymer chains and the nanofillers. XRD data confirmed the semi-crystalline behavior of the PEO/PMMA blend system. The inclusion of ZrO₂ nanofillers enhanced the structural integrity and ionic conductivity of the polymer matrix, making them promising candidates for applications in electrochemical energy storage and advanced material interfaces. The systematic incorporation of ZrO₂ nanofillers into the PEO/PMMA matrix significantly improved the microstructural uniformity, polymer–filler interactions, and ionic transport behavior of the solid polymer electrolytes. Full article

Transcutaneous electrical nerve stimulation (TENS) is constrained by high skin impedance and unstable electrode contact. This study proposes a novel composite electrode system comprising a polyvinyl alcohol/silver (PVA/Ag) microneedle array and a highly conductive polyacrylamide/lithium chloride (PAAm/LiCl) hydrogel. The PVA/Ag microneedles (~365 µm in height, ~48 µm tip diameter) possess sufficient mechanical strength to penetrate the stratum corneum, establishing a low-resistance pathway. The complementary PAAm/LiCl hydrogel exhibits high conductivity (10.28 S/m) and mechanical flexibility, further optimizing the interface contact. The experimental results demonstrate that this composite system achieves low electrochemical impedance and induces stable, clear electromyographic responses in vivo. It effectively addresses the common issues of electrode detachment and signal attenuation associated with conventional electrodes, offering a promising hardware solution for efficient and comfortable wearable rehabilitation devices. Full article