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For the first time, the ionic polymer metal composite (IPMC) actuator is integrated with a RFID (Radio-Frequency Identification) tag antenna for achieving frequency reconfiguration in the UHF (Ultra-High-Frequency) band. Here, the IPMC movable flap serves as an actuator that can effectively tune the tag resonant frequency. By applying a 2-layer crenellated structure and employing a surface patterned electrode for restraining back relaxation, the deflection of the IPMC actuator can be significantly improved. The IPMC actuator can move in two directions, enabling two-degree frequency tuning. Numerical and experimental data confirm that the tip displacement of the IPMC actuator can be enhanced up to 266% with the use of the 2-layer crenellated structure. The IPMC actuator allows the resonant frequency of the tag antenna to be tuned back by as much as 35 MHz, after deviating due to placing on an unintended object. UHF RFID application is also performed using a portable commercial RFID reader. Good frequency reconfiguration and broad tuning range, along with far read distances, have been achieved with our tunable UHF RFID tag antenna.

Cell membranes are integral to the functioning of the cell and are therefore key to drive fundamental understanding of biological processes for downstream applications. Here, we review the current state-of-the-art with respect to biomembrane systems and electronic substrates, with a view of how the field has evolved towards creating biomimetic conditions and improving detection sensitivity. Of particular interest are conducting polymers, a class of electroactive polymers, which have the potential to create the next step-change for bioelectronics devices. Lastly, we discuss the impact these types of devices could have for biomedical applications.

Dielectric elastomers (DEs) are electroactive polymers that could be used as soft actuators, stretchable generators and sensors. Their performance is dependent on both their mechanical and dielectric properties. Particularly, the dielectric constant has been shown to be dependent on the state of mechanical stretch, which has to be comprehensively characterized across different modes of deformation and different classes of DEs. We conduct experiments to characterize the stretch-dependence of dielectric constant for three classes of elastomers: acrylic (VHB), silicone and natural rubber. In our characterization, we selected three distinct modes of mechanical deformation: equal-biaxial, unequal-biaxial and uniaxial. We reviewed the five most common stretch-dependent dielectric constant models and evaluated their fit with our experimental data which were based upon stretch-dependent dielectric constant of elastomers. Comparing all the model fittings, we find that, although the polarization-based lumped parameter model presents the best fit, both localized dipole relaxation and long chain polymer polarization were absent in the model. In view of the statistical long-chain dynamics in elastomers, we therefore propose a generic, semi-empirical inverse power-law relationship to generalize and standardize the characterization of stretch-dependence of dielectric constant along with log–log curve fitting. We hope to establish a consistent and general framework for dielectric characterization of dielectric elastomers.

In this paper, intelligent materials for flexible actuators are reviewed, including fiber knitted fabric, elastic polymer, electroactive polymer, shape memory alloy and shape memory polymer. This paper will discuss the current challenges in the development of flexible actuators, and analyze its future development.

Electroactive polymers (EAPs) are an advanced family of polymers that change their shape through electric stimulation and have been a point of interest since their inception. This unique functionality has helped EAPs to contribute to versatile fields, such as electrical, biomedical, and robotics, to name a few. Ionic EAPs have a significant advantage over electronic EAPs. For example, Ionic EAPs require a lower voltage to activate than electronic EAPs. On the other hand, electronic EAPs could generate a relatively larger actuation force. Therefore, efforts have been focused on improving both kinds to achieve superior properties. In this review, the synthesis routes of different EAP-based actuators and their properties are discussed. Moreover, their mechanical interactions have been investigated from a tribological perspective as all these EAPs undergo surface interactions. Such interactions could reduce their useful life and need significant research attention for enhancing their life. Recent advancements and numerous applications of EAPs in various sectors are also discussed in this review.

Dielectric Elastomers are special electroactive polymers capable of changing their shape under electrical stimulation. These are useful lightweight materials with tremendous potential to implement ...

p-Type electroactive polymers are promising cathodes for dual-ion batteries but cost-effective candidates are still lacking. In this study, the p-type polymer polyphenothiazine (PPTZ) is synthesized by a facile one-step oxidation polymerization from the low-cost phenothiazine (PTZ) monomer. As a cathode for rechargeable lithium batteries, PPTZ shows superior electrochemical performance to previously reported PTZ-based polymers with complicated structures and syntheses. For example, PPTZ has a high reversible capacity of 157 mAh g-1 within 2.5-4.3 V vs. Li+ /Li with an average discharge voltage of 3.5 V, and a high capacity retention of 77 % after 500 cycles. The highly reversible one-electron redox mechanism of PPTZ is also investigated in detail by electrochemical testing, ex situ FT-IR and X-ray photoelectron spectroscopy, and DFT calculations. PPTZ has the potential to serve as an attractive p-type cathode material for practical applications and the facile synthesis may be also extended to other polymer cathodes based on N-heteroaromatic units.

Smart materials are a group of materials that exhibit the ability to change their composition or structure, their electrical and/or mechanical properties, or even their functions in response to an external stimulus such as heat, light, electricity, pressure, etc. Some of the advantages of these materials are: lightweight, flexibility, low cost of production, high energy density, fast response and compact size. One of the promises in the area of smart materials can be found in “smart polymer”. Polymers have many attractive characteristics, such as: lightweight, inexpensiveness, fractures tolerant, and pliable. Furthermore, they can be configured into almost any conceivable shape and their properties can be tailored according to the required needs. The capability of electroactive polymers (EAPs) to respond to electrical stimuli with a mechanical response, is attracting the attention of the scientific community from a wide range of disciplines. Biopolymers in recent decades have been studied as potential electroactive materials. These groups of polymers are extracted from a natural source; thus, they are eco-friendly, additionally they stand as a cheaper solution for the development of smart materials.The present manuscript will explore some of its applications as EAPs.

Different types of active materials have been used to actuate origami-inspired self-folding structures. To model the highly nonlinear deformation and material responses, as well as the coupled field equations and boundary conditions of such structures, high-fidelity models such as finite element (FE) models are needed but usually computationally expensive, which makes optimization intractable. In this paper, a computationally efficient two-stage optimization framework is developed as a systematic method for the multi-objective designs of such multifield self-folding structures where the deformations are concentrated in crease-like areas, active and passive materials are assumed to behave linearly, and low- and high-fidelity models of the structures can be developed. In Stage 1, low-fidelity models are used to determine the topology of the structure. At the end of Stage 1, a distance measure [Formula: see text] is applied as the metric to determine the best design, which then serves as the baseline design in Stage 2. In Stage 2, designs are further optimized from the baseline design with greatly reduced computing time compared to a full FEA-based topology optimization. The design framework is first described in a general formulation. To demonstrate its efficacy, this framework is implemented in two case studies, namely, a three-finger soft gripper actuated using a PVDF-based terpolymer, and a 3D multifield example actuated using both the terpolymer and a magneto-active elastomer, where the key steps are elaborated in detail, including the variable filter, metrics to select the best design, determination of design domains, and material conversion methods from low- to high-fidelity models. In this paper, analytical models and rigid body dynamic models are developed as the low-fidelity models for the terpolymer- and MAE-based actuations, respectively, and the FE model of the MAE-based actuation is generalized from previous work. Additional generalizable techniques to further reduce the computational cost are elaborated. As a result, designs with better overall performance than the baseline design were achieved at the end of Stage 2 with computing times of 15 days for the gripper and 9 days for the multifield example, which would rather be over 3 and 2 months for full FEA-based optimizations, respectively. Tradeoffs between the competing design objectives were achieved. In both case studies, the efficacy and computational efficiency of the two-stage optimization framework are successfully demonstrated.

Plasticized polyvinyl chloride (PVC) gel is a type of electroactive polymers, which has potentials to be applied as soft actuators. However, few studies have been performed to investigate the mechanical responses of PVC gels in cyclic loading conditions. In this work, we combined experiments and theory to characterize the mechanical responses of two plasticized PVC gels. The gels were subjected to different types of loading-unloading-reloading cycles. The experimental results showed that the plasticized PVC gels exhibited stress softening response (the Mullins effect) in the cyclic tests. Meanwhile, the gels regained some strength after annealing at room temperature for several hours, indicating the self-healing ability of gels. We further extended the eight-chain model with incorporation of the chain dissociation and reassociation mechanism. The developed constitutive model is able to reproduce the Mullins effect and the recovery of the Mullins effect observed in the experiments. Our results clearly show that understanding the complex mechanical response is crucial for the applications of plasticized PVC gels.

The development of small-molecule acceptors (SMAs) has significantly enhanced the power conversion efficiency (PCE) of polymer solar cells (PSCs); however, the inferior mechanical properties of SMA-based PSCs often limit their long-term stability and application in wearable power generators. Herein, we demonstrate a simple and effective strategy for enhancing the mechanical robustness and PCE of PSCs by incorporating a high-molecular-weight (MW) polymer acceptor (PA, P(NDI2OD-T2)). The addition of 10–20 wt % PA leads to a more than 4-fold increase in the mechanical ductility of the SMA-based PSCs in terms of the crack onset strain (COS). At the same time, the incorporation of PA into the active layer improves the charge transport and recombination properties, increasing the PCE of the PSC from 14.6 to 15.4%. The added PAs act as tie molecules, providing mechanical and electrical bridges between adjacent domains of SMAs. Thus, for the first time, we produce highly efficient and mechanically robust PSCs with a 15% PCE and 10% COS at the same time, thereby demonstrating their great potential as stretchable or wearable power generators. To understand the origin of the dual enhancements realized by PA, we investigate the influence of the PA content on electrical, structural, and morphological properties of the PSCs.

The usage of ionic polymer metal composite (IPMC) being an electroactive polymer is prevalent in different engineering applications. IPMC are synthetic composite nanomaterials which show artificial muscle behavior under applied voltage or electric impetus. When an electrical potential is applied across the two membranes, the positively charged conjugated and hydrated cations migrate toward the negative electrode. This migration creates an osmotic pressure gradient across the membrane; hence, the strip gets deformed or bent. On the other hand, IPMC strips are capable of generating electrical potential under the action of stretching or bending (thereby acting as a sensor). In this letter, the authors report the pragmatic application of the IPMC strip to study a taste sensor. The sensing characteristics of IPMC strips are applied to sense five general tastes (sweet, sour, bitter, salty, and spicy). Primarily, IPMCs are immersed into individual solutions and kept for 15 min for doping action. Thus, different solutions having distinct concentration of ions will lead to distinct identifications. In this present investigation, the authors have instigated the IPMC strip as a sensor; when an IPMC strip is bent or deformed, an analogous voltage in the range of millivolts is generated across the membranes. Second, clammy IPMCs are bent in the clockwise and again in the counterclockwise direction (10°) to record the corresponding voltage. A set of experimental data was collected, which divulged unique characteristics for different solutions pertinent to different tastes. Thus, IPMC strips are able to recognize different taste senses.

In this paper, the primary purpose is to have a complete understanding of the importance of fibers in dielectric elastomers due to the influence of fiber orientation in decreasing the applied voltage to simulate the structure and improving mechanical performance. Fibers will also reduce the chance of failure like Wrinkling instabilities and increase the response rate under electric displacement. Implementing the dielectric elastomers with anisotropic structure, despite their great potential, has not adequately analyzed in previous researches. Therefore, based on nonlinear continuum mechanics and large inelastic deformations, the constitutive relationships and equations governing the behavior of viscoelastic dielectric elastomers under harmonic electrical loading are extracted and analyzed in different states. The numerical results, such as phase and frequency-amplitude diagrams and the oscillation, illustrate the dynamic behavior of an anisotropic dielectric elastomer with different fiber orientations. To describe the viscoelasticity behavior of the material, hyperelastic models and the rheological model, are used in conjunction with electrical coupling. Using the theory of anisotropic dielectric elastomers, a geometrically nonlinear formulation under finite deformations is developed by the Euler-Lagrange equations and solved mathematically.

While the fascinating field of soft machines has grown rapidly over the last two decades, the materials they are constructed from have remained largely unchanged during this time. Parallel activities have led to significant advances in the field of dynamic polymer networks, leading to the design of three‐dimensionally cross‐linked polymeric materials that are able to adapt and transform through stimuli‐induced bond exchange. Recent work has begun to merge these two fields of research by incorporating the stimuli‐responsive properties of dynamic polymer networks into soft machine components. These include dielectric elastomers, stretchable electrodes, nanogenerators, and energy storage devices. In this Minireview, we outline recent progress made in this emerging research area and discuss future directions for the field., Polymer networks cross‐linked through bonds capable of exchanging with one another have a high potential for increasing the sustainability of polymeric materials. However, the adaptive and responsive properties of these networks can also enhance the properties of electroactive polymers in smart and functional devices. This Minireview highlights recent work at this emerging research boundary and discusses future directions for dynamic polymer networks in soft machine applications.

Electroconductive hydrogels (EHs) are promising composite biomaterials of hydrogels and conductive electroactive polymers, incorporating bionic physicochemical properties of hydrogels and conductivity, electrochemistry, and electrical stimulation (ES) responsiveness of conductive electroactive polymers. The biomedical domain has increasingly seen EHs’ application to imitating the biological and electrical properties of human tissues, acclaimed as one of the most effective biomaterials. Bone’s complex bioelectrochemical properties and the corresponding stem cell differentiation affected by electrical signal elevate EHs’ application value in repairing and treating bone, cartilage, and skeletal muscle. Noteworthily, the latest orthopedic biological applications require broader information of EHs. Except for presenting the classification and synthesis of EHs, this review recapitulates the advance of EHs application to orthopedics in the past five years and discusses the pertinent development tendency and challenge, aiming to provide a reference for EHs application direction and prospect in orthopedic therapy.

The deterioration of organic film due to chemical and UV attack is an increasing concern in paint technology. Thus, the development of new material for UV blocking anticorrosive film draws significant attention in materials science research. This can be achieved by the incorporation of wide band gap nanoparticles like titania (TiO2NPs) and zirconia (ZrO2NPs) in electroactive polymer namely poly(pyridine-4-yl-methyl) methacrylate-co-butyl methacrylate (poly(PyMMA-co-BMA)) film (hybrid film) for the protection of mild steel (MS) from corrosion. The TiO2NPs and ZrO2NPs in combination with polymer absorb more UV light which prevents the deterioration of film. The hybrid material made of poly(PyMMA-co-BMA) and wide band gap nanoparticles was prepared by in situ solution polymerization. The resultant hybrid materials were characterized by various techniques namely X-ray diffraction studies (XRD) and transmission electron microscopy (TEM). The hybrid materials were deposited as film on the MS by spin coating method. The anticorrosive performance of hybrid films was analysed out using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies. The surface examination of films were characterized with scanning electron microscope to confirm the formation of poly(PyMMA-co-BMA) and its different nanocomposite films on MS. The UV blocking studies were also carried out using UV-visible spectroscopy. The electrochemical and optical studies reveals that the poly(PyMMA-co-BMA)/TiO2 film on MS in 3.5% (w/v) NaCl provides better protection against corrosion than ZrO2 based nanocomposite hybrid film.

Microsphere based consecutive model is useful tool to predict the material behavior of dielectric elastomer composite containing directionally arranged soft fillers. Dielectric elastomers (DEs) belong to electroactive polymers (EAPs) family, which produce mechanical deformation in response to change in external electrical potential and vice-versa. Some tunable properties like softness, flexibility, light weight etc. makes DE suitable candidate for electromechanical transducers (actuator, sensor and energy harvester). With the increase in relative permittivity, strain energy also increases thus the performance of electromechanical transducer. Material modification, chemical blending, and composite with nanoparticles act as a tool to enhance the relative permittivity. Particle filled composite of elastomer is appeared to be noticeable due to the easiness and flexibility of the method. However recent studies show that electrically cured DE composite (DEC) forms chain-like structure and generate anisotropy in the composite material. Also, manufacturing condition and undesired properties of filler introduce anisotropy to the composite. In present line of work, precise and accurate steps were taken to investigate the effect of amount of soft fillers on the anisotropic behavior in DE composite. Analytical result shows the similar pattern of pressure variation DE composite based cylindrical actuator with enhanced pressure. The possible reason for the enhanced pressure variation with strain may be softening of host elastomer due to addition of filler particle as well as the increase in the load. The results may help the researcher to manufacture soft, flexible and improved DE composite for energy harvester application.

Electroactive polymers based on dielectric elastomers are stretchable and compressible capacitors that can act as transducers between electrical and mechanical energies. Depending on the targeted application, soft actuators, sensors or mechanical-energy harvesters can be developed. Compared with conventional technologies, they present a promising combination of properties such as being soft, silent, light and miniaturizable. Most of the research on dielectric elastomer actuators has focused on obtaining the highest strain, either from technological solutions using commercially available materials or through the development of new materials. It is commonly accepted that a high electrical breakdown field, a low Young's modulus and a high dielectric constant are targets. However, the interdependency of these properties makes the evaluation and comparison of these materials complex. In addition, dielectric elastomers can suffer from electromechanical instability, which amplifies their complexity. The scope of this review is to tackle these difficulties. Thus, first, two physical parameters are introduced, one related to the energy converted by the dielectric elastomer and another to its electromechanical stability. These numbers are then used to compare dielectric elastomers according to a general and rational methodology considering their physicochemical and electromechanical properties. Based on this methodology, different families of commercially available dielectric elastomers are first analyzed. Then, different polymer modification methods are presented, and the resulting modified elastomers are screened. Finally, we conclude on the trends enabling the choice of the most suitable modification procedure to obtain the desired elastomer. From this review work, we would like to contribute to affording a quick identification method, including a graphic representation, to evaluate and develop the dielectric materials that are suitable for a desired actuator.

Sample library preparation is a central step in the process of evaluating materials with the general aim of efficient library formulation while minimizing resource consumption. We demonstrate here the first implementation of a microfluidic-enabled thin film sample library formulation platform with integrated inkjet printing capability for directly patterning these libraries with reduced material wastage. System development and general performance screening protocol for these patterned thin films are described. We study the combinatorial formulation capabilities of this system by focusing on some practical case studies for probing the electrical conductivity in organic, biocompatible and electroactive polymer/additive (PEDOT:PSS/DMSO and PEDOT:PSS/EG) blends. Functionally-graded thin film libraries are prepared by mixing ink components and directly dispensing the processed blends into programmed geometries using the integrated platform. Electrical and morphological characterization of these printed thin film libraries is conducted to validate the formulation efficacy of the platform. Interrogating these printed libraries, we were able to iteratively identify the location of conductivity maxima for the studied blends and corroborate the morphological basis of this enhancement with established theories.

Poly(vinylidene fluoride) (PVDF) and its random copolymers exhibit the most distinctive ferroelectric properties; however, their spontaneous polarization (60–105 mC m−2) is still inferior to those (>200 mC m−2) of the ceramic counterparts. In this work, we report an unprecedented spontaneous polarization (Ps = 140 mC m−2) for a highly poled biaxially oriented PVDF (BOPVDF) film, which contains a pure β crystalline phase. Given the crystallinity of ∼0.52, the Ps for the β phase (Ps,β) is calculated to be 279 mC m−2, if a simple two-phase model of semicrystalline polymers is assumed. This high Ps,β is invalid, because the theoretical limit of Ps,β is 185 mC m−2, as calculated by density functional theory. To explain such a high Ps for the poled BOPVDF, a third component in the amorphous phase must participate in the ferroelectric switching to contribute to the Ps. Namely, an oriented amorphous fraction (OAF) links the lamellar crystal and the mobile amorphous fraction. From the hysteresis loop study, the OAF content was determined to be ∼0.28, more than 50% of the amorphous phase. Because of the high polarizability of the OAFs, the dielectric constant of the poled BOPVDF reached nearly twice the value of conventional PVDF. The fundamental knowledge obtained from this study will provide a solid foundation for the future development of PVDF-based high performance electroactive polymers for wearable electronics and soft robotic applications.

3D porous polymeric materials have a wide range of applications and can be obtained from different approaches as passive materials, permanently set after fabrication. Stimuli-responsive materials give the opportunity to implement a 4th dimension to these materials, providing dynamic characteristics due to the changes in their shape, morphology, pore size or mechanical properties under external stimulation. In this work, the functionalization of 3D scaffolds with an electroactive polymer, the poly(3,4-ethylenedioxthiophene) (PEDOT), has been explored. This conductive polymer which is responsive to electrical stimulation appears as a convenient trigger for several applications, due to its ease of integration and control and its biocompatibility. 3D porous materials based on polymerized high internal phase emulsion (polyHIPE) have been successfully prepared through emulsion templating, leading to materials with highly interconnected and open porosity. The polyHIPE composition is chosen to provide soft and compliant scaffolds, compatible with the functionalization, electrochemical stimulation and electromechanical deformation of PEDOT. The polyHIPE walls are then functionalized homogeneously with PEDOT without any pore obstruction, conferring excellent electrical and electromechanical properties to the porous material. The resulting 4D smart electroactive polyHIPE demonstrates a porosity variation of 10% in the PBS electrolyte under an electrical stimulation of ±0.8 V. These 4D PolyHIPE/PEDOT electroactive scaffolds pave the way for the development of smart and multifunctional 4D materials for numerous applications, especially in the fields of biomedical devices and cell culture platforms.

Detection of biomarkers at the cellular level can provide more accurate and comprehensive information that is important for early diagnosis of diseases and evaluation of new drugs. However, the interference of a large number of components in cells and the requirement of high sensitivity bring great challenges for their detection. Herein, a robust and enzyme-free electrochemical platform was proposed for microRNA-21 (miRNA-21) detection by integrating the efficient separation of magnetic nanobeads (MBs) with the multisignal amplification of strand displacement amplification (SDA) and electrochemically mediated atom transfer radical polymerization (eATRP). The eATRP is capable of de novo growth of a number of electroactive polymers on the electrode surface for signal amplification. Compared to simple hybridization, SDA and eATRP can enhance the signals by ∼35-fold, achieving high signal-to-noise ratio for low-abundant target detection. Owing to their superparamagnetism and strong magnetic response ability, MBs endow the method with excellent specificity and anti-interference ability to detect miRNA-21 in cells. Using MBs as capture carriers, SDA and eATRP for signal amplification, and gold nanoflower (AuNF)-modified electrodes as working electrodes, as low as 0.32 aM miRNA-21 was detected. Furthermore, the successful detection of miRNA-21 in cells indicated the great prospect of this method in the early diagnosis of cancers, life science research, and single-entity electrochemical detection.

This paper presents dielectric elastomer actuated robot locomotion and the development of a robotic model structure based using a dielectric elastomer actuator. A pre-stretched dielectric elastomer actuator is fabricated onto acrylic frames to form single and multiple robotic crawler models. The crawler models demonstrate forwards motion upon application of high voltage to the attached dielectric elastomer actuator. Characterizations revealed that the fabricated multiple crawler models showed results over the single crawler model in terms of locomotion potential. The maximum forward locomotion speed of the multiple crawler models is recorded as 1.2 mm/s. Nonetheless, precise results are highly attainable provided a structured and coherent fabrication technique of the dielectric elastomer actuator is implemented.

The accurate modeling of electrical impedance over a wide range of frequency is essential for precise dynamic modeling and control problems of Electroactive Polymer (EAP) actuators. Recently, fractional order modeling has attracted more attention due to the high accuracy. This paper deals with a fractional order electrical impedance model and its identification procedure for a class of EAP actuator named Ionic Polymer Metal Composite (IPMC). To take IPMC’s fractional characteristic into account, constant phase element (CPE) is used to construct a model structure according to Electrochemical Impedance Spectroscopy (EIS). By employing the Levy’s method in combination with genetic optimization algorithm, the unknown parameters of the resulting fractional transfer function are identified. Finally the proposed model is verified, by comparing with experimental EIS data. The results show that the fractional order model has high accuracy for representing the electrical impedance of IPMC actuator. The proposed modeling procedure is general and can also be used for any type of EAPs.

Advances in the field of new smart materials suggested investigating their capabilities as energy harvesters. Ionic polymer-metal composite (IPMC) is a relatively new type of smart materials and it belongs to the class of electroactive polymers (EAP). IPMC has already been considered as a potential candidate for energy harvester by several researchers. In this paper, a tapered (in thickness) IPMC energy harvester is considered to investigate the effects of modification of geometric configurations on energy harvesting capabilities. A mathematical model for the tapered IPMC harvester is developed. The energy harvester is analyzed using the proposed mathematical model. Numerical results show that the present harvester configuration can generate a significant amount of power. Moreover, the tapered IPMC energy harvester improves the fatigue life of the harvester as the tapered geometry reduces stress concentration at the fixed point. Therefore, the tapered IPMC energy harvester can be considered for several engineering applications such as wearable sensors, micro-electro-mechanical devices, etc.

Electroactive polymer (EAP) is a kind of smart material, which can change its shape under the stimulation of electric field. Dielectric elastomer (DE) is an important member of the EAP. DE has the characteristics of excellent performance, such as light weight, low noise, low cost, and so on, which guarantee its wide applications in the fields of actuators, generators, sensors. In this review, the principles of energy conversion, the research status and latest development of new technologies for DEs, and the performance characteristics of DEs are summarised. Simultaneously, it points out the development problems and feasible countermeasures. At last, the application prospects of DE are discussed, combined with the research direction of the international frontier.

Multifunctional materials with sensor and actuator capabilities are playing an increasing role in modern technology. In this scope, hybrid materials with magnetic sensing and electromechanical actuator response based on magnetic ionic liquids (MILs) and the polymer poly(vinylidene fluoride) (PVDF) have been developed. MILs comprising different cation alkyl chain lengths [Cnmim]+ and sharing the same anion [FeCl4] - were incorporated at 20% wt. into the PVDF matrix and the morphological, physical-chemical and functional properties of the materials evaluated. Increasing IL alkyl chain length leads to the formation a porous structure , together with an increase in the electroactive PVDF β phase content of the polymer and a decreasing in the crystallinity degree and the thermal stability. The magnetic susceptibility of the [Cnmim][FeCl4] - /PVDF films reveals a paramagnetic behavior. The multifunctional response is characterized by a magnetoionic response that decreases with increasing IL alkyl chain length, being the highest magnetoionic coefficient (1.06±0.015 V cm1 Oe-1 ) observed for [C2mim][FeCl4]/PVDF. The electromechanical actuator response is characterized by a highest displacement of 2.2 mm for the [C4mim][FeCl4]/PVDF film by applying a voltage of 4 V at a frequency of 100 mHz. Further, their solution processing makes those multiresponsive materials compatible with additive manufacturing technologies., Funding from the FCT - Fundação para a Ciência e Tecnologia: Strategic Funding UID/FIS/04650/2020 and UIDB/50006/2020, projects PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017 and grants SFRH/BD/145345/2019 (LCF) and SFRH/BPD/121526/2016 (DMC). Funding from the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD): PID2019-106099RB-C43 / AEI /10.13039/501100011033. Funding from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively. Technical and human support from SGIker (UPV/EHU, MICINN, GV/EJ, EGEF and ESF) is gratefully acknowledged.

Living tissues in the body receive various types of stimuli, including mechanical strain, pressure, and varied chemical environments. In contrast, conventional cell cultures are processed under in vitro conditions, which are not similar to the actual body’s environment. To precisely simulate the human body environment, a dynamic cell culture device capable of applying mechanical stimulation to cells is needed. In this study, an acrylic dielectric elastomer electroactive polymer (EAP), is introduced as a driving component for a dynamic cell culture device with a simple structure. The device is composed of separated upper and lower modules with a driving film at the center, By assembling these components, the electrodes on the surface of the driving film are isolated but still connected by columns that can transfer the deformation of the driving apparatus to the culture membrane. The culturing performance of cells according to the mechanical stimuli was experimentally investigated and compared. Tensile strain was found to provide the highest improvement in cell development rate, reaching up to 32.3%. These results highlight the utility of EAPs for compact and biocompatible dynamic cell culture device design.

Operation features of actuators based on the domestic electroactive polymer MF-4SK in combination with graphene electrodes is first studied. This system demonstrates several advantages, e.g. better mutual adhesion of materials, over those employing conventional flexible metal electrodes and Nafion membranes. The reported model of electroactive polymers connects sizes and structure of water-filled pores to geometrical characteristics of polymers with the goal of comparing properties of MF-4SK and Nafion polymers.

Dielectric elastomeric materials are a new type of electroactive polymers that can produce large deformation under electric field stimulation and can be widely used as actuators and sensors. Among them, Dow Corning’s PDMS is the most widely studied silicone rubber-based dielectric elastomer material. Its key electrical parameters, especially the dielectric constant, affect the overall electromechanical coupling performance. So far, people’s understanding of the dielectric constant value of PDMS dielectric materials is not uniform, especially the influence of frequency on dielectric constant is very different, and few scholars analyze it from the mechanism. Based on this situation, different TiO2/PDMS dielectric elastomers were prepared firstly, and then the influence of frequency (0–105 Hz) on the dielectric properties of TiO2/PDMS dielectric materials was studied by high–low-frequency dielectric constant meter. It is found that the material has strong low frequency dependence and weak high frequency dependence. Finally, from the microscopic point of view, the mechanism of the dielectric constant of TiO2/PDMS dielectric material changing with frequency is due to the fact that material dipole steering polarizability changes with frequency.

Ionic polymer-metal composite (IPMC) actuators are one of the most prominent electroactive polymers with expected widespread use in the future. The IPMC bends in response to a small applied electric field as a result of the mobility of cations in the polymer network. This paper proposes a Levenberg-Marquardt algorithm backpropagation neural network (LMA-BPNN) prediction model applicable for Cu/Nafion-based ionic polymer-metal composites to predict the actuation property. The proposed approach takes the dimension ratio (DR) and stimulation voltage as the input layer, displacement and blocking force as the output layer, and trains the LMA-BPNN with the experimental data so as to obtain a mapping relationship between the input and the output and obtain the predicted values of displacement and blocking force. An IPMC actuating system is set up to generate a collection of the IPMC actuating data. Based on the input/output training data, the most suitable structure was found out for the BPNN model to represent the IPMC actuation behavior. After training and verification, a 2-9-3-1 BPNN structure for displacement and a 2-9-4-1 BPNN structure for blocking force indicate that the structure can provide a good reference value for the IPMC. The results showed that the BPNN model based on the LMA could predict the displacement and blocking force of the IPMC. Therefore, this model can become an effective solution for IPMC control applications.

International audience; A polyvinylidene fluoride (PVDF)/hydrogenated nitrile rubber (HNBR)-based flexible electroactive polymer blend was developed by generating a suitable morphology that showed a judicious combination of strength and flexibility. The blend, containing 30:70 wt/wt ratio of PVDF/HNBR, was thermoplastic elastomeric in nature and exhibited visible planar actuation in the presence of an electric field. To the best of our knowledge, the electromechanical actuation of the thermoplastic elastomeric blend has been reported for the first time. The maximum planar strain was 5%, and the actuation was triggered by the strong induced polarization in both PVDF and HNBR phases that gave rise to a high dielectric constant and low dielectric losses. The interphase between PVDF and HNBR was also very strong, which made the thermoplastic elastomer (TPE) susceptible to withstand high electric field. The TPE also exhibited a bending actuation of 0.6 mm at a low electric field of 20 kV/mm, promising enough to be used in microdevices. Addition of barium titanate (BT) nanoparticles increased the dielectric constant as they were homogeneously distributed in both the phases. The maximum planar actuation (∼10%) was observed at 10 wt % BT loading, whereas 5 wt % loading exhibited the maximum dielectric strength (∼120 kV/mm). At 5 wt % loading, the bending actuation was 0.9 mm at 20 kV/mm, which was 50% higher than that of unfilled TPE. Both the TPE and its nanocomposite also showed good history dependency in a cyclic electric field. In summary, the study provides an attractive and unexplored alternative of developing electromechanically active TPEs and their nanocomposites.

Ionic electroactive polymer (iEAP) actuators have attracted wide attention due to their capability of producing desired deformation under low voltages by ion diffusion. However, these actuators are always subjected to a slow response and fatal delamination at the bonding interface during deformation. Here, we report a novel polyimide/gold/bismuth (PI/Au/Bi) actuator driven by the electrochemical redox of PI with tunable active/passive layer thickness to generate large and tunable strain, where metallic Bi is indispensable to promote the actuating behavior by enhancing the reversible redox of PI. Much faster charge transportation and better conductivity of the PI/Au/Bi film were observed after coating with Bi. The actuator demonstrated large and tunable strain under a long service life owing to the fact that PI acted as both the active layer and passive layer, which effectively ruled out the delamination issue. This work not only develops bismuth-enhanced ionic actuators, but finds a new use for low-dielectric-constant polymers rather than conductive polymers as actuator materials.

This study presents a transparent and soft haptic actuator based on an electroactive polymer designed to create abundant haptic sensations in flexible/deformable next-generation devices and to convey them to users. The haptic sensations are created in the form of vibrations and vary depending on the amplitude and frequency of the vibrations. The haptic actuator consists of a transparent and soft dielectric layer and two transparent and soft ionic conductive layers. The dielectric layer is sandwiched between the two ionic conductive layers, and is compressed in the thickness direction when an electric field is applied to the two ionic conductive layers. When the applied electric field is removed, the proposed haptic actuators are rapidly restored to their initial configuration. Owing to this effect, the actuator can easily create vibrations that are sufficiently strong for human perception. In this study, three different dielectric elastomers (silicone rubber, poly urethane, and acrylic polymer) are used for the dielectric layer. Experiments are conducted to investigate the haptic performance of the proposed soft vibrotactile actuators using an accelerometer. In the case of the silicone rubber-based actuator, the measured acceleration at the resonant frequency (80 Hz) is 1.408 g (g = 9.8m/s2) and the response time is approximately 2.8 ms. Furthermore, the perceived intensity of the stimuli generated by the proposed actuator is verified by perceptual experiments. The results indicate that the proposed actuator can selectively stimulate human mechanoreceptors with sufficient perceptual strength.

4D printing is proposed based on the additive manufacturing of stimuli-responsive materials and structures, which can realize shape changing upon external stimuli. This article reviews the 4D printing methods and actuating performances of 4D printing structures based on shape memory polymers, hydrogels, liquid crystal elastomers, and electroactive polymers. This article shows that the shape morphing properties of single materials are limited, while 4D printing of composites can integrate the various driving modes of different smart materials. In the end, challenges facing 4D printing such as broadening the scope of smart materials, improving printing processes, the compatibility of printing different materials have been discussed.

With increasing energy demands associated with portable electronics, routes to capture dissipated energy associated with everyday actions (energy harvesting) can be a key component in an integrated...

Novel microfluidic substrates based on electrospun poly(l-lactic acid) (PLLA) membranes were developed to increase the limited range of commercially available paper substrates, commonly used for the fabrication of microfluidic paper-based analytical devices. PLLA’s advantageous properties include biodegradability, biocompatibility, ease of being processed in various tailored morphologies, and cost effectiveness, among others. Oriented and nonoriented electrospun PLLA membranes were fabricated using electrospinning and the influence of fiber orientation, addition of hydrophilic additives, and plasma treatments on the morphology, physicochemical properties, and capillary flow rates were evaluated and compared with the commercial Whatman paper. In addition, a proof-of-concept application based on the colorimetric detection of glucose in printed PLLA and paper-based microfluidic systems was also performed. The results show the potential of PLLA substrates for the fabrication of portable, disposable, eco-friendly, and cost-effective microfluidic systems with controllable properties that can be tailored according to specific biotechnological application requirements, being a suitable alternative to conventional paper-based substrates., This work was supported by the Portuguese Foundation for Science and Technology (FCT) under strategic funding UID/EEA/04436/2019 and UID/FIS/04650/2019 and projects POCI-01-0145-FEDER-028159 and POCI-01-0145-FEDER-028237. Funds provided by FCT in the framework of EuroNanoMed 2016 call, Project LungCheck ENMed/0049/2016 are also gratefully acknowledged. The authors also thank the FCT for financial support under grants SFRH/BD/140698/2018 (R.B.P.) and SFRH/BD/141136/2018 (T.M.A.) The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016- 76039-C4-3-R (AEI/FEDER, UE). Financial support from the Basque Government Industry and Education Departments under ELKARTEK, HAZITEK and PIBA (PIBA2018-06) programs, respectively, is also acknowledgeds.

Understanding the role of interface properties is crucial in the search for alternative design strategies to optimize the efficiency, performance, and lifetime of both solid-state and redox active organic semiconductor devices. Recent advances have focused on controlling and tailoring interfacial effects on the morphology and molecular structure of the active film in multilayer devices triggering new developments in the area of interface engineering. Here, we demonstrate that an inorganic electrode/organic semiconductor interface modification using PEDOT:PSS as an interfacial material influences the charge and ion transport, capacitive, morphological, and color switching properties of a solution processed purple-to-clear switching electrochromic PProDOT-(CH

Flexible polymer-based actuators, often also called artificial muscles, are an essential part of biomimetic systems that mimic the movement principles of animal world creatures. The most used electrode material to force the actuator move is an ensemble of noble metal nanoparticles in the electroactive polymer surface. Noble metal electrodes have enough electrical conductivity and elasticity and are not subjected to oxidation. However, high cost of such electrodes and their tendency to cracking dictate the need for searching other materials, primarily carbon ones. The review considers several options for this search. For example, carbon nanotubes and graphene have excellent properties at the level of a single individually taken nanotube or graphene sheet. However, conservation of these properties in structurally imperfect film electrodes requires a separate study. In addition, there are problems of compatibility of such electrodes with the polymers that requires cumbersome technologies, e.g., hot pressing, which complicates the production of the actuator as a whole. The review concerns the technology options of manufacturing actuators and the results obtained on their basis, both including hot pressing and avoiding this procedure. In particular, the required level of the graphene oxide reduction in hydrazine provides sufficient adhesion at rather high electrical conductivity of the graphene film. The ability to simultaneous achieving these properties is a nontrivial result, providing the same level of actuation as with expensive noble metal electrodes. Actuators that additionally require greater lifetime resource should be obtained in other ways. Among them are using the graphdiyne electrodes and laser processing of the graphene electrodes.

A novel biosensing interface for tumor markers was designed based on the atom transfer radical polymerization (ATRP) of poly(isopropenylphenol) (PPPL) in situ initiated by the fixing of p-chloromethyl benzoic acid on the surface of amino-modified electrodes. It was found that the electrochemical activity of PPPL itself can provide sufficient signals for these biosensors, which can avoid signal leakage and streamline the interface modification process. Cu(II) ions absorbed on the carbon spheres and then were released via acid stimulation to act as a catalyst to participate in the interface polymerization with ATRP. As the concentration of targets increased, more Cu(II) ions were released, and the electrochemical signal of polymers was enhanced. Therefore, the sensitive detection of carbohydrate antigen 19-9 (CA19-9) as a model target was achieved, with an ultralow limit of detection of 39 µU mL-1 and wide detection range from 100 µU mL-1 to 100 U mL-1 under optimal conditions. Furthermore, this method achieved satisfying performance in human blood serum with good inter-assay precision (RSD

Plasticized poly (vinyl chloride) (PVC) gel is a promising electroactive polymer material for soft actuators and sensors, and it has attracted extensive attention and interest in multi-disciplinary fields. Chlorinated polyvinyl chloride (CPVC) has enhanced mechanical and chemical properties and shows a promising potential for fabricating gel materials for electroactive polymer gel actuators. Thus, we proposed a novel soft actuator based on CPVC gels. We studied the properties of CPVC gels with various technologies, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) analysis, thermogravimetric analysis (TGA), etc. Furthermore, CPVC gel actuators were fabricated and the influence of membrane thickness and plasticizer content on the basic characteristics was investigated. The experimental results show that the CPVC gel actuator with a higher content of DBA has a better strain than that of the actuator with lower amount of DBA despite the membrane thickness. With the same ratio of DBA, the CPVC gel actuator has a better performance than the traditional PVC gel actuator under a low applied load. The maximum strain and stress of the CPVC gel (CPVC : DBA = 1 : 2.5) actuator are 9% and 0.12 MPa respectively at 400 V, which reaches the same level of the PVC gel actuator with higher content of DBA (PVC : DBA = 1 : 4). These results demonstrate a good potential of the proposed CPVC gel soft actuator for practical application.

Soft robotics and wearable devices are promising technologies due to their flexibility. As human-soft robot interaction technologies advance, the interest in stretchable sensor devices has increased. Currently, the main challenge in developing stretchable sensors is preparing high-quality sensors via a simple and cost-effective method. This study introduces the do-it-yourself (DIY)-approach to fabricate a carbon nanotube (CNT) powder-based stretchable sensor. The fabrication strategy utilizes an automatic brushing machine to pattern CNT powder on the elastomer. The elastomer ingredients are optimized to increase the elastomer compatibility with the brushing method. We found that polydimethylsiloxane-polyethyleneimine (PDMS-PEIE) is 50% more stretchable and 63% stickier than previously reported PDMS 30-1. With these improved elastomer characteristics, PDMS-PEIE/multiwalled CNT (PDMS-PEIE/MWCNT-1) strain sensor can realize a gauge factor of 6.2–8.2 and a responsivity up to 25 ms. To enhance the compatibility of the powder-based stretchable sensor for a wearable device, the sensor is laminated using a thin Ecoflex membrane. Additionally, system integration of the stretchable sensors are demonstrated by embedding it into a cotton-glove and a microcontroller to control a virtual hand. This cost-effective DIY-approach are expected to greatly contribute to the development of wearable devices since the technology is simple, economical, and reliable.

[EN]Redox-active polymers have gained interest as environmentally friendly alternative to inorganic materials in applications such as electrodes in lithium-ion batteries. All-polymer batteries were first disregarded with respect to other technologies due to their lower energy densities. However, the inherent benefits of redox polymers such as processability, flexibility, recyclability, high-rate performance and the perspective to prepare batteries from renewable resources has re-ignited interest in recent years. This review article aims to provide a comprehensive overview on the state of the art of batteries in which the active material is a redox polymer; including "static" all-polymer batteries and polymer-air batteries but also "flowing" systems such as polymer based redox-flow batteries (pRFB). First, a succinct overview of the recent developments of redox polymers will be given, summarizing the historic trends and developments. Second, an exhaustive discussion of the various battery prototypes will be provided, considering all steps in the development of organic batteries just based in redox polymers. Finally, future perspectives on all-polymer batteries will be discussed, summarizing the major challenges that are still to be overcome to unlock their commercial implementation. Authors thank POLYSTORAGE ETN project, this project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant agreement No 860403. RM and NP thank the Spanish MCI through the SUSBAT project (Ref. RTI2018-101049-B-I0 0) and Juan de la Cierva fellowship [FJC2018-037781-I] (MCI-AEI/FEDER, UE) . NC would like to thank the University of the Basque Country forfunding through a specialization of research staff fellowship (ES-PDOC 19/99) . NG acknowledges the funding from the European Union's Horizon 2020 framework programme under the Marie Skodowska-Curie Agreement No. 101028682.