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Electroactivity was noticed early in biological substances, including proteins, polynucleotides and enzymes, even piezoand pyroelectricity were found in wool, hair, wood, bone and tendon. Recently, ferroelectricity has been identified in a surprisingly large number of biologically relevant materials, including hydroxyapatite, aortic walls and elastin. Inspired by the variety of natural electroactive materials, a wealth of new elastomers and polymers were designed recently, including an all organic elastomer electret and self-healing dielectric elastomers. Let’s further draw inspiration from nature and widen the utilization of electroactive polymers towards (mobile) healthcare and biomedical applications. Ferroelectrets, internally charged polymer foams with a strong piezoelectric thickness coefficient are employed in biomedical sensing, for example as blood pressure and pulse sensor, as vital signs monitor or for the detection of tonicclonic seizures. Piezo- and pyroelectric polymers are booming in printed electronics research. They provide electronic skin the ability to “feel” pressure and temperature changes, or to generate electrical energy from vibrations and motions, even from contractile and relaxation motions of the heart and lung. Dielectric elastomers are pioneered by StretchSense as wearable motion capture sensors, monitoring pressure, stretch, bend and shear, quantifying comfort in sports and healthcare. On the cellular level, electroactive polymer arrays are used to study mechanotransduction of individual cells. Ionic electroactive polymers show potential to be used in implantable electroactive biomedical devices. Already with the currently available science and technology, we are at the verge of witnessing the demonstration of truly complex bionic systems.

Dielectric elastomer actuators are considered as promising candidates for robotic elements. To this end, planar dielectric elastomer actuators (p-DEAs) and dielectric elastomer minimum energy structures (DEMES) are applicable. However, the knowledge of their electrical and mechanical characteristics is of major importance for engineering tasks. Therefore we study p-DEAs and DEMES by impedance spectroscopy (IS) and dynamic capacitive extensometry (DCE). We vary the boundary conditions with regard to p-DEAs (free and fixed boundaries) and fabricate various DEMES with one angular degree of freedom. A mixture of carbon black particles and silicone oil serves as compliant electrodes. We present equivalent circuit models of the actuators based on impedance spectroscopy data, the frequency ranges in which they are applicable and effects of aging on the equivalent circuit models. By DCE the electrical characteristics of dielectric elastomer actuators are monitored in situ during dynamic high voltage actuation. These electrical characteristics of the dielectric elastomer actuators such as p-DEAs and DEMES can be related to their transient stretch in response to high voltage driving signals. We study the viscoelastic response of the actuators to square driving signals of different magnitudes; furthermore we monitor the state of the compliant electrodes. By means of the DCE measurement data and the impedance spectra the p-DEAs and DEMES can be compared.

Mechanical energy and electrical energy can be converted to each other by using a dielectric elastomer transducer. Large voltage-induced deformation has been a major challenge in the practical applications. The voltage-induced deformation of dielectric elastomer is restricted by electromechanical instability (EMI) and electric breakdown. We study the loading path effect of dielectric elastomer and introduce various methods to achieve giant deformation in dielectric elastomer and demonstrate the principles of operation in experiments. We use a computational model to analyze the operation of DE generators and actuators to guide the experiment. In actuator mode, we get three designing parameters to vary the actuation response of the device, and realize giant deformation with appropriate parameter group. In the generator mode, energy flows in a device with inhomogeneous deformation is demonstrated.

We demonstrate the printing of a complex smart integrated system using only five functional inks: the fluoropolymer P(VDF:TrFE) (Poly(vinylidene fluoride trifluoroethylene) sensor ink, the conductive polymer PEDOT:PSS (poly(3,4 ethylenedioxythiophene):poly(styrene sulfonic acid) ink, a conductive carbon paste, a polymeric electrolyte and SU8 for separation. The result is a touchless human-machine interface, including piezo- and pyroelectric sensor pixels (sensitive to pressure changes and impinging infrared light), transistors for impedance matching and signal conditioning, and an electrochromic display. Applications may not only emerge in human-machine interfaces, but also in transient temperature or pressure sensing used in safety technology, in artificial skins and in disposable sensor labels.

Herein we report our recent efforts in employing natural materials and synthetic derivatives of natural molecules for organic field effect transistors (OFETs) and organic photovoltaics (OPVs). We evaluated dyes from the following chemical families: acridones, anthraquinones, carotenoids, and indigoids. These materials have proven effective in organic field effect transistors, with mobilities in the 4 × 10-4 - 0.2 cm2/V-s range, with indigoids showing promising ambipolar behavior. We fabricated complementary-like voltage inverters with high gains using indigoids. The photovoltaic properties of these materials were characterized in metal-insulator-metal (MIM) diodes, as well as in donoracceptor bilayer devices. Additionally, we have found that indigoids and Quinacridone, show long-range crystalline order due to hydrogen binding, and have considerably higher relative permittivities (e) compared to typical organic semiconductors. Higher permittivities result in lower exciton binding energies and thus may lead to high photocurrents in photovoltaic devices.

Electrically deformable materials have a long history, with first quotations in a letter from Alessandro Volta. The topic turned out to be hot at the end of the 19th century, with a landmark paper of Rontgen anticipating the dielectric elastomer principle. In 2000, Pelrine and co-workers generated huge interest in such soft actuators, by demonstrating voltage induced huge area expansion rates of more than 300%. Since then, the field became mature, with first commercial applications appearing on the market. New frontiers also emerged recently, for example by using dielectric transducers in a reverse mode for scavenging mechanical energy. In the present survey we briefly discuss the latest developments in the field.

Two major concerns in the world nowadays are the plastic consumption and waste. Because to the economic growth and the incessant demand of plastics in developing countries, plastics consumption is projected to increase by a factor of two to three during the actual decade 1 . As an intuitive example, the amount of municipal solid waste (estimated per person per year) averages ~440 kg for China, ~550 kg for the European Union and ~790 kg for the United States, with almost 50% of the waste being electronic products and plastics 1,2 . Green technology based on biodegradable/compostable materials is perceived as an ultimate goal for solving waste problems. Currently there are numerous efforts for producing compostable plastic materials for applications in daily life products, such as plastic bags and disposable dishware. When such low-end products are fabricated with compostable materials, electronics included in such goods should be also based on materials that are easily compostable.

Photo-induced phenomena were investigated in photoresposive organic field-effect transistors (photOFETs) based on conjugated polymer/fullerene solid-state mixtures as active semiconductor layer and divinyltetramethyldisiloxane-bis(benzocyclobutene) (BCB) as gate dielectrics. The devices were characterized both in under dark showing n-type transistor behaviour with linear and saturated mobility of 1.7 x 10 -3 cm 2 /Vs and 2.7 x 10 -2 cm 2 /Vs respectively, and under white light illumination condition, where large shifts in the threshold voltage in the transfer characteristics were obtained. A typical phototransistor behaviour in a wide range of illumination intensities are observed in these devices.

Dielectric elastomer actuators (DEA) considerably change shape when stimulated electrically and hold promise as artificial muscles. An electromechanical characterization protocol for DEA's is developed and tested with the VHB 4910 polyacrylic elastomer from 3M, where the current - voltage response of the actuator is recorded together with the area expansion from a video-extensometer until breakdown occurs. The current is a direct measure of the area expansion of the DEA and can be used to control the actuator. The modeling of the DEA is based on hyperelasticity models for elastomers. Minimum requirements for the strain energy function of dielectric elastomers are derived in terms of the principal stretching ratios guaranteeing stability against mechanical collapse of the actuator. The electromechanical characterization and modeling protocol developed may provide useful guidelines for the selection and assessment of new dielectric elastomer materials.

A large number of actuator geometries are known for dielectric elastomer actuators. It is known that pre-strain has a beneficial effect on the actuation output properties of dielectric elastomer actuators, though actuators without pre-strain have also been realized and proven to be of value. We would like to present a new concept for design of dielectric elastomer actuators which draws on conclusions from both approaches with, and without a pre-straining frame. With this concept, a large number of new actuator geometries can be visualized, and easily prepared.

Conjugated polymers are nowadays used in two different types of device. On the one hand, they act as electronically active semiconducting/conducting materials in organic electronic devices. On the other hand, one exploits them as electromechanically active materials since it has been observed that they can experience huge macroscopic strains upon electrochemical doping. We investigated the combination of these two effects by measuring the electromechanical behavior of typical polymeric electronic devices like rectifying (and/or light emitting) diodes. In the case of a poly(para-phenylene-vinylene) (MDMO-PPV) based diodes, we observed two types of electromechanical actuation. In the forward direction, a significant current (up to several mA/cm 2 ) is flowing. Joule heating induces a thermoelectrostrictive bending of the device substrate. In the reverse direction, the diode behaves like a capacitor. Therefore the strains are induced by Maxwell forces. For poly(3-hexyl-thiophene) (P3HT) based diodes, displacement versus voltage in the reverse direction revealed a power law with an exponent of 1.5. This surprising result can be modeled by Coulombic attraction of the doped impurities present in the depletion zone and the charges present in the metal at the interface.

Cellular space-charge electrets have emerged as a new class of materials for electromechanical devices, offering a huge potential for applications in noise reduction or cancellation, non-intrusive surveillance, advanced monitoring in health care, as well as in non-destructive testing. Here we report on piezoelectric responses in sandwich structures of two dielectric films separated by an air-gap of a few micrometer thickness. The sandwich structure is charged by dielectric barrier microdischarges within the air-gap. Wide ranging similarities to ferroelectric materials are demonstrated, like hysteresis loops in the dielectric and electromechanical properties versus applied voltage. Applications may emerge in electrostatic microelectromechanical devices.

Several adaptations of the well known thermal-pulse technique for the determination of the spatial distribution of polarization across the film thickness will be discussed, which enable the in-situ investigation of piezo-, pyroelectric, elastic and thermal material properties during i.e. thermal cycles and chemical reactions within one easy- to-use experimental setup. Illustrations of the techniques are given by employing ferroelectric polymers, as well as amorphous, photonics polymers. Pulsed electrothermal techniques are easy-to-use, fast, highly sensitive and reliable, and therefore suitable for opening broad new fields of research in thin film materials characterization.

Poled polymers are an exciting class of materials for second-order and third-order-like (cascading) nonlinear optical applications at the telecom wavelengths around 1.3 and 1.55μm, as material parameters can be tailored for each specific application. In this survey, the most recent developments in the field of second-order nonlinear optical polymers for frequency conversion and cascading are briefly reviewed. The material parameters required for efficient frequency conversion are critically discussed together with the waveguide preparation, electrical poling and in-situ characterization of the achieved nonlinearity for various phase-matched device schemes. The state of the art in achieved second-harmonic generation conversion efficiencies is documented and predictions on the possible further development of the field are made.