Electroactive polymers cover a broad spectrum of actuation properties. Conjugated polymers (CP) can be electrochemically doped and undoped at low voltages. Dielectric elastomers (DE) require high voltage to output large force and high strain. Side-chain crystallizable polymers (SCP) exhibit three orders of magnitude change in stiffness during the reversible melting and recrystallization of the side chains. SCP behave like the DE at the soft state, and can thus be explored for bistable actuation. SCP also exhibit other important properties resulted from the phase change. These material research and device exploration undertaken at our Soft Materials Research Lab will be presented.

Dielectric elastomer fiber actuators can respond to external stimuli and thereby mimic natural muscles. In this work, we developed a continuous wet spinning method to prepare silicone fibers using a photocurable thiol-ene reaction. The optimized fiber exhibits seven times higher tensile strain and five times greater tensile strength compared to those of the planar film. The developed fiber actuator exhibits a large and stable linear actuation strain. The work presented herein provides a pathway for creating active soft matter with complex architectures to enable fast programmable actuation for multiple applications including artificial muscles.

Polymeric gel-based artificial muscles exhibiting tissue-matched Young’s modulus (10 Pa-1 MPa) promise to be core components in future soft robotics with inherently safe human-machine interactions. However, these materials are still in their infancy, and many significant challenges remain presenting impediments to their practical implementation, including poor mechanical properties, slow actuation speed and limited actuation performance. In our study, we propose molecular design principles to overcome these limitations. First, our molecular design concepts to improve mechanical properties of hydrogel actuators will be introduced. I will also talk about our strategies to realize fast actuation speed. In addition, how to design strong and fast hydrogel actuators will be discussed. Finally, our recent progress in realizing high values in several aspects of actuation performance metrics for this class of materials will be introduced.

There have been many challenges over the past 20 years to bring Dielectric EAP technology to commercial viability. Aside from exhaustive R&D efforts, manufacturing at reasonable costs and market adaptation are two of the biggest. This presentation will explore this history from the original start of Artificial Muscle Inc. through Bayer’s commercial launch of the ViviTouch haptics product line to the technology’s current commercial landscape. This review will give an inside look at where markets rejected the technology and how it eventually became successful with DE sensors. It will give a view into the innovative materials and designs that underpin EAP sensors, highlighting their adaptability for various sensing functions such as strain and pressure. It also addresses challenges and prospects in the commercialization of EAP sensors, including manufacturing scalability, reliability, and integration with existing systems. Furthermore, it explores potential future directions for EAP sensor technology and its role in shaping the industry's future.

The processing of multilayer dielectric elastomers (DE) allows to improve the structural integrity of dielectric elastomer transducers (DET) and facilitates novel transducer concepts. In particular, the buckling dielectric elastomer transducer (BDET) is a promising loudspeaker concept with good performance and simple design. This presentation gives an overview about recent advances in the manufacturing and theoretical description, which allow optimization of the loudspeaker.

This study socus on developing actuators from continuous fibrous conjugated polymers. Two distinct strategies are investigated: First, we introduce a wet-spinning process for PEDOT: PSS fibers without the use of a passive support fiber, followed by a subsequent electro-polymerization of polypyrrole onto the fiber. Additionally, we introduce a device designed for the continuous electro-polymerization of filamentary, free-standing polypyrrole tapes, utilizing a rotary disc electrode. Our findings reveal that the mechanical properties of pure PEDOT: PSS fibers and polypyrrole-coated PEDOT: PSS fibers significantly surpass those of the produced polypyrrole tapes. Moreover, both the spun fibers and polypyrrole tapes exhibit remarkably high electrical conductivity. We also conduct a comprehensive analysis of their electromechanical performance and provide a comparative assessment.

We developed a novel carbon black (CB) ink and tailored it for compatibility with the small cartridge nozzles (17x17 µm) of inkjet printers. With this ink, we printed a precise pattern on a dielectric elastomer membrane (VHB). By combining a dielectric elastomer actuator (DEA) next to the printed CB pattern, its resistance could be significantly changed (> 3 orders of magnitude) accompanied with actuation and non-actuation of the DEA. Thanks to its excellent piezoresistive performance, we have successfully applied this dielectric elastomer-based device as a “switch” for controlling soft grippers and as a multiplexer for signal processing.

In this talk, exciting possibilities of utilizing twisted and coiled actuators in heat engines to generate mechanical work will be discussed

Soft electrohydraulic (SEH) actuators are novel smart technology, which include the EPIC actuator, HAXELs, and the original SEH, the HASEL actuator. The HASEL actuator improves upon the dielectric elastomer actuator (DEA), by including a hydraulic component as a means to create a large strain. To better understand the complex electro-hydro-mechanical (EHM) process and dynamics of the actuator, this study applies dimensional analysis. Eight dimensionless Π groups are developed that describe the dynamics a SEH actuator, specifically the HASEL actuator. The performance of the actuator is characterized using the dimensionless Π groups and experimental testing results. From this study, the use of dimensionless analysis is shown to be effective in characterizing the performance of the HASEL actuator.

This study explores the development of an artificial lateral line system using electroactive polymer (EAP) sensors, specifically, ionic polymer-metal composites (IPMCs) and polymer gels. A TPU-based canal structure was 3D printed with two embedded surface TPU-DBA polymer gel sensors at each pore entrance, enabling the detection of hydrodynamic pressure changes in the surrounding fluid environment. Additionally, a single IPMC sensor enclosed within a PDMS cupula-like structure was placed in the center of the canal, emulating the cilium structure of the lateral line by operating as a bending mechanoelectrical transducer. The results validate the efficacy of the proposed artificial lateral line model.

Among the soft elastomers used for dielectric elastomer actuators (DEAs), silicone elastomers have excelled due to their high elasticity, robustness, and biocompatibility. However, silicone elastomers have a low dielectric constant and require the use of high voltages, which might not be considered safe in wearable applications. In this work, we propose the incorporation of biologically tailored materials in silicone elastomers to improve the dielectric properties and provide mechanical stability. The amyloid proteins are semicrystalline and, thus, offer a biologically derived and biocompatible analog to the synthetic polymer dielectrics traditionally used in high electric field environments. It has been proven before that the crystallinity and orientation of the proteins can be used to tailor the breakdown strength (200-400 V/µm for fibroin protein). Our approach uses genetically engineered proteins, which display a small peptide/protein domain and thereby the dielectric properties can easily be modulated.