Asymmetric PEDOT:PSS Trilayers as Actuating and Sensing Linear Artificial Muscles

Abstract Soft ionic actuators and sensors have been intensively studied over the last 20 years. The bending trilayer configuration has been considered a standard architecture, allowing the development of new materials and their optimization. However, bending deformation remains low in force output and presents limited integration capabilities in fast emerging fields like humanoid robotics and actuating textiles. A generalizable architecture of asymmetric supercapacitor‐like trilayers is presented to develop open‐air linear artificial muscles that actuate and sense. First, tuning of electromechanical properties of asymmetric electrodes is performed separately by combining poly(3,4‐ethyl‐enedioxythiophene):poly(styrene sulfonate) with a polyethylene oxide network and 1‐ethyl‐3methylimidazolium bis(trifluoromethanesulfonyl)imide as additives. By varying their content, electronic conductivity can be tuned between 20 and 457 S cm⁻¹, Young's modulus from 1.5 to 0.27 GPa, and volumetric charge density increased by 36%. Asymmetric trilayers are then fabricated using a simple layer stacking process by selecting the optimal combination of materials according to an electromechanical model. Linear strain of 0.5% is obtained in 30 s under ±2 V with 70% of the deformation within 5 s and blocking stress as high as 0.3 MPa. When mechanically stimulated, these asymmetric trilayers demonstrate linear sensing as well, with a sensitivity of 0.38 mV %⁻¹.