Plasticized PVC/CNT Flexible Electrodes for Highly Responsive, Stable, and Durable Soft Actuators and Wearable Sensors

Abstract

Plasticized polyvinyl chloride (PVC) gels have shown increasing potential for developing integrated actuation and sensing devices in soft robotics and wearable electronics. Notably, the flexible electrodes in PVC gel-based devices are crucial to their overall performance. However, traditional carbon grease electrodes substantially limit the functionality and stability of such devices, primarily due to their uneven distribution and inherent durability. To address these limitations, we propose a novel PVC/carbon nanotubes (CNTs) gel electrode (GE) for constructing dual-mode actuation-sensing devices with high performance and stability. We investigated the effects of three representative fillers-carbon black, graphene, and CNTs on the formation of molecular networks of the gel. Owing to its intrinsic one-dimensional geometry, CNTs facilitate the formation of a 3D percolating network, enabling PVC/CNTs GE (PCGE) to achieve an unprecedented charge carrier density of 3.31×10¹⁷ cm⁻³. The PCGE demonstrates a high electrical conductivity of 79.9 mS/cm (4.2 times higher than carbon grease), an ultralow 30-day impedance growth rate of 8.4% (a 70-fold reduction), and a minimal 10,000-cycle drift of 1.25%(a 51-fold improvement), surpassing carbon grease in both conductivity and durability for flexible electronic applications. The PCGE-based bending actuators exhibited remarkable performance (182° at 3 V/μm) and a fast response (2 Hz). Moreover, the PCGE-based sensors achieved high sensitivity (GF>35), precise resolution (0.06%), and ideal dynamic response (0.5-4 Hz), addressing the durability limitations of carbon grease. Additionally, the actuators achieve biomimetic applications in robotics, demonstrating their potential as artificial muscles. In contrast, the sensors enable motion tracking, showcasing broad applicability in intelligent sensing systems.