Low-Voltage-Driven Liquid Metal Microdroplet/Poly(vinyl Chloride) Gel Actuator for Smart Haptic Interaction Application

Electroactive dielectric elastomer actuators are highly promising for haptic interfaces due to their low noise, large deformations, and skin-compliant properties. However, their high driving voltage (several kilovolts, resulting from the dielectric constant-Young's modulus trade-off) and inherent in-plane actuation mode greatly limit their use in practical haptic devices. Herein, the characteristic trade-off between dielectric constant and Young's modulus is overcome by incorporating modulus-near-zero liquid metal (LM) microdroplets into dielectric poly(vinyl chloride) gel (PVCG), enabling large actuation strains under relatively low electric fields. Furthermore, the in-plane expansion deformation of the LM-modified PVCG actuator is effectively converted into a pronounced out-of-plane actuation mode by leveraging the unique microscopic creep deformation mechanism and mesh-like electrodes. As a result, the optimized PVCG actuator demonstrates a 1.6-time improvement of the electromechanical coupling sensitivity coefficient and a 1.8-time enhancement of out-of-plane actuation displacement compared to its unmodified counterpart at a low electric field of 3.75 V μm^-1 (750 V). Finally, a compact, low-voltage-driven haptic device prototype is fabricated based on the developed PVCG actuators, and its practical applications are demonstrated. The haptic device delivers a remarkable out-of-plane actuation strain of 20% and an output stress of 1.5 kPa, both well within the perceptible range of human skin mechanoreceptors. These results highlight the significant application potential of the presented PVCG actuator and device in the fields of virtual reality/augmented reality and assistive navigation communication for the blind.