Soft Actuators with Integrated Electrohydrodynamic Pump and Intrinsic Electroadhesion

Abstract

Electrohydrodynamic (EHD) pumps made from flexible or stretchable materials are a promising pumping element for fluidically driven soft robots. In most soft robotic systems, EHD pumps are used separately or connected in series with their target components, such as actuators, which can limit design flexibility and complicate implementation. To address this issue, this paper presents an EHD soft actuator that integrates a pump, actuator, and reservoir into a single device. In this design, the EHD pump is implemented as a flexible PCB, which also serves as a strain-limiting layer, enhancing bending actuation. Additionally, the interdigitated electrodes on the flexible PCB generate fringe electric fields, introducing electroadhesion as an unprecedented functionality for EHD-driven soft actuators. Experimental results from the fabricated actuators demonstrate voltage-controllable actuation, achieving a maximum bending angle of 56.0° and a force of 31.0 mN. The actuators are then incorporated into a soft gripper, where electroadhesion enhances the holding force, with a 1.3× increase for a dielectric object and a 2.9× increase for a conductive object. These enhancements are observed in comparison to a control experiment in which gripping is performed using non-electric, fluidic actuation alone. The results validate the successful implementation of the highly integrated, multifunctional EHD soft actuator, highlighting its potential for soft robotic applications.