Design and Modeling of Electrohydrodynamically Driven Droplets for Fluid Joints Microactuators

Microscale actuation holdsx transformative potential across various fields by enabling precise and minimally invasive actions; however, downsizing actuators while keeping relatively large actuation range is challenging. Electrohydrodynamics (EHD) forces, arising from electric field–fluid interaction, can greatly deform fluid surface at microscale, yet there is a lack of knowledge regarding the modeling, control, and specificity, which hinder their use in microactuator designs. This article, aims to design, model and open-loop control a droplet driven by EHD, focusing on its application in fluid joints (i.e., two solids link together by a liquid droplet)-based microactuators. The model merges an energy-based steady-state hysteresis with linear dynamics, using the steady-state inverse as an open-loop controller to control the droplet's height. For a selected design, both steady-state and dynamic models were fitted using a 3
$\mu$
L droplet of glycerin, and the control strategy was tested. The model accurately predicts the stable droplet position, while the control strategy maintains a height error under 14
$\mu$
m, a motion amplitude of 150
$\mu$
m, and high repeatability. This article contributes to the advancement of microscale actuation by presenting a model and open-loop control strategy for EHD-driven droplets, facilitating practical use as a microactuator for fluid joints in microrobotic applications.