A Pressure-Driven Microfluidic Electrical Switch Array Embedded in a Flexible Matrix

Abstract

Microfluidic devices offer the possibility to manipulate tiny amounts of fluid on a small area footprint. This paper presents a novel microfluidic electrical switch array embedded in a flexible polydimethylsiloxane matrix, utilizing the high electrical conductivity and surface tension of eutectic gallium-indium-tin alloy (Galinstan) for controlled fluid movement and electrical switching. By applying a differential pressure across a microchannel pre-filled with NaOH, Galinstan is driven through constrictions to toggle electrical switches at predetermined pressure thresholds. These thresholds are governed by the capillary pressure exerted on Galinstan in the constrictions. Each switch is closed when Galinstan bridges two co-planar electrodes. Experimental results demonstrate reliable and tunable switch activation based on the microchannel geometry, showcasing the potential for reconfigurable, liquid metal-based microfluidic circuits. The flexible design allows for integration into soft robotics and environmental sensing applications, offering a scalable solution for pressure-sensitive electronic interfaces in microfluidic devices.