Voltage-controlled pattern transition of liquid metals in disordered porous media.

Liquid metals (LMs) have emerged as promising materials in microfluidic systems due to their unique combination of metallic conductivity and fluidic properties, enabling applications in soft electronics, robotics, and reconfigurable circuits. While LMs have frequently been utilized as static components, their dynamic behaviors, particularly their flow patterns in complex microchannels upon different electric voltages and flow rates, remain rarely studied. Understanding voltage-induced pattern transitions, driven by capillary, electric, and Marangoni effects, is crucial for practical device integration. In this study, PDMS-based microfluidic chips were fabricated to systematically investigate the flow behavior of LMs under varying voltages and flow rates. Results show that LM flow patterns are highly dependent on the interplay of voltage and flow rate. At high flow rates, voltage effects diminish, whereas at low flow rates, voltage-induced transitions are observed: from finger-like displacement to tree-like displacement to discontinuous flow, attributed to Marangoni-driven interfacial dynamics. A theoretical model incorporating force balance and interfacial phenomena was proposed to quantify voltage-driven transitions. Our results provide critical guidelines for optimizing microfluidic parameters for LM applications.