Electrocapillary Modulated Interfacial Tension Amplifies Liquid Metal Transduction

ABSTRACT

Increasing the output power and performance limits of robotic actuators typically requires a significant increase in the complexity and size of the driving systems, or is achieved by trading off stress against strain or pressure against volumetric flow rate.   Here, we present an electrically controlled soft electrocapillary‐enhanced magnetohydrodynamic pump (EMP) that achieves both stress and strain amplification simply through electrocapillary biasing without added mechanical complexity. In this system, we utilise an active liquid metal droplet as the functional element, exploiting the high surface tension of eutectic gallium–indium (EGaIn) to facilitate self‐oscillating actuation. The EMP exploits the electrocapillary mechanism—where applied voltage modulates interfacial tension gradients—to bias the magnetohydrodynamic pumping action and thereby increase both pressure and flow. Combining low‐voltage magnetohydrodynamics (mean < 0.1 V) and low‐voltage electrocapillary biasing (0.5–2 V), the EMP achieves seamless miniaturisation within soft, compliant architectures. Acting as an internal amplifier, the electrocapillary effect increases fluidic output energy by a factor of 3.5 without requiring additional structural complexity and with neglectable input power (0.083%). This approach provides a scalable pathway toward integrated high‐performance fluidic systems for next‐generation lab‐on‐a‐chip platforms, soft machines, and wearable robotics.