High-switching-ratio liquid metal-based thermal switch enabled by electromagnetic actuation: flow evolution and heat transfer

The advancement of micro/nano-electronics and power battery technologies has led to increasingly severe heat dissipation challenges. Electromagnetically actuated liquid metal-based thermal switches with high switching ratios enable effective heat flow control in electronic devices. However, the dynamic coupling between liquid metal droplet motion and transient thermal response remains poorly understood. This work systematically investigates the flow pattern evolution and dynamic heat transfer characteristics of a gallium-based liquid metal droplet in a microchannel under electromagnetic actuation, by combining theoretical analysis, numerical simulations, and visualization/heat transfer experiments. The results reveal five distinct stages of droplet motion, with morphological evolution governed by the synergistic effects of electromagnetic force, interfacial tension, and inertia. Dynamic heat transfer is strongly correlated with droplet motion. The heat flux response lags behind droplet motion due to thermal hysteresis caused by the mismatch in thermal diffusivity between the liquid metal and copper plates. Visualization experiments confirm the multi-stage flow evolution of the droplet, with a velocity response time of approximately 0.3 s. Heat transfer experiments demonstrate that the switching ratio increases with actuation voltage, reaching up to 14.9, primarily due to enhanced droplet filling efficiency. These findings elucidate the mechanisms governing flow pattern evolution and provide quantitative guidance for the design of high-performance thermal switches.