A thermal switch regulates the heat flux by switching the thermal conductance of two-terminal components in "on" and "off" states P. Hu and J. Wang, Device 1, 100095 (2023). We present a novel ferrofluid-based reversible thermal switch that modulates thermal conductance by formation and breakup of ferrofluid bridge between two surfaces using a periodic magnetic field. The lifetime of the bridge is controlled by adjusting the "switch on" and "switch off" times of the electromagnet. Heat is transferred from the heated substrate to cold surface (cold well) through ferrofluid bridge of high thermal conductivity. The temperature of the heated substrate decreases as the switching frequency (f) increases, and effective cooling is observed at critical switching frequency, fc = 0.5 Hz. The effect of magnetic field on interfacial tension influences the shape of the hump and the liquid bridge formation process. The cooling of the substrate is associated with lifetime of the ferrofluid bridge and velocity of the liquid-air interface during the switch-on state of the thermal switch.
Saroj et al. (Sun,) studied this question.