Review of recent developments in capacitor-type heat flow switching devices

This review summarizes our recent developments in capacitor-type heat flow switching devices that enable active control of heat flow magnitude through the modulation of electron thermal conductivity. We initially demonstrated the feasibility of a capacitor-type heat flow switching device using silver chalcogenides, Ag₂S_1-x Se _x , as an electrode material with very low lattice thermal conductivity (≤0.5 W m^-1 K^-1). We achieved significant enhancements in heat flow switching performance through subsequent improvements, including electrode thinning and the implementation of an electric double-layer capacitor structure with ionic liquids. The switching ratio improved from an initial value of 1.1 at the bias voltage of V _B = +3 V to 1.9 at V _B = +2.4 V, while response times were estimated to be less than 0.2 s. This review discusses the operating principles, experimental methods, and performance metrics across different device configurations, highlighting the critical role of electrode materials with extremely low lattice thermal conductivity. Our findings establish a promising candidate for practical thermal management applications that require rapid and reliable heat flow control without mechanical components.