Drs. William King and Nenad Miljkovic with collaborators at the University of Illinois at Urbana-Champaign have developed a millimeter-scale high-contrast thermal switch that can be used for cooling in power electronics and a variety of other electrical and thermal power systems. This liquid-metal based, electrically-controlled thermal switch controls heat transfer of thermally sensitive systems with hotspots smaller than 1 mm and as large as 1 cm and beyond. This technology has a high switching ratio (>10), high switching speed (>1Hz), and it utilizes liquid metal alloys with reduced toxicity, high thermal conductivity and surface tension. Liquid-based thermal switches are the most promising solutions for thermal management at room temperature. They allow to reduce the contact thermal resistance, enhance the operational speed and reduce heat losses. This new device will enable development of thermal circuit in the electrical and thermal power systems on a practical level.