Switch Controls the Flow of Heat to Improve System Performance and Reliability

Achievement date: 

A new millimeter-scale switch that controls the flow of heat in dense electronics was developed by researchers at the Center for Power Optimization of Electro-Thermal Systems (POETS), an NSF-funded Engineering Research Center (ERC) based at the University of Illinois.


The need for thermal control has become particularly urgent with the growing density of electronics and resulting intense heat fluxes. Thermal switches, capable of modulating between areas with high or low tendency to conduct heat, enable the partitioning and active control of heat flow pathways. Such switches can enable the manufacture of electronics packed ever more tightly for efficiency and lower cost.


The technology is based on the motion of a liquid-metal droplet. Essentially, the metal droplet can be positioned to connect a heat-flow path, or moved away from the path to limit the flow. The device consists of a silicone channel filled with a reducing liquid or vapor and an immersed liquid-metal Galinstan slug. Galinstan has a relatively high thermal conductivity, and its position can be manipulated within the fluid channel, using either hydrostatic pressure or electric fields.

When Galinstan bridges the hot and cold reservoirs in the “ON” state, heat flows across the channel. When the hot and cold reservoirs are instead filled with the encapsulating liquid or vapor in the “OFF” state, the cross-channel heat flow significantly reduces due to the lower thermal conductivity of the solution.