Thermal micro pumps for a loop-type micro channel

We have developed thermal micro pumps for a loop-type micro channel, realizing an active micro heat transport device capable of highly efficient cooling. The thermal micro pumps make use of the time change in the vapor pressure of the working fluid as the driving force for fluid circulation. Because it has no mechanically moving elements, it is highly reliable and moreover is effective in preventing the deterioration of the heat transport rate due to miniaturization. First we fabricated an experimental loop-type micro channel with one thermal micro pump as the basic study. The circulation rate of the fluid was confirmed to be 2 mm/s at the heat calorific power of 0.7 W (2 Hz). In order to improve the circulation rate of the fluid, we set up a system with two thermal micro pumps within one loop to repeat evaporation and concentration alternately in the micro channel so as to enable the absorption of the volume change within the micro channel. Further, we made improvements not only to enable the use of the difference in the channel resistance between the valves but also the difference in the capillary diameter. We fabricated a U-shaped double loop micro channel, which has a width of 600 μm, a depth of 120 μm and a channel length of 220 mm. We confirmed a flow rate of 12.5 mm/s at the driving frequency of 1 Hz, enabling a heat transport of 0.16 W.