Hot-Spot Cooling


In recent years, thermal management has become an important parameter in designing and manufacturing high-performance electronic devices including microprocessors. As a result, conventional cooling methods for integrated circuits will eventually fail to address the needs for high-performance computers. Here, a layer with variable and programmable thermal conductivity is placed between the electronic device and a conventional cooling system. This layer is composed of an array of liquid metal drops which can be actuated with the electrowetting phenomenon. The conductivity of this layer can be modified according to the heat transfer requirements of the system in the desired region. This action is accomplished by actuating the drop in that region with an applied AC voltage. Figure below shows the actuation of the drop using electrowetting phenomenon which causes the drop to detach from the top surface.



Actuation of a mercury drop with electrowetting phenomenon. (a) The drop is attached to the top surface. (b) After applying 310V, the drop is detached from the top surface.


If it is assumed that the top of the drop is a heat source while the bottom surface acts as a heat sink, then the attachment/detachment of the drop to the top surface can change the value of thermal conductance between the heat source and the heat sink. Figure below shows the temperature variation of the heat source against time while the rate of heat generation in the top surface is equal to 720 W/mm3. It can be seen that upon detachment of the drop from the top surface (i.e. surface of the heat source), the temperature of the heat source is increased. 



Variation of the heat source temperature before and after the detachment of  a 7 μL mercury drop from the surface of the heat source.

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