Adaptive Chip Cooling Using Electrowetting on Coplanar Control Electrodes

As a result of the increasing speed, expanding functionality, and decreasing size of microprocessors and integrated chips, heat dissipation power density has been rapidly growing over the past two decades. Advanced cooling techniques to meet this rising demand are crucial. Recently, electrowetting transport of liquid droplets has drawn significant interest in thermal management because of its digital programmable and reconfigurable characteristics. With a two-dimensional array of control electrodes patterned on a surface, cooling droplets can be transported along a programmable path to a hot spot without the need for mechanical moving parts. For adaptive cooling of electronic devices using electrowetting, we designed novel coplanar control electrodes, in which the electrode units were used interchangeably as the activating and the ground electrodes. In this article, we report electrowetting actuation of liquid droplets along specially designed control electrodes in an open-plate configuration. At the chip level, one water droplet of 14 L transmitted by our actuation mechanism can rapidly cool down a hot spot of 27 W/cm2 by as much as 30 degrees C. Furthermore, in a parallel-plate configuration with carbon nanotubes (CNTs) grown on the cover plate, our test results indicate that multiscale roughness can lead to superhydrophobicity and electrowetting transport over the superhydrophobic surface can reduce the pressure loss significantly.