Enhancement of evaporative heat transfer on carbon nanotube sponges by electric field reinforced wettability

Phase-change thermal management devices are the most effective approach to managing the increasing redundant heat in integrated electronic chips. The cooling performance of phase-change thermal management devices can be obviously enhanced via micro- and nano-structured materials with special wettability. Here, carbon nanotubes (CNTs) sponges are fabricated, and the strategy to enhance evaporative heat transfer properties on the CNTs sponges by electrowetting method is presented. The electrowetting method induces a higher degree of wettability of porous CNTs sponges, which results in spreading and even permeation of the liquids without any physical or chemical treatment. In this case, the electrowetting method could lead to a much better evaporative heat transfer properties. Specifically, evaporation areas and evaporation rates of liquids on CNTs sponges are enlarged about 5-7 times and 2.8-10.5 times by the electrowetting method, respectively. The electrowetting method also induces much better temperature uniformity properties that play vital roles in phase-change thermal management devices. The CNTs sponges also have chemical stability and are light-weight versus traditional metallic materials. Thus, our work reported here is a promising opportunity to enhance the evaporative heat transfer properties of liquids with a profound influence on thermal management techniques.