Case Studies of Surface Engineering Applications in Thermo/Fluidic Systems

Surface wettability engineering is a robust technique for manipulating liquids and gases on open surfaces in isothermal and non-isothermal conditions. In this work, five different applications of surface wettability engineering have been investigated. In two isothermal cases, the wettability properties of a multi-component nanoparticle coating (TiO2) were studied as a function of composition and UV irradiation time required to reach certain wettability. Several machine learning methods were employed to develop a model predicting a particular composite's required UV exposure time to reach a prescribed wettability. As shown in a separate application, wettability patterning is also well suited for confining and controlling gas bubbles on tracks submerged in liquids. A parametric study for various combinations of track geometry, liquid properties, and gas bubble sizes was performed to develop a scaling law describing the spreading of mm-size gas bubbles on wettability-confined superaerophilic tracks submerged in a liquid. In separate non-isothermal cases, the application of wettability engineering for heat transfer enhancement was also explored. Initially, the role of the superhydrophilic wedge-shape track's pressure gradient in condensation heat transfer enhancement was theoretically and experimentally studied. It was shown that the superhydrophilic wedge-shape track's design plays a major role in the condensation heat transfer performance of a solid surface. This technology was implemented in two passive heat spreaders; a vapor chamber and a heat pipe, to show application in thermal management systems. It was shown that a wickless wettability-patterned surface could reduce the condensation heat transfer thermal resistance, which in turn, reduced the overall thermal resistance of the device. Moreover, the wettability-patterned surface enhanced the working liquid circulation inside the heat-spreading device and consequently, improved its thermal performance. The examples in this thesis show that the wettability patterning approach has the potential to improve the performance of thermal management components, thus reducing the risk of chip failure and facilitating energy savings in these systems.