Developing Supernucleating Surfaces Featuring Hierarchical Morphology and Tunable Wettability for Enhanced Two-Phase Heat Transfer

The engineering of robust supernucleating surfaces that promote the phase change processes (condensation/boiling) would have broad technological implications, but has proved extremely challenging. Conventional condensation or boiling surfaces are limited by the capability to provide adequate nucleation sites, and at the same time delay the onset of the undesired liquid (in the case of condensation) or vapor (in the case of boiling) film. This proposal will address this challenge by designing and fabricating novel supernucleating surfaces featuring hierarchical morphology and tunable wettability for superior dropwise condensation or nucleate boiling. Moreover, these individual supernucleating surfaces can be further synergistically integrated together to construct a novel vapor chamber for thermal management of high heat flux. The project will build on the PI's past success in the investigation of interfacial and transport phenomena on micro/nanostructured surfaces and exploration of such surfaces for heat transfer applications.To realize these goals, we propose the following tasks. (1) Develop a novel hierarchical architecture for enhanced dropwise condensation or nucleate boiling through rational control of the physical and chemical properties of the surface. (2) Systematically investigate the condensation phenomenon on hierarchical and chemically homogeneous surfaces. We will elucidate the roles of multiscale roughness on droplet condensation and measure the condensation heat transfer coefficient. (3) Study the nucleate boiling phenomenon on hierarchical but chemically heterogeneous surfaces. We will perform visualization of bubble nucleation dynamics in real-time mode and investigate how the multiscale roughness and chemical heterogeneity impact the macroscopic boiling heat transfer performances. (4) As a technology demonstration, we will assemble the supernucleating surfaces into a vapor chamber, which offers the potential to significantly enhance the thermal performances. Moreover, since the condensate drops come back to the boiling surface by spontaneous departure, our chamber might eliminate the need of additional wick structures for liquid return.We believe the implementation of the proposed project could not only advance our fundamental understanding of underlying physics governing the multi-phase phenomena on micro/nanostructured surfaces, but also open a new avenue for the development of novel thermal management devices where phase change plays an important role. The results of the project will provide new classroom materials for undergraduate courses as well. The ECS project will enable the PI to continue his research work in a sustained and focused manner, laying the foundation for a lifetime of integrated research and teaching contributions in the areas of thermal-fluidics, nanomaterials, and surface science.