Bio-Inspired Superhydrophobic Closely Packed Aligned Nanoneedle Architectures for Enhancing Condensation Heat Transfer

Bionic condensate microdrop self-propelling (CMDSP) surfaces are attracting intensive interest due to their academic and commercial values. Up to now, it is still a great challenge to design and fabricate CMDSP nanostructures with superior condensation heat transfer (CHT) efficiency. Here, it is reported that the CHT coefficient of copper surfaces can be enhanced maximally approximate to 320% via in situ growth and geometric regulation of closely packed aligned nanoneedles with CMDSP function. These experiments and theoretical analyses indicate that reducing the interspaces of nanoneedles can help reduce the departure diameters of condensate microdrops and increase their nucleation density, both of which are beneficial to enhance CHT. In contrast, increasing the tip size and height of nanoneedles can increase drop departure diameters and film-layer thermal resistance, respectively, either of which is disadvantageous to enhance CHT. Clearly, only considering superhydrophobic effect is insufficient and both choosing ideal nanoarchitectures and optimizing their geometric parameters are very crucial to realize high-efficiency CHT, which optimization can be achieved via simply controlling growth time of nanostructures. These findings offer new insights into the design and development of first-rank CHT interface nanomaterials.