|Posted on February 5, 2015 at 9:00 PM|
We are increasingly being told to keep hydrated and this is certainly a major concern for inhabitants of the Namib desert. Some Namibian beetles have evolved to solve this problem by a patchwork quilt of hydrophilic and hydrophobic patches on their back which condense and collect water. The dilemma involves creating surfaces that can satisfy competing efficiency of condensing water and heat transfer concerns. Beetles solve the problem by contrasting surface properties - hydrophobicity and hydrophilicity. On a hydrophilic surface, the condensation efficiency is high but the heat transfer efficiency is low, while the opposite is true on a hydrophobic surface. The efficiency of the condensation and the heat transfer coefficient of the condensed liquid are key parameters that can be tuned to make effective applications out of vapor condensation.
(From left: Prof. Shuhuai Yao, Graduate students Miao Yu and Youmin Hou).
Associate Prof. Shuhuai Yao (mechanical and aerospace engineering, Hong Kong University of Science and Technology) and her research group proposed a solution to this challenge, inspired by the Namibian desert beetles. They designed a hybrid material, which was featured on the cover of ACS Nano on January 27th, 2015, that consisted of hydrophilic nanopillars that induce efficient condensation and hydrophobic nanograss surrounding the pillars which induces a drop-wise condensation that delivers a high heat transfer coefficient. In the article, the researchers showed that the heat transfer coefficient was increased by 63%, when compared with the conventional flat hydrophobic surface.
(SEM Image of the hybrid nanostructured silicon surface consisting of micropillar arrays and surrounding nanograss. Scale bar-10 micrometers. (Figure 1(B) from the article).)
Prof. Yao's research interest lies in investigating micro/nanoscale fluid dynamics and interfacial surface science. More information about her research projects can be found on her website.
(Images of condensation modes observed across the surfaces with different wettability. Scale bar – 300 micrometers. (Figure 1(A,B,C,D) from the article)).
(Photo credits: Group: Provided by and used with permission from Shuhuai Yao, credit to: Matthew Lai; Science: Reprinted with permission from (Youmin Hou, Miao Yu, Xumei Chen, Zuankai Wang, and Shuhuai Yao. Recurrent Filmwise and Dropwise Condensation on a Bettle Mimetic Surface, ACS Nano, 2015, 9(1), pp 71-81). Copyright (2015) American Chemical Society.)