Controllable Design of Bifunctional VO2 Coatings with Superhydrophobic and Thermochromic Performances.

The structure and functions of natural organisms provide great inspirational sources for designing and manufacturing bionic coatings, which hold a distinguished scientific promise to tackle challenges facing humans. In this work, we report a facile and controllable approach to prepare various hexagonal periodic array VO2 thin films by simply manipulating the speed of the dip-coating operation. The hexagonal cellular-structured VO2 surface delivered the best thermochromic performance with a Tlum of 79.34% and a ΔTsol of 9.87%. Impressively, superhydrophobic and thermochromic properties could be integrated into hexagonal semi-dome thin films (with a Tlum of 70.9%, a ΔTsol of 9.3%, and a water contact angle of 150°) without any post-treatment by low-surface-energy chemicals, which hold considerable potential for application in multifunctional smart windows. Moreover, based on the Cassie-Baxter mode and finite-difference time-domain calculations, the dependence of the thermochromic and wettability performances on the VO2 structure has been investigated in this study.