Hierarchically Branched Siloxane Brushes for Efficient Harvesting of Atmospheric Water |
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Authors: | Jiayu Song Jie Liu Meng Li Shuai Li Michael Kappl Hans-Jürgen Butt Youmin Hou King Lun Yeung |
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Affiliation: | 1. Department of Chemical and Biological Engineering, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China;2. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany |
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Abstract: | Atmospheric water harvesting is considered a viable source of freshwater to alleviate water scarcity in an arid climate. Water condensation tends to be more efficient on superhydrophobic surfaces as the spontaneous coalescence-induced droplet jumping on superhydrophobic surfaces enables faster condensate removal. However, poor water nucleation on these surfaces leads to meager water harvest. A conventional approach to the problem is to fabricate micro- and nanoscale biphilic structures. Nonetheless, the process is complex, expensive, and difficult to scale. Here, the authors present an inexpensive and scalable method based on manipulating the water-repellent coatings of superhydrophobic surfaces. Flexible siloxane can facilitate water nucleation, while a branched structure promotes efficient droplet jumping. Moreover, ToF-SIMS analysis indicated that branched siloxane provides a better water-repellent coating coverage than linear siloxane and the siloxanes comprise hydrophilic and hydrophobic molecular segments. Thus, the as-prepared superhydrophobic surface, TiO2 nanorods coated with branched siloxanes harvested eight times more water than a typical fluoroalkylsilane (FAS)-coated surface under a low 30% relative humidity and performed better than most reported biphasic materials. |
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Keywords: | branched siloxane brushes superhydrophobic surfaces vapor condensation water harvesting water-repellent coating |
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