Choubey Rakesh, Rowthu Sriharitha
Materials Engineering, Indian Institute of Technology (IIT) Gandhinagar, Gandhinagar 382055, Gujarat, India.
ACS Omega. 2024 Jun 19;9(26):28323-28338. doi: 10.1021/acsomega.4c01623. eCollection 2024 Jul 2.
Robust rain-repellent surfaces are useful in roofs, solar panels, windshields, etc. Herein, excellent rain-repellency and droplet bouncing properties of leaves are presented. They possess surface microbumps ( ∼ 13 μm, ∼ 8 μm, ∼ 3 μm), which in turn comprise nanoplatelets ( ∼ 741 nm, ∼ 59 nm) and Wenzel roughness ( ) of ∼2.2. The leaf's surface energy was estimated to be 9.47 ± 0.03 mJ·m by incorporating r into the van Oss-Good-Chaudhary theory. The leaves exhibited static contact angle of 157 ± 1°, roll-off angle of 9 ± 1°, and contact angle hysteresis of 12 ± 4°, which retained as they aged up to 186 days in the natural weather and laboratory conditions. The water droplets (10 μL, 40 μL) bounced off for free-fall heights from 5 cm to ∼13 m (Weber no. 36 to ∼2990) and displayed robust rain-repellency (Weber no. ∼4500), similar to that of a lotus leaf. Also, Bauhinia leaves survived pressurized water jets (Weber no. ∼4240). Nevertheless, underwater hydrophobicity has been persistent only for up to 3 h when submerged in 20 cm (∼1.96 kPa gauge pressure) deep water, while lotus leaves retained for >7 h. Such robust Bauhinia leaf's nanoplatelets and wax chemistries can be replicated onto glass/metals for preparing rain-repellent surfaces.
坚固的防雨表面在屋顶、太阳能板、挡风玻璃等方面很有用。在此,展示了树叶优异的防雨性和液滴弹跳特性。它们具有表面微凸起(约13μm、约8μm、约3μm),这些微凸起又由纳米片(约741nm、约59nm)组成,且具有约2.2的文泽尔粗糙度。通过将r纳入范奥丝-古德-乔杜里理论,估计树叶的表面能为9.47±0.03 mJ·m 。树叶的静态接触角为157±1°,滚落角为9±1°,接触角滞后为12±4°,在自然天气和实验室条件下老化长达186天期间这些角度保持不变。水滴(10μL、40μL)从5厘米至约13米的自由落体高度弹起(韦伯数从36至约2990),并表现出强大的防雨性(韦伯数约4500),类似于荷叶。此外,紫荆叶能承受加压水射流(韦伯数约4240)。然而,当浸入20厘米(约1.96 kPa表压)深的水中时,水下疏水性仅持续3小时,而荷叶能保持超过7小时。这种坚固的紫荆叶纳米片和蜡的化学性质可以复制到玻璃/金属上以制备防雨表面。