Directional Droplet Propulsion on Gradient Boron Nitride Nanosheet Grid Surface Lubricated with a Vapor Film below the Leidenfrost Temperature

作者：Wang, Yu; Wang, Ruixiao; Zhou, Yanjiao; Huang, Zhenguo; Wang, Jingming^*; Jiang, Lei

来源：ACS Nano, 2018, 12(12): 11995-12003.

DOI：10.1021/acsnano.8b04039

• boron nitride
• directional droplet propulsion
• structural hydrophobicity
• intrinsic hydrophilicity
• Leidenfrost temperature

Controlled propulsion of liquid droplets on a solid surface offers important applications in various fields, including fog harvesting, heat transfer, microfluidics, and microdevice technologies. The propulsion of the liquid droplet is realized only if the driven force exceeds the resistance force. Sometimes the directional propulsion of droplets only takes place at the Leidenfrost state to achieve enough lubrication for a vapor cushion. The thick vapor cushions levitate liquid droplets to reduce resistance force. However, it is still challenging to reduce the vapor cushion thickness and simultaneously realize the directional droplet's motion, especially below the Leidenfrost temperature. Here, a structurally hydrophobic boron nitride nanosheet (BNNS) grid surface was constructed with a two-direction topographical gradient, i.e., the perpendicular altitude gradient and the horizontal density gradient. The polar nature of the B-N bonds results in intrinsic hydrophilicity of the boron nitride layer, which increases the Leidenfrost point and facilitates wetting even at high temperature. Much thinner vapor-lubricating layers are competent in the droplet's directional motion below the Leidenfrost temperature of the BNNS grid surface because the air gap trapped within boron nitride nanosheet grids acts as a part of the lubrication layer.

• 出版日期2018-12
• 单位江西理工大学; 中国科学院理化技术研究所; 北京航空航天大学