Title: Directed Pinning of Moving Water Droplets on Photoresponsive Liquid Crystal Mats

Author: Yuyun Liu, Chongyu Zhu, Yong Zhao, Xin Qing, Feng Wang, Daosheng Deng, Jia Wei, Yanlei Yu*

Journal: Adv. Mater. Interfaces 2019, 6(21), 1901158

Abstract:

Compared to conventional continuous-flow liquid manipulation, the direct control of liquid droplets on an open surface prevents the potential cross contamination during liquid transfer, which is advantageous for biological microliquids. However, the fabrication techniques of smart surfaces and the fast manipulation of droplets remotely remain difficult, limiting its practical application. Herein, large-scaled photoresponsive superhydrophobic mats fabricated by the electrospinning of linear liquid crystal polymer are presented. Upon the alternated irradiation of UV-vis light, these mats exhibit significant, fast, and reversible change of adhesion, while their surfaces maintain the superhydrophobicity. Therefore, the water droplets can be pinned at any directed point on the mat surface after the fast superhydrophobic adhesion switch by the remote control of light. It is expected that the active manipulation of discrete droplets on an open surface through these photoresponsive mats provides a new concept for microdroplet manipulation,allowing for minimal reactions among biological samples.

Fulltext Link: https://onlinelibrary.wiley.com/doi/full/10.1002/admi.201901158

Based on the photoresponsive LLCP with high molecular weight, we construct photoresponsive superhydrophobic mats in a large scale by electrospinning and demonstrate the fast switch of superhydrophobic adhesion of the mats controlled by light. The rapid and large changes of adhesive force (AF) and the surface free energy on the mats arise from the polarity change and the reorientation of photoisomerized azobenzene mesogens on the surface of nanofibers. Possessing this unique photoresponsive property, these mats allow the pinning of the water droplets at any directed point on the surface after UV light irradiation for 2 s. This photoresponsive LLCP mat will be an ideal candidate to achieve the active manipulation of discrete droplets on an open surface, which will enable the further extension of minimum bioreaction for diagnostics and drug screening.