Title: Manipulating Small Water Droplets on A Photo-switchable Mat of Fluorinated Linear Liquid Crystal Polymers

Author: Xiao Zhang, Lang Qin, Yuyun Liu, Jia Wei, Yanlei Yu*

Journal: Giant, 2020, 2, 100019

Abstract:

Manipulating small water droplets on an intelligent surface with tunable superhydrophobic adhesion has attracted considerable interests because of potential applications ranging from no-loss transfer to surface chemistry but remains challenging. Herein, we present a strategy to manipulate the small water droplet on a photo-switchable mat, which is fabricated by a fluorinated linear liquid crystal polymer via electrospinning. The electrospun mat with hierarchical microstructures exhibits fast and reversible superhydrophobic adhesion change, and still remains the superhydrophobicity after pinning and removing of the water droplets for several times. Diverse erasable and rewritable arrays on the vertically placed mat are formed by pinning the small water droplets to any high adhesive position after localized light irradiation. Moreover, after evaporation of the water droplets containing aggregation-induced emission materials, the mat exhibits bright fluorescence upon faint UV irradiation to indicate the trace with the same pattern as the original droplets. Such photo-switchable superhydrophobic mats would provide an open tunable surface for microdroplets manipulation.

Fulltext Link: https://www.sciencedirect.com/science/article/pii/S2666542520300229?via%3Dihub

In this paper, fluorinated linear liquid crystal polymer (LLCP) is prepared into a light-controlled superhydrophobic mat with hierarchical microstructure by electrospinning technology. The electrospun mat is super-hydrophobic due to the hierarchical structure generated by the nanofibers on the surface. Because of the alteration of surface free energy aroused by reversible trans-cis isomerization of the azobenzene, the electrospun mat can also change super-hydrophobic adhesion within a few seconds. Since fluorination is an effective strategy to lower the surface energy, manipulating the microscale water droplet (≤ 4 μL) has been implemented. Besides, through pre-adhering micron-level water droplets with water-soluble AIE on the "LC" array, after water evaporates, the residual colorless AIE compound will emit bright fluorescence under the excitation of ultraviolet light, which further demonstrates the application in anti-counterfeiting technology.