Light control of droplets on photo-induced charged surfaces

Fang Wang; Meijin Liu; Cong Liu; Chao Huang; Lidong Zhang; Anyang Cui; Zhigao Hu; Xuemin Du

doi:10.1093/nsr/nwac164

Light control of droplets on photo-induced charged surfaces

Natl Sci Rev. 2022 Aug 17;10(1):nwac164. doi: 10.1093/nsr/nwac164. eCollection 2023 Jan.

Authors

Fang Wang¹, Meijin Liu¹, Cong Liu^{1

2}, Chao Huang¹, Lidong Zhang³, Anyang Cui⁴, Zhigao Hu⁴, Xuemin Du¹

Affiliations

¹ Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
² University of Chinese Academy of Sciences, Beijing 100049, China.
³ Department of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China.
⁴ Technical Center for Multifunctional Magneto-Optical Spectroscopy (Shanghai), Engineering Research Center of Nanophotonics and Advanced Instrument (Ministry of Education), Department of Physics, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China.

Abstract

The manipulation of droplets plays a vital role in fundamental research and practical applications, from chemical reactions to bioanalysis. As an intriguing and active format, light control of droplets, typically induced by photochemistry, photomechanics, light-induced Marangoni effects or light-induced electric fields, enables remote and contactless control with remarkable spatial and temporal accuracy. However, current light control of droplets suffers from poor performance and limited reliability. Here we develop a new superamphiphobic material that integrates the dual merits of light and electric field by rationally preparing liquid metal particles/poly(vinylidene fluoride-trifluoroethylene) polymer composites with photo-induced charge generation capability in real time, enabling light control of droplets on the basis of photo-induced dielectrophoretic force. We demonstrate that this photo-induced charged surface (PICS) imparts a new paradigm for controllable droplet motion, including high average velocity (∼35.9 mm s^-1), unlimited distance, multimode motions (e.g. forward, backward and rotation) and single-to-multiple droplet manipulation, which are otherwise unachievable in conventional strategies. We further extend light control of droplets to robotic and bio-applications, including transporting a solid cargo in a closed tube, crossing a tiny tunnel, avoiding obstacles, sensing the changing environment via naked-eye color shift, preparing hydrogel beads, transporting living cells and reliable biosensing. Our PICS not only provides insight into the development of new smart interface materials and microfluidics, but also brings new possibilities for chemical and biomedical applications.

Keywords: droplet manipulation; ferroelectric; light control; liquid metal; smart surface.