Electrical manipulation of liquid marbles for microreactions

Abstract

INTRODUCTION: Liquid-based reactions are essential for many applications, ranging from chemical synthesis to biomedical assays. Miniaturization of techniques for performing chemical and biological reactions has led to significant reduction of the volumes of the reaction reagents, and enhancement in the throughput of the resulting reactions. For instance, microfluidics has demonstrated feasible strategies to carry out microreactions, and to even integrate sequence of microreactions. While this has enabled multiple reactions and processing steps within the same microfluidic systems, these systems tend to be sophisticated and tool-intensive to build, and may not be suited for point-ofcare micro-reactions or tests for users without prior backgrounds in the tools. In this talk, I will introduce the use of larger droplets, coated by particles, as microreactors. METHODS: We will introduce devices that are incorporated with electrodes for electrically manipulating the liquid marbles. To demonstrate their feasibility to induce microreactions on demand, we will illustrate a few microreactions and biological assay of biological cells. RESULTS: The physics behind the electrical manipulation of liquid marbles will be elucidated, with different device geometries suited for different types of reactions illustrated[1, 2]. We will also discuss how the electrical manipulation will depend on the type of particles that coat the liquid droplets and the properties of the liquids inside the liquid marbles. These physico-chemical understanding allows us to extend the applicability of the approach to different reactions. In particular, we will outline how the liquid marbles containing different contents, including reactants, biological cells and assay components, can be actuated, coalesced and induced to react on demand[1, 3, 4]. In addition, we also demonstrate that this approach can avoid contamination of different reaction components[3]. CONCLUSIONS: Electrical manipulation of liquid marbles is versatile and robust, enabling the manipulation of nano- to microliters of liquids with devices that are simple to fabricate and free of contamination. Different types of microreactions and biological assays can be conveniently carried out within these liquid marble microreactors. Massive parallelization of the proof-of-concept electrically addressable devices will enable development of tools for automated conduction of microreactions and biological assays with great ease of operation. REFERENCES: [1] Z. Liu, X.Y. Fu, B.P. Binks, H.C. Shum, “Coalescence of electrically charged liquid marbles”, Soft Matter, 13 (2017) 119-124. [2] Z. Liu, X.Y. Fu, B.P. Binks, H.C. Shum, “Mechanical Compression to Characterize the Robustness of Liquid Marbles”, Langmuir, 31 (2015) 11236-11242. [3] X.Y. Fu, Y.G. Zhang, H. Yuan, B.P. Binks, H.C. Shum, “Controlled Actuation of Liquid Marbles on a Dielectric”, ACS Applied Materials & Interfaces, 10 (2018) 34822-34827. [4] Z. Liu, T. Yang, Y. Huang, Y. Liu, L. Chen, L. Deng, H.C. Shum, T. Kong, “Electrocontrolled Liquid Marbles for Rapid Miniaturized Organic Reactions”, Advanced Functional Materials, accepted (2019).