Oil/Water Microreactor with a Core–Shell Wetting State on a SOB/OL-SHB/HL Multilevel Patterned Surface

Abstract

Droplet-based microfluidics, which manipulate mini-discrete droplets on surfaces to accomplish various chromogenic/fluorescence reaction-based detections, are promising for microminiaturization of analysis systems. However, rapid droplet evaporation in unsaturated surroundings is a complex problem. In this study, we proposed an ingenious concept of generating an oil/water microreactor on a superoleophobic/oleophilic-superhydrophobic/hydrophilic (SOB/OL-SHB/HL) multilevel patterned surface. A dual droplet with a nonvolatile liquid packing layer and a volatile droplet core was formed on the surface, achieving overt evaporation attenuation of the droplet core. The wettabilities of the SOB/OL-SHB/HL surface were first investigated. In addition, due to their outstanding configurability, oil/water microreactors with different pattern shapes, diverse compositions, and scale-up array configurations were obtained in a simple way. Due to the overt evaporation attenuation, the storage times of the reactants and products were markedly prolonged. Finally, as proofs of concept, oil/water microreactors were successfully applied to detect the target ion and to construct a droplet-based pH detector. The proposed oil/water microreactor on the SOB/OL-SHB/HL surface with distinct precision, flexibility, and high throughput is important to the development of high-performance microfluidic chips used in diagnosis, environment monitoring, chemical analysis, and particle synthesis.