Photovoltaic high-throughput microfluidic platform for the mass-production of hybrid viscous microdroplets towards diverse applications

Scientists have been pursuing a compact, electrodeless microfluidic platform with a simple structure to realize the efficient cascading manipulations of serial aqueous microdroplets. In this study, we present a photovoltaic microfluidic platform to handle viscous Sodium-Alginate-doped aqueous microdroplets dispersed in a continuous surfactant-doped oil phase. Three kinds of optical response (Non-coalescence, Successful coalescence, and Bouncing back) are observed between adjacent microdroplets. Both the surfactant and SA concentrations are employed to optimize the laser-illumination intensity range of successful coalescence. We realized, that by simply applying focused-laser illumination, the sequential cascading of microfluidic manipulations including trapping, coalescence, mixing, and release of viscous aqueous microdroplets could be controlled in a reconfigurable, high-throughput manner. By properly adjusting the laser-illumination intensity, we can control the number of the microdroplets participating in the coalescence as well as the degree of the liquid mixing inside coalescent microdroplets, thus realizing the mass-production of hybrid viscous aqueous microdroplets. With this platform, we prepare Janus microparticles possessing magnetic and phosphorescent properties for assembling a magnetically driven displayer. Moreover, bioreactors are prepared with both immobilized yeast cells for effective fermentation and embedded magnetic nanoparticles for convenient recovery. Additionally, we generate, on this platform, chains of fluorescent double-emulsion microdroplets for optically encoding the information of the target microdroplet. The photovoltaic MHTE platform, with a simple chip design and good integrability with other LN-based photonic components, allows for an electrodeless, biocompatible manipulation of serial aqueous microdroplets with minimal temperature fluctuation, showing great potential in diverse fields including optics, MEMS, biotechnology and chemical sciences.