Optical droplets sorting assisted by superhydrophobic surface with hydrophilic patterns

摘要

The droplets sorting in the well-defined microdroplets array is significantly important in fields including biomedicine, pharmacy, primary diagnosis and chemosynthesis due to its pivotal role in the follow-up analysis, collection and other applications. Recently, the light control of droplets using the interactions between light and fluids allows for the contactless droplets sorting with prominent features. Among the interactions, the photothermal effect has shown significant potential. In this work, we investigated the photothermal effect-induced interface dynamics of neighboring droplets in the microdroplets array on the superhydrophobic surface with hydrophilic patterns. It was found that the irradiated droplet was rapidly collapsed by the photothermal effect-induced evaporation-condensation-extension while the adjacent droplet's outboard triple-phase contact line was gradually extended and showed more significant extension due to the limited vapor condensation in the space between the droplets. The light induced interface behaviors of neighboring droplets under different droplet gaps and laser powers were also analyzed. Based on the findings, a proof of concept of the droplets sorting platform manipulated by the light was demonstrated. With the assistance of the hydrophilic patterns on the superhydrophobic surface and the laser heating, the target droplet reached the hydrophilic patterns could spontaneously move to the designated position via the imposed asymmetrical surface tension, realizing the droplets sorting. The results indicated that the light-induced interface migration of the droplets in the micro droplets array could sort the target droplets with high yields and remarkable simplicity and show promising potential in many biochemical analysis applications but not limited. (C) 2019 Elsevier Ltd. All rights reserved.