NIR light-triggered bursting of double-emulsion drop (DED) for micro-droplets generation

Micro-droplets have significant applications in microbiologies, pharmaceuticals, cosmetics, and synthetic materials. Here, we present for the first time a near-infrared (NIR) light-triggered double-emulsion drop (DED) bursting method for generating a large number of micro-droplets in several micron. Under the irradiation of NIR light, the inner water phase of the DED containing a trace amount of Prussian blue (PB) rapidly heats up and evaporates rapidly to generate microbubbles due to the photothermal property of PB. By controlling the light intensity, the DED can inflate itself by coalescing these constant microbubbles to burst immediately and tear the middle oil phase to form a large number of micro-droplets. The performance of micro-droplets generated by NIR light-triggered DED bursting is investigated at different oil shell thickness (HO), oil phase viscosity (ηO) and oil type. HO and ηO are both key factors affecting the generation of micro-droplets. DED with lower HO and ηO can generate lower polydispersity and large quantity of micro-droplets by NIR-triggered DEDs bursting. The proportion of micro-droplets below 10 μm can reach up to 95%. Furthermore, camellia oil, as middle oil phase of DEDs, also can be used to generate lower polydispersity and large quantity of micro-droplets in several micron. The presented bursting method has a great potential to generate micro-droplets for micro/nano and biotechnology applications.