Due to the intrinsic lack of spatial order and self-supported shape, liquids are often incompatible with precision manufacturing/processing and are potentially limited for advanced functionality. Herein, an optothermal strategy is developed to fully command phase-separated liquids with unprecedented spatiotemporal addressability. Specifically, a laser is focused onto an Au film to create a hot spot that locally demixes a temperature-responsive solution to produce a single optothermal droplet. Spatial precision is assured by the well-defined thermal field and temporal accuracy guaranteed by the fast heating and response rate. Time-multiplexed laser foci are deployed to engineer the thermal landscape as desired, which in turn dictates the formation/dissolution, positioning, shaping, and dynamic reconfiguration of the phase-separated liquids. Further, laser foci are programmed to orchestrate the liquid patterns in a time-continuous manner to produce liquid animations on the microscale with high fidelity. While focused lasers are routinely used to manipulate solid particles or to microfabricate solid materials, the current strategy embraces the merits of liquids and features functional complexity in information encryption, payload transportation, and reaction localization. The strategy is further applicable in scenarios such as subcellular organization of biomolecular condensates and programmable modulation of non-equilibrium systems.
Keywords: coacervation; focused lasers; optothermal strategies; phase separation; programmable liquids.
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