Self-sustained electric field-driven off-grid platform for on-demand microdroplet charging and programmable...

Power independence and system simplicity are paramount for robust droplet manipulation in decentralized applications, including point-of-care diagnostics and wearable biosensors. However, conventional active microfluidics for droplet manipulation are often bottlenecked by the requirement for high-voltage power supplies, intricate electrode networks, or magnetic additives that escalate system complexity and restrict portability. Here, we report a self-sustained electric-field-based electrophoretic platform (SELF-EP) that achieves autonomous droplet charging and sophisticated manipulation, entirely eliminating the need for external power sources. This is enabled by a specialized SELF emitter engineered to retain quasi-permanent surface charges, providing a continuous and stable SELF. Rather than direct charge injection, SELF drives electrostatic induction, drawing charges from ground to induce a net charge on droplets. Through integrated theoretical modeling and experimental validation, we demonstrate that the SELF-EP allows for deterministic control of droplet charge and supports on-demand droplet manipulation with various spatial configurations. Notably, we show parallelized control of multiple droplets and realize complex, programmable functions such as self-alignment and routing via precise spatial patterning of surface charges. Our SELF-EP paradigm bypasses the need for active electronics, offering a minimalist yet multifunctional strategy that significantly expands the boundaries of autonomous microfluidic and biomedical technologies.