Giant surface potentials in organic films enable electrode-free self-driven water droplets

Abstract

Vacuum-deposited organic molecular films can generate giant surface potentials (GSPs) through spontaneous molecular orientation. Here we show that these GSPs can directly drive autonomous water droplet motion via dielectrophoretic forces, enabling high-speed transport of up to ∼15 cm s⁻¹ without electrodes or externally introduced charges. The motion originates from an electric field gradient formed between the GSP region and the potential-relaxed area beneath the droplet. Using photopatterning of photochromic diarylethene, droplet trajectories can be spatially programmed. We further demonstrate that the long-standing issue of GSP photostability can be overcome using highly insulating molecular materials. This GSP-driven mechanism provides a new strategy for electrode-free droplet manipulation and opens opportunities in microfluidics, diagnostics, chemical synthesis, and energy harvesting.