Water Droplets Driven by the Giant Surface Potential of Organic Films

Controlling droplet motion on solid surfaces presents significant challenges in chemistry, physics, and materials science, especially for potential applications in "lab-on-a-chip" technologies. Traditional methods, such as using electric fields produced by electrodes, often inadequately manage complex droplet motion. Here we show a novel approach utilizing giant surface potentials (GSPs) generated through customizable photopatterning during vacuum deposition. Water droplets move spontaneously due to the potential difference between the GSP surface and the surface where the droplet comes into contact, which has a reduced potential. Our study not only enhances droplet control but also improves the photostability of the surface potential. We identify the optimal conditions for GSP generation, achieved under vacuum-deposition conditions conducive to maximum enthalpy relaxation, and demonstrate its potential for creating customizable, complex droplet flow channels. These advances offer significant promise for microfluidic devices, medical diagnostics, chemical synthesis, and energy harvesting applications.