Droplet Triboelectrification on Liquid‐Like Polymer Brushes

Abstract Solid–liquid triboelectric nanogenerators offer promising energy harvesting and sensing capabilities, yet the role of wettability parameters in governing triboelectrification remains underexplored. Here, the triboelectrification of water droplets on liquid‐like polymer brush‐coated surfaces with varying chemical compositions and contact angle hysteresis is explored. Triboelectrification signals are measured as droplets slide across spatially distributed electrodes; high‐speed imaging correlates the current output with droplet motion. By varying droplet velocity, travel distance, and electrode distribution, an optimal balance is identified for maximizing signal output, with measured currents ranging from ≈2–21 nA for polyethylene glycol, polydimethylsiloxane, and perfluoropolyether brush‐coated surfaces. The effect of changing the contact area is also examined by compressing and decompressing droplets between two polymer brush‐coated surfaces, where the contact area is expanded up to 10 times. This enables precise control over the rate of contact area change, which is found to exhibit the strongest influence on triboelectrification signals, yielding current peaks exceeding 300 nA. As a potential application, electrode patterning is combined with wettability channels to enable mechanical pressure sensing, where increasing pressure triggers contact with multiple electrodes, generating current signals ≈20 nA. This work highlights the role of interfacial dynamics and surface chemistry in shaping triboelectric output.