Water–Responsive Porous Polydimethylsiloxane Triboelectric Nanogenerator With Complementary Optical Modulation and Droplet Sensing

Distributed sensing systems with reduced maintenance and enhanced multifunctionality are increasingly required for smart buildings enabled by the Internet of Things. Herein, a transmittance-shifting triboelectric nanogenerator (TS-TENG) providing complementary droplet-induced electrical sensing and water-responsive optical modulation is proposed. The device consists of porous polydimethylsiloxane (PDMS) on indium tin oxide glass, enabling reversible transparency regulation through water infiltration and release within the porous structure. The optical transmittance decreases from 84.80% in the transparent state to 46.67% after water infiltration, producing a hazy appearance. In parallel, droplet impacts are converted into electrical signals for real-time sensing, and stable output is maintained under continuous operation after optimization of the droplet-impact conditions. The transient electrical response enables rapid detection of droplet impacts, whereas the reversible transmittance change indicates sustained water infiltration within the porous layer. These mechanistically distinct but complementary responses are realized within a single porous PDMS-based device without requiring a separate optically active material, providing a dual-response platform for water-responsive sensing and optical wet-state indication.