Triboelectric Nanogenerators Enable Multifunctional Ice Accretion, Melting, and Interfacial Fracture Detection

Triboelectric nanogenerators (TENGs) have significant potential to perform as sensors or compact electric power generators through the production of electrical charge during the frictional interactions between two dissimilar materials, such as liquids impacting solids. However, whether phase transitions generate a triboelectric response is not known. This study investigates the occurrence of triboelectrification during the water-ice phase transition using TENGs for real-time ice detection on critical engineering surfaces such as aircraft, wind turbine blades, and vehicles. TENGs are fabricated using aluminum electrodes and either polyethylene, silicone, or polytetrafluoroethylene as the dielectric. The freezing of water and the melting of ice are found to generate triboelectric current only during motion of the contact line, and the presence of ice can lessen additional charge transfer during continuous ice accretion. Further, ice type (rime versus glaze) can be differentiated during accretion by the initial transferred charge and how quickly the signal plateaus. It is observed that mechanical de-icing generates triboelectric charges that are proportional to the de-icing force, and this allows for the identification and quantification interfacial fracture mechanisms such as stress-controlled, toughness-controlled, and cavitation-controlled de-bonding. A prototype ice sensor is validated on a flying drone exposed to simulated rain under icing conditions, where it is able to detect both icing and de-icing in flight. The TENGs exhibited a signal-to-noise ratio as high as 83 dB, highlighting triboelectricity as a novel, real-time, and energy-efficient solution for ice detection and protection systems.