A water droplet-powered sensor based on charge transfer to a flow-through front surface electrode

A water droplet sensor based on a flow-through front surface electrode is demonstrated. It is shown that a triboelectric nanogenerator based on a metal-dielectric junction can be utilized to construct simple, self-powered water drop counters that require only a minimum of electronical components. Every water drop generates a flash in a light emitting diode, which is detected by a silicon photodetector located some distance away. Different transducer designs are investigated, either in the form of flat tilted surfaces or polymer-covered metal wires, with the former found to provide the largest charge transfer while the latter is less sensitive to positional stability. It is also demonstrated that the sensor could be utilized to monitor the state of the magnetic field-controlled turbidity of a solution without any additional electronics, thus making a minimalistic design feasible.