Visualisation of charge dynamics when water droplets move off a hydrophobic surface

The Kelvin water drop generator is often used for educational purposes to visualise how charge is transferred when water drops separate from a solid. Here, we discuss an alternative and simpler setup, which allows one to visualise the charge transfer that occurs when water drops move off a hydrophobic polymer. One can visualise the charge transfer directly as light pulses from a light emitting diode, or monitor the current pulses generated by the water drops. Further investigation of the current pulses provides information about how single water droplets or fluctuating streams move down the incline.