(86c) Generating Charged Liquid Droplets By Contact Electrification

Contact electrification is the phenomenon in which static charge is generated when two surfaces come into contact and are then separated. This phenomenon has been widely observed and investigated for contacts that involve two solid surfaces. Here, we showed that charge can also be generated when a liquid comes into contact with a solid surface via contact electrification. In particular, we found that when water droplets flowed down a solid (e.g., polymeric) surface under gravity, the droplets became charged. When a continuous flow of charged liquid was collected in a centralized location (e.g., a vessel), we found that a constant electric current was generated. Therefore, electricity can be generated directly by harvesting the gravitational energy of water (e.g., from sources such as rain or streams of water) through contact electrification. After optimizing the conditions of the system, we found that the efficiency of energy conversion (i.e., the amount of electrical energy generated divided by the amount of gravitational energy lost by the droplets) can reach up to around 3-4%. In addition, we found that the droplets generated have high electric potentials. Hence, contact electrification may be a simple, clean, and inexpensive way to generate charged liquid droplets.