Underwater Ionic Current Signal Sensing and Information Transmission by Contact-Induced Charge Transfer

Underwater ionic current signal sensing shows great potential for electric-field-sensing-based target detection, information transmission and communication. Nevertheless, it is still a challenging task. Herein, a self-powered underwater ionic current signal sensing system using contact-induced charge transfer is presented. The system mainly consists of a working electrode, a metal sheet and a sensing electrode that is immersed in electrolyte solution. Upon touching the working electrode with a metal sheet with a different work function, charge transfer occurs on the interface, and a corresponding ionic current is induced. The generated ionic current can be detected with the sensing electrode far away from the working electrode. It was found that the magnitude and direction of the generated ionic current are determined by the contact potential difference (CPD) between the working electrode and the contacting metal sheet. Additionally, the effects of water temperature, the ionic concentration of the electrolyte solution, electrode surface area and hydrostatic pressure are systematically investigated. The detected signal magnitude decreased with an increase in the distance between the working electrode and the sensing electrode. A proof-of-concept demonstration of underwater information transmission via Morse code with this method was successfully achieved.