Self-Powered, Electrochemical Carbon Nanotube Pressure Sensors for Wave Monitoring

Underwater pressure sensors with high sensitivity over a broad pressure range are urgently required for the collection of valuable data on pressure changes associated with various wave motions. Here, a class of carbon-nanotube-based pressure sensors, which can be directly used in oceans without packaging, is reported. They use salt water as an electrolyte for electrochemically converting mechanical hydraulic energy into electrical energy and generating electrical signals in response to pressure changes in seawater. They can sense wave amplitudes from 1 mm (i.e., 10 Pa) to 30 m, which covers the range of almost all wave motions, and provide high stability during cycling in seawater. Also, they are self-powered and provide harvested gravimetric energy that is six orders of magnitude higher than that for commercial piezoelectric sensors for frequencies below 2 Hz (the range within most wave motion occurs), which has not been achieved before. These self-powered sensors operate from 4 to 60 degrees C and in direct contact with salt water having a wide range of salinities (from 0.1 to 5 mol L-1). Importantly, the unique electrochemical mechanism provides a new pressure sensing strategy to address the challenges in realizing high precision, low-frequency pressure measurements, and a broad detection range.