A Flexible Underwater Pressure Sensor Array for Articial Lateral Line Applications

This thesis develops a flexible elastomer-based underwater pressure sensor array. When mounted onto the hull of an aquatic vehicle, the array enables obstacle detection, identification and tracking, and can help the vehicle reduce its hydrodynamic drag by providing information about the surrounding flow. This thesis begins with the development of a carbon black-PDMS elastomer material set. Using the material set, a 4-point-probe resistive strain gauge is developed and combined with a pressure-concentrating PDMS diaphragm to create the MEMS-based pressure sensors. A one-dimensional array of 4 sensors is fabricated, and the dynamic response of the sensors is characterized and modelled. Based on the model, the operating conditions required for a linear sensor response are determined. This thesis ends with proof-of-concept underwater object and wave detection experiments demonstrating that the sensor can function as an artificial lateral line. The sensors exhibit a 1.38 · 10−3 fractional resistance change per 100 pascals, which yields a maximum pressure resolution of 1.5 pascals for a power consumption of 10 μW per sensor, ignoring the power dissipated by the amplification circuitry and parasitic resistances. Each sensor is capable of transducing up to a 1 kPa pressure differential across its diaphragm, though the sensor may respond to signals of this amplitude at arbitrary underwater depth due to the use of a pressure equilibration scheme. The overall array has a 15 mm spatial resolution. An upper bound for the bandwidth of the diaphragms is calculated to be 940 Hz, ignoring viscous damping due to air, water, and the PDMS. Additionally, sensor operation while mounted to a hull with a 0.5 m radius of curvature is demonstrated. Thesis Supervisor: Jeffrey H. Lang Title: Professor of Electrical Engineering and Computer Science 4 A Flexible Underwater Pressure Sensing Array