UC Berkeley

Pressure is one of the most frequent and important parameters utilized in many applications to provide critical information about the operation of a system as well as a potential mechanical energy source. Among various pressure-related devices, very few function in harsh environment which includes high temperature, high pressure, highly corrosive, or biofouling conditions. In the first part of this dissertation, a high temperature pressure sensor with a novel concentric ring-circle-shape design is proposed specifically for the geothermal applications with detailed modeling, fabrication, and characterization results. A concentrically matched ring-circular capacitance pressure sensor design is proposed to tackle the common mode noise problem of km-long cables in geothermal wells. Furthermore, to provide a high temperature and corrosive environment survivability, silicon carbide is utilized as it has superior material properties as compared to silicon in harsh environments. Experimentally, it was shown that the novel design can provide differential capacitance output at temperatures of 180℃ and capacitances ranging between 0.14 pF to 1.45 pF were observed from a sensor designed to operate under 1 MPa. In the second part of this dissertation, an energy harvester application is proposed to make the use of pressure fluctuations within the lateral ventricles of the brain which is a biofouling environment. This time, a concentric ring-circular design is utilized to convert the mechanical pressure fluctuations to electrical energy efficiently. The harvesters were fabricated using aluminum nitride as the piezoelectric material and the increase in efficiency of the proposed design was shown as characterized by both in-air and underwater tests. A 3D-printed lateral ventricle mockup setup was used to mimic the operation of the harvester in lateral ventricles and the harvester with a diameter of 2.5 mm generated a power of 0.62 nW. Moreover, considering the potential issues in deployment and mounting, a flexible harvester was developed using PVDF and PET materials and under water characterization the harvester with 3 mm diameter resulted in power of 1.75 nW.