Sensitivity-Enhanced $LC$ Pressure Sensor for Wireless Bladder Pressure Monitoring

This paper presents a sensitivity-enhanced wireless passive LC pressure sensor for monitoring bladder pressure, which can be minimally invasive implanted in the bladder or integrated to a commercial urinary catheter and avoid battery lifetime problem. The proposed sensor design and the theoretical model are useful to increase the pressure sensitivity of a typical air-sealed capacitive pressure sensor, particularly having a flexible diaphragm. The test results of an in vitro evaluation of the prototype LC pressure sensor show a pressure sensitivity of 6385 ppm/kPa (a pressure responsivity of 1.215 MHz/kPa) before encapsulation coating in air at room temperature, whereas 4175 ppm/kPa (0.627 MHz/kPa) and 2679 ppm/kPa (0.304 MHz/kPa) after coating with silicone rubber in air and in water operation, respectively. Finally, the feasibility of the developed sensor is investigated through an animal test and confirmed by comparing with the data of conventional cystometry.