A wireless bladder volume monitoring system using a flexible capacitance-based sensor

A wireless sensor system has been prototyped to monitor bladder volume in a small animal. The capacitance-based sensor was laser-micromachined from a polyimide film to form an interdigitated finger structure, followed by a sputtering process to deposit aluminum thin film. The entire sensor was encapsulated with biocompatible and elastic polydimethylsiloxane (PDMS). A passive telemetry platform based on inductive coupling was realized to employ the sensor in vivo and a commercial wireless module was used for data communication in air. The entire system consists of a sensor implant, an external wearable unit and a base station. The system was tested with a small rodent model demonstrating the feasibility and identifying practical issues in implementation.