Fully Wireless and Batteryless Localization and Physiological Motion Detection System for Point-of-care Biomedical Applications

Localization of wireless capsule endoscopes (WCE) is essential for advancement in the treatment of gastrointestinal (GI) tract diseases. Localization is also essential in biomedical applications such as detecting cancerous tissues, drug delivery, brain mapping, and robotic surgeries. Current localization systems are either battery-powered or require large coils for wireless power transfer, making them bulky and unfit for use in wearable or implantable applications. This paper proposes a fully battery-less localization system using wireless energy harvesting. Additionally, the system can be used for the detection of the rate of periodic physiological motions such as diaphragm motion during breathing. The proposed localization system uses ISM bands and transmits a locked sub-harmonic 13.56 MHz signal generated from the received 40.68 MHz radio frequency (RF) signal, eliminating the need for a power-hungry oscillator. The localizer has a small form factor of 17 mm × 12 mm × 0.2 mm and consumes an average power of 6 μW. Ex vivo measurements using the localizer inside the porcine intestine demonstrate a localization accuracy of less than 1 cm.