Ingestible electronics without batteries : power and communication for gastroresident devices

Abstract

In this thesis, I introduce a novel ingestible electronic device designed to reside inside the stomach for weeks or longer with both wireless communication and wireless powering capabilities. The device is powered by a transmitter outside of the body via wireless power transfer through 5 to 6 cm of tissue, while keeping under specific absorption of radiation limits. Electromagnetic theory and microwave simulations identified the optimal region of operation for transmitting power through tissue as around 1 GHz. Small loop antennas fabricated to fit onto a circuit board the size of a pill capsule exhibited power transfer efficiencies of around -45 dB when tested ex vivo in pig stomach tissue. Choice of electronic components for rectification, sensing, and wireless communication are also discussed, as well as electrical and material characterization of an encapsulated device, to show that an end-to-end wireless ingestible electronic device is feasible for gastroresident applications.