Photovoltaic (PV) and fully-integrated implantable CMOS ICs

Today, there is an ever-growing demand for compact, and energy autonomous, implantable biomedical sensors. These devices, which continuously collect in vivo physiological data, are imperative in the next generation patient monitoring systems. One of the fundamental challenges in their implementation, besides the obvious size constraints and the tissue-to-electronics biocompatibility impediments, is the efficient means to wirelessly deliver power to them. This work addresses this challenge by demonstrating an energy-autonomous and fully-integrated implantable sensor chip which takes advantage of the existing on-chip photodiodes of a standard CMOS process as photovoltaic (PV) energy-harvesting cells. This 2.5 mm × 2.5 mm chip is capable of harvesting [mu]W’s of power from the ambient light passing through the tissue and performing real-time sensing. This system is also MRI compatible as it includes no magnetic material and requires no RF coil or antennae. In this dissertation, the optical properties of tissue and the capabilities of the CMOS integrated PV cells are studied first. Next, the implementation of an implantable sensor using such PV devices is discussed. The sensor characterizing and the in vitro measurement results using this system, demonstrate the feasibility of monolithically integrated CMOS PV-driven implantable sensors. In addition, they offer an alternative method to create low-cost and mass-deployable energy autonomous ICs in biomedical applications and beyond.