I. Introduction
Recent advances in low-power electronics have paved the way for a wide range of wearable and implantable biomedical devices for health monitoring and fitness applications. Integration of such millimeter-scale devices on biocompatible platforms shows great potentials for real-time biochemical sensing [1]–[6]. Many personalized monitoring biodevices are designed to perform multiple tasks, such as on-demand wake-up, multiplexed sensing, data processing, and wireless data transmission. These power-demanding operations are performed continuously or periodically over long durations, which set challenging requirements for the energy sources and the overall power efficiency of the system [7].