Body-Heat Powered Biosensor Readout using Current-mode Relaxation Oscillators

This paper presents a multi-sensor biochemical measurement IC that can be powered using thermoelectric energy harvesting, such as from body heat. A current-mode relaxation oscillator (RxO) readout approach is used to enable ultra-low-power sensor front-end circuits. A system-on-chip with integrated energy harvester was implemented in a 0.18µm CMOS process as a proof-of-concept. The fabricated IC is used to demonstrate pH and glucose measurement using off-chip sensors. An RxO using a V-to-I input converter demonstrating pH measurement consumes 2.2µW at maximum, where the RxO consumes 0.7µW. Measured linearity of the readout circuits demonstrate R²>0.999. Glucose measurement is also demonstrated using an on-chip potentiostat circuit while powering from body heat using an thermoelectric generator on the skin surface.