26.5 A 20µW Heartbeat Detection System-on-Chip Powered by Human Body Heat for Self-Sustaining Wearable Healthcare

Wearable devices are expanding beyond consumer and entertainment applications, including continuous monitoring of vital signs for medical diagnostics, due to extended ambulatory measurement capabilities compared to fixed clinical environments. Continuous long-term use is difficult for battery-powered devices in a wearable form-factor, whereas ambient energy harvesting promises power autonomy to enable indefinite lifetime for true battery-less devices. However, accurate vitals measurement under real-world motion conditions is energy intensive [1], making it difficult to provide reliable and medically relevant data using typical micro-watt power levels available from energy harvesting.