SUB-$\mu\mathrm{W}$ Wireless Infrared Sensor with above-Threshold Measurement Function Based on a Bistable Micromechanical Switch

This work reports on the first ultra-low power infrared (IR) wireless sensor based on an IR micromechanical photoswitch (MP) and a microcontroller capable of quantifying the above-threshold input IR radiation and transmitting the measured value wirelessly. The entire sensor node remains asleep (standby power ∼811 nW) until awakened by the always-alert IR digitizer (i.e., the MP) upon exposure to targeted IR radiation. Unlike existing switch-based zero power sensors that only provide a binary output (i.e., indicate the presence of an IR source), the awakened sensor exploits a thermally-modulated electromechanical pull-in mechanism to measure the incident IR power using the same MP, the value of which is then transmitted wirelessly to a remote gateway. The prototype demonstrated here paves the way for maintenance-free coin battery-powered sensors for longterm and high-granularity remote deployment.