Self-powered wireless plant health monitoring system detects circadian rhythm using sap-activated battery

A wireless plant health monitoring system composed of a self-powered wireless sensor and a receiver has been developed that detects a circadian rhythm related to sap flow including soil moisture conditions. The sensor, which has a sap-activated battery that has an iron nail with a diameter of 1 mm and an intermittent-power-supply circuit that performs power-gating operation with boosted voltage and reduces the leakage current to 0.1 nA, makes it possible to perform a sensing operation. We fabricated a prototype system and verified that the intervals between the received signals have a circadian rhythm while they gradually increased.