Minimalistic, disposable wireless electrochemical sensors: Integrating self-powered amperometry with direct inductive coupling

Point-of-care (PoC) biomolecular sensing enables rapid diagnosis and prognosis to significantly improve medical accessibility. Wireless electrochemical sensing strategies typically use dedicated RFID or Bluetooth chips for wireless transmission along with a microcontroller and potentiostat to convert chemical signals into electrical outputs. However, integrating chips and multiple active components into a sensor limits its miniaturization, power efficiency, and usage in disposable applications. We therefore propose a minimalistic yet sensitive and efficient sensor design using only one active component: an LED. The LED, paired with a photoresistor, converts currents from analyte concentrations into resistive changes, which are directly transmitted via inductive coupling. This pairing further functions as a buffer, isolating the electrochemical cell from the inductive link for stable wireless transmission. LED and electrochemical cell power is derived from a galvanic cell consisting of a pair of electrodes activated upon contact with bodily fluids. The integrated sensor was characterized with H₂O₂ measurement and incorporated into a diaper to demonstrate usability by measuring uric acid in artificial urine. The proposed approach to sensor design enables battery-free amperometry to be integrated with chip-free wireless data transmission, a promising step towards cost-effective and disposable electrochemical sensing.