Full-LIG wireless batteryless flexible sensor for the detection of triethylamine

Low-cost detection and quantitative measurement of volatile compounds are crucial in preserving the quality and integrity of food in mass volumes. A packaging-compatible wireless sensing and batteryless device can be entirely done of laser-induced graphene (LIG) which does not require additional conductors. Here, the proposed device is a flexible and fully integrated 868-MHz antenna and interdigital capacitor made by variable lasing parameters to simultaneously maximize the radiation performance and dump the RF-induced currents on the sensing device. The geometrical integration among the two devices is deeply investigated to reduce the parasitic capacitances that hinder the stability and accuracy of the measurement. The resulting device has the size of a credit card and can be read from up to 1.6 m through a standard UHF radio frequency identification (RFID) protocol. The sensing capabilities are tested by coating the capacitor with a chemical interactive material (CIM) (PEGDA) suitable to react to triethylamine compounds. Application of standard machine learning techniques permits to identify different concentrations (from 10% to 45%) of amine in a controlled environment with an RMSE≊ 5 and R2 =0.8.