Sustainable Paper-Based NFC Tag for on-Field Humidity Sensing

The extreme weather conditions due to climate change are drastically calling for crop health supervision in agriculture via suitable technologies able to wirelessly, distributedly, and sustainably monitor relevant parameters. In this work we demonstrate a wireless eco-friendly capacitive humidity sensor, fabricated via dispense printing on biodegradable paper. It comprises an NFC antenna made of a biocompatible silver ink and an interdigitated electrode (IDE) sensor realized with a biodegradable carbon ink. The sensor response to humidity was evaluated in a climatic chamber, showing an R<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 0.92 and 0.98 and a sensitivity of 9.9 fF/% RH and 13 fF/% RH for increasing and decreasing RH values, respectively. The antenna was designed and characterized to resonate at the NFC frequency of 13.56 MHz. By being placed near a plant, this eco-friendly wireless device can estimate drought stress of the crop and support optimal water resource utilization. It also minimizes environmental impact, thereby paving the way for sustainable agricultural practices.