Paper-Based Wearable Ammonia Gas Sensor Using Iron(III)-Added PEDOT:PSS

Paper electronics hold great potential that could replace conventional plastic electronics. Paper electronics are disposable and cost-effective, two distinct advantages for developing broadly accessible devices. However, the approach for functionalizing paper with electronic materials has not been sufficiently characterized from a chemical point of view. As a result, most paper-based electronic devices have an inferior electrical performance compared with plastic-based devices, which largely constrains their practical use. The design and fabrication of electronic materials on paper needs refinement to make paper electronics a valid, practical option. Here, we report a high-performance, paper-based, wearable ammonia sensor comprising composite poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and iron(III) compounds. We combined different printing and coating methods to develop the ammonia-sensitive, composite substance PEDOT:PSS:Fe³⁺ on paper. Our sensor achieves 10-times smaller size than the conventional sensor on Kapton film and high tolerance for humidity without impairing practical sensor response. We demonstrate the utility of our device toward wearable ammonia-sensing in a facial mask and a nasal filter; wireless battery-free monitoring of food spoilage; and wireless battery-free monitoring of the ammonia level in a paper diaper. All the comprising materials—cellulose paper, PEDOT:PSS, and iron(III) compounds—are abundant and eco-friendly, a further benefit for applications in which biological tissues or disposable wearable products are eventually discarded with the sensor attached. Our approach may open the door to advanced healthcare based on ubiquitous wearable sensing.