Preliminary Analysis on a Paper-based Ammonia Sensor for Future Food Smart Packaging

Here, we report a preliminary analysis on the manufacturing and testing of a low-cost and eco-friendly paper-based gas sensors realized with Aerosol Jet Printing (AJP) and Flash Lamp Annealing (FLA). The hygroscopic properties of paper make it possible to detect the presence of water-soluble gases in an environment provided with a relative humidity (RH) above a given threshold $(\text{RH} > 75\%)$ . This aspect allows the usage of such technology in the realization of a future food smart packaging detecting the presence of a malevolent gas like ammonia in food. Carbon interdigitated electrodes were printed and sintered on chromatographic paper, obtaining a mean resistance value of to $(231\pm 20)\ \mathrm{k} \Omega$ and $(249\pm 28)\ \mathrm{k} \Omega$ for the left and the right electrode respectively. The sensors were tested at different relative humidity (RH) values (75, 80, 90, 100%), and once stabilized they were tested with different ammonia concentrations (3, 6, 9 and 12 ppm). A proportional decrease was evidenced in increasing RH and ammonia concentration. Considering the baseline at a constant value of $\text{RH} =75\%$ , the sensors showed a resistance decrease of 15% in presence of the lowest concentration of 3 ppm.