Chemiresistive sensor for breath frequency and ammonia concentration in exhaled gas over a PVA/PANI/CC composite film

Abstract

The present study demonstrates the chemiresistive monitoring of respiratory frequency and ammonia gas in breath-out gases over a solution blended, electrically conducting, and humidity-responsive composite film of polyvinyl alcohol, polyaniline, and china clay (PVA/PANI/CC) over a commercial mask. The chemical structure, morphology, and relevant properties of the composite were investigated by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), a two probe method, and other suitable standard methods. The analytical response performance results reveal the synergistic evolution of electrical conductivity, and the humidity-responsive nature in the PVA/PANI/CC composite in the range of 5 to 95% RH along with promising sensing parameters, i.e., 0.09144 kΩ RH⁻¹ sensitivity, response time 6 s, recovery time 10 s, stability for 80 days, and V₂ flame retardant nature. Further, the resistance of the composite film coated on a commercial mask was measured after exposure to inhaled and exhaled human breath air and was further used to monitor the breath frequency and presence of ammonia concentration in breath-out gas to screen the kidney function. Further, a mechanism for humidity-mediated breath monitoring has been proposed based on the dissociative surface adsorption of water molecules and competitive adsorption of ammonia molecules, along with parameters and technical details.