Polyaniline/Poly(vinyl alcohol) Conductive Hydrogel for a Chemiresistive Ultrasensitive Ammonia Gas Sensor
Leimapokpam Sophia Devi, Thomas T. Daniel, Roy Paily, Ashok Kumar Dasmahapatra
Abstract
Printing technology is an emerging microfabrication technique that is being explored as a potential alternative to traditional semiconductor technology. This innovative approach allows for high precision, ease of fabrication, integration of multiple incompatible materials, and scalability, leading to the production of low-cost and high-performance devices. Herein, we present the fabrication and investigation of a chemiresistive sensor utilizing micro girder (μG) printing technology employing a repetitive freeze–thaw (FT)-cycled polyaniline/poly(vinyl alcohol) (PANI/PVA) hydrogel as the sensing material for the detection of ammonia (NH 3 ) gas down to 100 ppm at room temperature. The sensor shows an improved sensitivity of 94.7% for detecting 100 ppm of NH 3 with a limit of detection of 1 ppm. The repetitive FT cycles promote the formation of well-defined microstructures of the hydrogels, which has been shown by detailed structural and morphological analyses. This hydrogel-based chemiresistive sensor demonstrated a good response to NH 3 gas by monitoring changes in resistance, offering a cost-effective and practical alternative for NH 3 detection. The sensor exhibited high sensitivity to NH 3 with rapid response and recovery times of 25 and 10 s, respectively, making it suitable for real-time applications. Additionally, the study explored the hydrogel sensor’s cross-sensitivity to NH 3, nitrogen dioxide (NO 2 ), and carbon dioxide (CO 2 ). The sensitivity of the sensor toward some of the breath volatile organic compounds is also analyzed. The sensor’s behavior is found to adhere to the Langmuir adsorption/desorption model, further confirming its efficacy in gas detection. The excellent sensing ability with a high cross-sensitivity of the developed sensor is attributed to the formation of well-developed cross-linked network structures during FT cycles. The stability of hydrogel-based sensors over a 3-month period further supports their potential for practical deployment in various environmental and healthcare monitoring scenarios, aiming to provide a straightforward strategy for detecting exhaled breath ammonia.