Investigation on Readout Strategy for Aqueous NH3 Sensor Developed by Additive Technology

Low-cost solutions for the detection of ammonia and its related compounds are of deep interest, due to several application contexts requiring suitable approaches for its detection, both as a direct product of industrial or biological processes, as well as a byproduct of complex reactions. This paper addresses the need of ammonia detection for the indirect estimation of phenylalanine, which is of interest in the context of Phenylketonuria disorder. The main idea behind the proposed approach is to exploit the ammonia produced by the enzymatic reaction phenylalanine-phenylalanine ammonia-lyase. The sensing methodology investigated through this paper is based on a chemo-capacitive readout strategy, implemented by a stack structure using interdigited electrodes and a functional layer of Yttria-Stabilized Zirconia. The sensor behavior is addressed, along with a dedicated signal processing allowing to retrieve a reliable information on the target media from the sensor output. The system shows a responsivity of 0.077 pF/μM, a resolution of 2.5 μM and an accuracy of 22.5 μM in the 3σ level.