Highly sensitive ammonia sensor based on a PMMA/PANI microwire structure

In this paper, a highly sensitive ammonia (NH 3 ) sensor based on a polymethyl methacrylate/polyaniline (PMMA/PANI) microwire structure is designed and implemented. First, a micron-sized PMMA microwire was fabricated and connected with two tapered single-mode fibers to form a coupling structure; thus, the Mach–Zehnder (MZ) interference was successfully excited due to the good light conductivity of the PMMA. It was demonstrated that the coupling structure behaved with a high refractive index detection sensitivity of 3044 nm/RIU. To make it sensitive to NH 3 , the PANI was selected to mix with PMMA and then formed a micron-level PMMA/PANI fiber. The experimental results showed that the PMMA/PANI fiber can selectively sense NH 3 with a high sensitivity of 65.3 pm/ppm. This proposed NH 3 sensor not only solves the problem of sensitive film shedding, but also possesses the advantages of good integration, high sensitivity, good selectivity, and short response time.