ZnO/MoS2-Based Enhanced Humidity Sensor Prototype With Android App Interface for Mobile Platform

Abstract

Humidity sensors have wide range of applications. In this paper, an inorganic hybrid thin film of molybdenum disulphide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )/zinc oxide (ZnO) was prepared as the sensing layer to develop a resistive humidity sensor containing aluminium electrodes on Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> substrate. The composite was analyzed using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction for their morphology and crystalline information. The sensor was exposed to various levels of relative humidity (RH) at room temperature and the response was found to be far better than pristine MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> or ZnO-based humidity sensors with the maximum response being 301 times at 85% RH. The results were reproducible with fast response and recovery, stable over a month with negligible hysteresis. A cost effective prototype was built on printed circuit board, and the data were acquired and transmitted to smartphone wirelessly using a Wi-Fi module (ESP 8266) interfaced to FRDM-KL25Z development platform. The Android application developed for the smartphone had the capability to switch ON/OFF the sensor device over Wi-Fi. Thus, our sensor device holds a great potential to develop an ultrasensitive, low power, low cost, and fast humidity sensor capable of indoor air quality monitoring in home automation systems (smart home).