This study proposes and develops tin (IV)-oxide (SnO2)-based H2S microsensors with different geometrically designed embedded micro-heaters. The proposed micro-heaters affect the operating temperature of the H2S sensors, and the micro-heater with a rectangular mesh pattern exhibits superior heating performance at a relatively low operating voltage (3–4 V) compared to those with line (5–7 V) and rectangular patterns (3–5 V). Moreover, utilizing a micro-heater with a rectangular mesh pattern, the fabricated SnO2-based H2S microsensor was driven at a low operating voltage and offered good detection capability at a low H2S concentration (0–10 ppm), with a quick response (<51 s) and recovery time (<101 s). 

Infrared detectors are devices that convert thermal energy into electrical energy. There are mainly two types of infrared detectors which can be classified based on the presence of a cooling system. Thermopile is a highly promising type of infrared detector due to the fact that it is uncooled and does not require periodical infrared source to function properly. As a thermal type of infrared detector, it is capable of continuously generating an electromotive force (emf) from infrared radiation without any frequency restrictions. This makes it an ideal choice for various applications that require reliable, continuous and uncooled infrared detection capabilities. 

The Fabry-Perot filter, also known as an etalon, consists of two parallel reflecting surfaces that form an optical cavity. The surfaces are typically thin reflectors that are highly reflective and face each other, creating a resonance cavity where only optical waves that are in resonance with it can pass through. A Distributed Bragg Reflector (DBR) is a structure utilized in optical filter. This structure is created by alternating multiple layers of materials with varying refractive indices or by periodically varying certain characteristics of the dielectric waveguide, resulting in a periodic variation in the effective refractive index in the filter 

Colorimetric sensor that uses a gasochromic material, whose light transmittance changes according to hydrogen adsorption, does not require a direct flow of electricity into the sensor; therefore, there is no risk of hydrogen explosion due to electric discharge, which means that this method can solve the drawbacks of existing sensors. With the gasochromic method, hydrogen leaks can be detected remotely through light transmitted from the sensing material to the optical spectrometer, or immediately to the human eye without optical spectrometer due to the color change in visible light wavelengths. Remote hydrogen detection is possible, and immediate detection is possible with the human eye without a signal converter in the sensor circuit due to the color change in the visible wavelength. The advantage of the gaschromic sensor is that it fundamentally blocks the possibility of explosion due to discharge because only light is sent without an electrical signal flowing to the part that is exposed to hydrogen. In addition, because it is designed to transmit and receive probe beams using an optical fiber, remote hydrogen detection is possible through the separation of the sensor and the signal processing unit