Direct integration of carbon nanotubes on a suspended Pt microheater for hydrogen gas sensing

The gas-sensing equipment experienced a greater demand in different workplace environments owing to its high capability to detect the unburnt poisonous gases in the boilers or analyzing the airborne pollution levels. The recent trend toward achieving an efficient gas sensor depends on the low-power consumption and miniaturization. In addition, emerging nanomaterials have shown great potential toward gas sensing along with their outstanding electrochemical properties. This work aims toward the sensing of hydrogen gas utilizing carbon nanotubes (CNTs) directly integrated onto a Pt microheater. The pristine CNTs detect hydrogen gas through the change in the electrical resistance. The chemical reaction between the hydrogen molecule and CNTs is promoted at high temperatures by utilizing the microheater. The suggested spray-coated CNT layer survives subsequent microfabrication processes, demonstrating a robust integration method of nanomaterials into conventional microelectromechanical systems (MEMS). CNTs integrated Pt microheater is batch fabricated using a microfabrication technique, allowing a high device yield of over 90%. The fabricated gas sensors demonstrate a low power budget of a few mW and owe a fast response time. The temperature is elevated up to 420 °C by supplying 2.19 mW power for gas sensing, and the change in the rate of resistance change reached 1.82% by supplying hydrogen gas of 10% concentration. The response and recovery time from the microheater are found to be 39 and 35 seconds, respectively. Besides, the decrease in drift factor occurs when the sensor operates at too high temperatures. The gas concentration is controlled and simultaneously the rate of resistance change is evaluated which further helps to obtain a LOD value of 1200 ppm. The Raman spectra of CNTs before and after the gas-sensing experiment confirm that there is no change or degradation of the CNTs during the experimental process. The fabricated CNTs integrated Pt microheater-based gas sensor has immense potential toward sensing hydrogen gas.