Micro-Heater Integrated Nanotube Array Gas Sensor for Parts-Per-Trillion Level Gas Detection and Single Sensor-Based Gas Discrimination

Ensuring chemical safety and safeguarding human health require real-time monitoring and discrimination of trace gases using appropriate gas sensors. Typically, this task involves expensive, bulky, and power-intensive devices such as optical and electrochemical gas sensors. Achieving this objective with a single, miniature, low-power semiconductor gas sensor is challenging due to selectivity issues.<br/>In this study, we demonstrated a novel gas sensor called micro-heater integrated nanotube array gas sensor (MINA sensor), which can operate in dual modes. The sensor can detect multiple gases at parts-per-trillion (ppt) level under the continuous heating (CH) mode and distinguish multiple gases under the pulse heating (PH) mode. We constructed the MINA sensor on the nano-porous anodic aluminum oxide (AAO) templates with a top-bottom electrode structure, which significantly increases the sensor's surface area for molecular access. To create the sensing material layer, we used atomic layer deposition to deposit an ultrathin and conformal SnO₂ thin film and decorated it with Pd nanoparticles. When operating under the CH mode, the MINA sensor could detect hydrogen, acetone, toluene and formaldehyde with measured LODs as low as 100 ppt, 100 ppt, 100 ppt, 4 ppb, with the corresponding theoretical LODs as 6.96 ppt, 11.88 ppt, 16.52 ppt, 70.06 ppt, respectively. Under PH mode, the MINA sensor provided varying transient responses to different gases due to the variations of gas diffusion and surface reaction activation energy of the gases. By analyzing the conductance amplitude and slope features of a single pulse, different concentrations of hydrogen, acetone, toluene, and formaldehyde can be distinguished. Furthermore, the PH mode saved 66.7% energy compared to the traditional CH mode. The remarkable capabilities of the MINA sensor make it highly appealing for various applications, including distributed low-power sensor networks and battery-powered mobile sensing systems for chemical safety, environmental monitoring, and healthcare.