Gas Sensor Theory from Gas Dynamics to Electric Transport

Liu Hua-Hsing^1*, Yen Ting-Yu¹, Huang Tzu-En¹, Kuang-Yao Lo¹

¹Department of Physics, National Cheng Kung University, Tainan, Taiwan

* Presenter:Liu Hua-Hsing, email:joan99884@gmail.com

When delving into the intricacies of gas sensor mechanisms, one is confronted with numerous factors to consider, as the underlying principles governing gas sensors are highly complex. This complexity extends into the field of gas dynamics, encompassing intricate chemical reactions occurring on the sensor's surface, ultimately leading to changes in the electrical properties of the sensor material. In the context of this study, we have aimed to develop a comprehensive sensor theory based on the foundational Boltzmann transport theorem. Within this theoretical framework, we have seamlessly integrated the well-established Langmuir gas adsorption theorem, along with an additional gas flow correction term. This extension of the sensor theory enhances its scope and relevance.
To empirically confirm the impact of gas flow on sensor response, a meticulously designed experiment was carried out. The observed results of this experimental effort have been systematically correlated with the phenomenon of surface adsorption. As a result, the resulting equation governing conductivity and gas adsorption exhibits a commendable level of simplicity and clarity. Remarkably, the experimental results obtained by applying a gas spray to a SnO2 sample have shown a remarkable alignment with the trends predicted by the theoretically grounded framework

Keywords: gas sensor, Boltzmann transport theorem, surface physics, gas adsorption