Mathematical modeling and simulation of microfluidic flow in gas sensors

Date

2023-7-05

Author

Yurttutan, Hale

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Semiconductor metal oxide gas sensors are found extensive use in both industrial settings and household settings that enable the detection and quantification of various gases serving different purposes such as safety and process control. Carbon monoxide (CO) detection is vital because of its potential toxic effects on human health. This study provides a comprehensive investigation into the sensing behavior of a SnO2-based porous metal oxide gas sensor in response to CO by utilizing COMSOL Multiphysics. In this study, CO gas in an excess oxygen environment is introduced with an inlet velocity to a measurement chamber, and the time-dependent response of the sensor is investigated. The model encompasses convective and diffusive mass transfer, reaction kinetics, conductance, and electrical current models. The dynamic ionized oxygen density is established as a connection between the gas concentration and the conductance of the sensor. The sensor’s response is investigated for varying carbon monoxide concentrations, inlet velocities, temperatures, thicknesses, and porosities. The findings indicate that the competing effect of reaction and diffusion mainly determines the overall distribution inside the sensing film. Additionally, the longitudinal distribution of CO concentration highlighting the impact of CO molecules carried along the air flow was supported by the investigation of the local Sherwood number. The effect of CO inlet concentration on the sensor's conductance and sensitivity demonstrated that an increase in CO inlet concentration leads to higher conductance and a progressive increase in sensitivity. However, the sensitivity eventually reaches a plateau due to the saturation of reactive sites. In addition, the effect of inlet velocity, and horizontal/vertical flow configurations on the conductance profile were investigated. The effect of temperature on conductance and sensitivity was examined based on the competing effect of consumption and recovery of the ionized oxygen density. Furthermore, the study reveals an inverse relationship between sensitivity and the thickness of the sensing film while demonstrating a direct proportionality between sensitivity and porosity.

Subject Keywords

Semiconductor Metal Oxide, Microfluidic Flow, CO Detection, Gas Sensor Modeling, Computational Modeling

URI

https://hdl.handle.net/11511/104520

Collections

Graduate School of Natural and Applied Sciences, Thesis