Understanding microfluidic-based gas detectors: A numerical model to investigate fundamental sensor operation, influencing phenomena and optimum geometries

Abstract

Microfluidic-based gas detectors have been developed as an alternative method to GC/MS systems (which are bulky, expensive, and require trained professionals), and electronics noses (which require extensive calibration due to sensor drift). However, the performance of microfluidic-based gas detectors requires improvements before being commercially-viable in the gas monitoring market. Similar to other approaches, this novel technology requires a multitude of tests to calibrate against different compounds, concentrations, and environmental conditions. This paper presents a 3D numerical simulation to study the response of microfluidic-based gas detectors across various geometries using Multiphysics modeling of diffusion, surface adsorption/desorption, chemical reactions, and heat and momentum transfer phenomena. By using this model, response curves of different analyte concentrations are generated thereby reducing the need for manual calibration tests and associated costs. In this model, diffusion was demonstrated as the main parameter affecting the response, followed by surface adsorption/desorption and heat and momentum transfer, which had a minimal effect on the response. The model was also used to investigate the effect of the detector’s dimensions (including microchannel length, microchannel height, and sensor housing volume) on sensitivity, selectivity and response/recovery time. Due to an observed trade-off between selectivity and sensitivity, a sum indicator was defined to investigate the best overall performance across various conditions. Results obtained from different geometrical dimensions and gas concentrations demonstrated that a change in channel length has the most pronounced impact on the sum indicator, especially for low gas concentrations.