A micro optofluidic system for toluene detection application

Abstract

A new application of metal deposited poly (methyl methacrylate) (PMMA) microchannel for optical detection of toluene in the UV spectrum region is presented in this study. Laser cutting and hole formation in initial PMMA sheets, micro-milling for groove shaping, aluminium deposition on two caps using DC magnetron sputtering for increasing optical path length, and bonding process using thermally-solvent method are the main steps for the microchannel fabrication. The dimensions and length of microchannel are 370 μm × 370 μm and 5 cm, respectively. The SEM and leakage tests are implemented to investigate the quality of the microchannel. Besides, the characterization results indicate that Al deposition has no adverse influence on the bonding process. Our simulation results indicate that the optical path length enhanced by 2.2% and the loss decreased by 48.9% when Al is deposited on the surfaces of the microchannel. Also, the effect of microchannel length on optical path length and loss is investigated using simulation. The optical detection tests are performed in a single step using UV spectroscopy based on absorption for toluene in concentration range within 20–800 ppm. The tests are repeated several times for each toluene concentration. Our experimental observation indicate that the results obtained from this optofluidic system is repeatable with linear gas detection and fast response and perfect selectivity which make it a good candidate for toluene detection applications.