MEMS-based multi-inlet/outlet preconcentrator coated by inkjet printing of polymer adsorbents

Preconcentration plays a major role in the quantitative analysis of gas mixtures. Using microfabrication technology, a microthermal preconcentrator (μTPC) device with high-aspect-ratio 3D structures (240 μm) is presented. The silicon-glass die has outer dimensions of 7 mm × 7 mm, total inner surface area of ∼200 mm2, and a total inner volume of ∼6.5 μL. The μTPC has on-chip thermal desorption capability and comprises more than 3500 micropillars with dimensions of 27 μm × 115 μm × 240 μm. To enhance preconcentration capability, the device was coated with a uniform polymer adsorbent film using a high coverage coating method based on the principle of inkjet printing technology and heated with off-board high-performance ceramic heater. The effect of the distributed inlet/outlet on the μTPC performance has been explored using computational fluid dynamics (CFD) analysis and verified by experimental results. The μTPC demonstrated a very sharp reproducible desorption peak which is needed for fast analytical analysis. A concentration factor of 1000 using Tenax TA adsorbent was achieved. The μTPC was used as a gas chromatography (GC) injector to demonstrate its capability in concentrating a dilute multi-compound hydrocarbon mixture into a sharp pulse suitable for gas chromatographic analysis. The performance of the μTPC was evaluated in terms of adsorption capacity, pillar packing density, and inlet pressure. It was found to be in agreement with the breakthrough model.