Influence of Thermal Time Constant of a Micro-Fabricated Thermal Modulator ( $\mu $ TM) for Comprehensive Microscale 2-D Gas Chromatography ( $\mu $ GC $\times \mu $ GC)

Designing a high-performance a micro-fabricated thermal modulator (μTM) is critical for realizing a portable comprehensive microscale 2-D gas chromatography (μGC ×μGC) system. However, there is little fundamental understanding of the physics governing two-stage thermal modulation. Toward that goal, we perform finite element and analytical modeling based on convection-diffusion equations and obtain excellent match with experimental results. We demonstrate that unlike bench-top TMs, species are not immobile during the trapping phase of modulation. A 10% decrease in time-constant of the first stage improves peak capacity of μGC ×μGC, full-width-at-half-height of the modulated peak proportionately, and reduces breakthrough by ~70%. Due to the high cost of micro-fabrication, it is prohibitively expensive to perform such studies experimentally. Performing design optimizations numerically using such models could lead to the realization of portable μGC ×μGC systems and low-cost bench-top μTMs. We conclude by suggesting some possible improvements to our μTM design.