title: Characterizing diffusion and transport in microfluidics channels: a combined Raman microscopy and band-target entropy minimization study.
abstract: With the increasing use of microfluidics, there is a need for a rather general experimental approach in order to monitor and characterize transport effects. Indeed, micro-fabrication methods have allowed the inclusion of numerous new structures and devices within microfluidics channels,  and such alterations in flow patterns should impact solute transport characteristics. In the present contribution, Raman microscopy is combined with band-target entropy minimization analysis (BTEM) in order to rapidly assess and map concentration profiles in various regions of a microfluidics  device. Two isotopomers, CHCl(3) and CDCl(3), are contacted under laminar conditions. Special consideration is given to the point of contact between the two liquids, transport in straight sections, transport in curved sections, and wall effects. Break-through curves confirmed  that stagnation of fluid at the wall is not occurring, despite substantial wall roughness. Since the methods used in the present study are quite general, they should be useful in rapidly accessing transport effects when fluids (also in conjunction with colloids, suspensions, and solids) are  contacted in the presence of both simple as well as complex geometries.
authors.affiliation: Process Science and Modeling, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), 1 Pesek Rd., Jurong Island, Singapore 627833. effendi_widjaja@ices.a-star.edu.sg
authors.forename: Effendi
authors.initials: E
authors.lastname: Widjaja
authors.forename: Siew Yen
authors.initials: SY
authors.lastname: Teh
authors.forename: Marc
authors.initials: M
authors.lastname: Garland