Design, simulation and application of a new micromixing device for time resolved infrared spectroscopy of chemical reactions in solution

Abstract

We present a novel micromachined fast diffusion based mixing unit for the study of rapid chemical reactions in solution with stopped-flow time resolved Fourier transform infrared spectroscopy (TR-FTIR). The presented approach is based on a chip for achieving lamination of two liquid sheets of 10 microm thickness and approximately 1 mm width on top of each other and operation in the stopped-flow mode. The microstructure is made on infrared transmitting calcium fluoride discs and built up with two epoxy negative photoresist layers and one silver layer in between. Due to the highly laminar flow conditions and the short residence time in the mixer there is hardly any mixing when the two liquid streamlines pass through the mixing unit, which allows one to record a mid-IR transmission spectrum of the analytes prior to reaction. When the flow is stopped, the reactant streams are arrested in the flow-cell and rapidly mixed by diffusion due to the reduced interstream distances and the reaction can be directly followed with hardly any dead time. On the basis of two model reactions-neutralisation of acetic acid with sodium hydroxide as well as saponification of methyl monochloroacetate-the performance of the mixing device was tested revealing proper functioning of the device with a time for complete mixing of less than 100 ms. The experimental results were supported by numerical simulations using computational fluid dynamics (CFD), which allowed a reliable, quantitative analysis of concentration, pressure and flow profiles in the course of the mixing process.

Fabrication of miniaturized fluidic devices using SU-8 based lithography and low temperature wafer bonding

“…Other results obtained from experiments that were carried out with the help of the CE-FTIR-setup are presented elsewhere [2,4,5].…”

“…An appropriate material for this purpose is calcium fluoride (CaF 2 ). It shows high transmittance in the mid-IR-range [4].…”

“…This mixing device is used for the investigation of chemical reactions by time resolved FTIR-spectroscopy combined with in situ mixing of two reactants [4,6,7].…”

Design and additive manufacture for flow chemistry

“…Consequently, FTIR has been implemented into µTAS for a variety of applications. 107 In general, these approaches have been achieved via the capping of microfluidic channels with IR transparent materials, or via off chip FTIR detection.…”

Modeling of cell sorting and rare cell capture with microfabricated biodevices

“…, and while time-and resource-consuming, the results obtained are often very reliable [21]. One of the major challenges is that narrow-bore channels have large aspect ratios, usually more than an order of magnitude (ratio of diameter and length) that makes meshing complex and requires the use of position-dependent discretization.…”