On the competition between mixing rate and uniformity in a coaxial hydrodynamic focusing mixer.

On the competition between mixing rate and uniformity in a coaxial hydrodynamic focusing mixer.
Anal Chim Acta. 2020 Mar 22;1103:1-10
Authors: Huyke DA, Ramachandran A, Oyarzun DI, Kroll T, DePonte DP, Santiago JG
Abstract
Fast microfluidic mixers for use with line-of-sight integrating detection schemes pose unique challenges. Such detectors typically cannot discriminate signal from slow moving (e.g. near internal walls) and fast-moving portions of the fluid stream. This convolves reaction rate dynamics with fluid flow residence time dynamics. Further, the small cross sections of typical three-dimensional hydrodynamic focusing devices lead to lower detection signals. The current study focuses on achieving both small time scales of mixing and homogenous residence times. This is achieved by injecting sample through a center capillary and hydrodynamically focusing using a sheath flow within a tapered second capillary. The current design also features a third, larger coaxial capillary. The mixed stream flows into the large cross-section of this third capillary to decelerate and expand the stream by up to 14-fold to improve line-of-sight signal strength of reaction products. Hydrodynamic focusing, mixing, and expansion are studied using analytical and numerical models and also studied experimentally using a fluorescein-iodide quenching reaction. The experimentally validated models are used to explore trade-offs between mixing rate and uni...

Source: Analytica Chimica Acta - February 23, 2020 Category: Chemistry Authors: Huyke DA, Ramachandran A, Oyarzun DI, Kroll T, DePonte DP, Santiago JG Tags: Anal Chim Acta Source Type: research