Development of Microfluidic Mixer at LiX Beamline for Studying Biomolecular Structural Kinetics

Abstract

A microfluidic mixer with capability of measuring in a time domain starting from few 10's of microseconds to couple of seconds is currently being designed and fabricated. It will be installed at High Brilliance X-ray Scattering for Life Sciences (LiX) beamline. This mixer relies on introducing chaotic segments in the fluid pathway to increase the mixing efficiency without significantly increasing the sample volume. The verification of the conceptual mixer design and subsequent optimization of mixing performance was carried out through extensive FEA simulation using COMSOL Multiphysics software. The design emphasizes on accessing smallest measurable time and low sample consumption. Based on our simulations the split-and-recombination (SAR) mixer is considered best for our needs. Calculations showed that only one such chaotic segment would be enough if a proper mixing flow rate is used, this significantly helps reducing the dead time of the instrument. The uniformity of the flow in the channel is maintained by introducing constrictions along the length of the channel, which considerably improves the flow profile in comparison with a design with two smooth walls. The mixer consists of three channels, with two outer channel carrying the fluid A and the central channel flushed with fluid B. Theoretical calculations showed that high mixing rate is achieved in the central channel as approximately 80% concentration of outer channel diffuses in the central channel whereas about 90% concentration of central channel is retained.This work is supported by the US National Institutes of Health.