Development of a multichannel microfluidic system with Schlieren imaging microscopy for online chip-based moving boundary electrophoresis.

The concentration gradient detection method based on the Schlieren optics employed for electrophoresis analyses by extending the technology to a multi-channel system using a prototyped microfluidic chip (thinXXS Micro-technology, Germany). The results prove that coupling a chip-based microfluidic device with Schlieren detection is an appropriate approach to improve the electrophoretic separations. The effects of channel's geometry and dimension were investigated by conducting the experiments in channels with different cross sectional areas. Fast kinetic data acquisition of the charge-coupled device (CCD) camera facilitated recording of a time sequence of optical images, demonstrating the potential of the CCD camera as a powerful tool for studying dynamic processes such as diffusion. Diffusion coefficients of sample proteins were measured under static and dynamic conditions, where the static mode demonstrated more accurate results. Furthermore, the Fourier transformation was employed to improve the Schlieren images for quantitative analysis of the diffusion coefficient measurement.