Microfluidic technologies for matrix-free DNA separation

DNA separation by size by gel electrophoresis is the workhorse of molecular biology. This technology is extremely powerful for fragments in the range 0.1-30 kilo base pairs, but its performances for molecules of higher molecular weights are limited. Furthermore the use of a matrix of polymer gels (or solution at very high concentration) is a strong limitation for its integration in Lab-on-Chip format. We recently developed a technology for DNA separation by size using electro-hydrodynamic transport of DNA in viscoelastic fluids (see upper panel of the Figure). The technology offers key advantages for high molecular weight molecules manipulation, but also for spatial manipulation and sorting.

DNA spatial separation with no separation matrix relies on conventional electric and hydrodynamic actuation. The key idea behind this technology is to force a transport mode, in which migration is size-dependent along one direction and size-independent in the orthogonal one. By forcing a tilted electric field (between the right and left channel in the SEM picture of the Figure), the migration of DNA is controlled by electrophoresis in one direction and by electro-hydrodynamic transport along the other one. The resulting velocity direction is thus dependent on DNA MW, as shown by the fluorescence micrographs of the lower right panel in the figure.

Figure legend: The upper left panel sketches DNA transport in electro-hydrodynamic fluid flows, and the chromatogram in the right represents the separation of a DNA extend ladder in a capillary with this technology (DNA sizes are indicated as insets). The lower panel shows the technology for spatial separation with DNA molecules arriving in a sheet-pattern and conveyed laterally with an electric field oriented from the left to right channels. The intensity of the electric field is given in the insets of the fluorescence micrographs.