In-line DNA preconcentration, size separation, and single molecule detection without applied electric fields

We describe an in-line microfluidic preconcentration method that does not require electrodes or an externally applied electric field. We demonstrate that this method, that we call Counter Flow Concentration (CFC), is stable for long time spans and can achieve concentration factors exceeding 3 orders of magnitude. We also couple CFC with Single Molecule Free Solution Hydrodynamic Separation (SML-FSHS) to perform highly sensitive DNA analysis through the integration of in-line, electric field free DNA preconcentration, size-based separation, and single molecule detection.