Collection, focusing, and metering of DNA in microchannels using addressable electrode arrays for portable low-power bioanalysis

Although advances in microfluidic technology have enabled increasingly sophisticated biosensing and bioassay operations to be performed at the microscale, many of these applications employ such small amounts of charged biomolecules (DNA, proteins, peptides) that they must first be pre-concentrated to a detectable level. Efficient strategies for precisely handling minute quantities of biomolecules in microchannel geometries are critically needed, however it has proven challenging to achieve simultaneous concentration, focusing, and metering capabilities with currentgeneration sample injection technology. Using microfluidic chips incorporating arrays of individually addressable microfabricated electrodes, we demonstrate that DNA can be sequentially concentrated, focused into a narrow zone, metered, and injected into an analysis channel. The technique used in this research transports charged biomolecules between active electrodes upon application of a small potential difference (1 V), and is capable of achieving orders of magnitude concentration increases within a small device footprint. The collected samples are highly focused, with sample zone size and shape defined solely by electrode geometry. In addition to achieving the objectives of the research project, this setup was found to provide added functionality as a label-free biomolecule detection technique due to the formation of light scattering phases of charged biomolecules on top of the capture electrode.