Nanofluidic molecular filters for efficient protein separation and preconcentration

Regular nanofluidic channels, as thin as 20 nm, have been fabricated and used for protein separation and preconcentration. The nanochannels were fabricated by the substrate-bonding method, and the regularity of the nanochannel has been confirmed by cross-section SEM imaging. A nanofilter array device, with an array of 60-120 nm thin nanofilters, was used for separating small biomolecules (short double-stranded DNA and SDS-coated proteins) based on their size. The sieving of biomolecules (which are comparable to or smaller than the nanofilter gap size) is achieved by steric hindrance of biomolecules within nanochannels. The efficiency of this gel-free separation device is comparable to capillary gel electrophoresis, and can be made better by further optimization. In addition, we have developed a novel biomolecule concentrator using a 40 nm nanofluidic channel as a perm-selective membrane. More than a million times preconcentration of dilute protein or peptide solutions was demonstrated, which was enabled by the stability of the device.