Self-assembled colloidal arrays as three-dimensional nanofluidic sieves for separation of biomolecules on microchips.

We report on a biomolecular sieving system based on the use of ordered colloidal arrays to define the sieve structure within a microfluidic device. A facile microfluidic colloidal self-assembly strategy has been developed to create ordered, robust, three-dimensional nanofluidic sieves within microfluidic devices, with which fast separation of DNA and proteins of a wide size range was achieved. Compared to conventional colloidal deposition procedures, such as vertical deposition, this approach features much faster assembling speed, the absence of drying-caused cracks that may jeopardize the separation performance, and better flexibility to couple with current microfabrication techniques. The flexibility of pore size enabled by this methodology provides separation of biomolecules with a wide size distribution, ranging from proteins (20-200 kDa) to dsDNA (0.05-50 kbp). Under moderate electric fields, complete separation can be finished in minutes, with separation efficiency comparable to gel/polymer-filled or micro-/nanofabricated microsystems. To our knowledge, this is the first demonstration of size separation of biomolecules within self-assembled ordered colloidal lattices embedded within a microfluidic system.