Method and apparatus for analysis and sorting of polynucleotides based on size

A method for transporting molecules in a microfluidic device, said method comprising:

• a) providing a sample comprising molecules;
• b) providing a microfluidic device comprising an inlet, a first microfluidic channel in fluidic communication with a second microfluidic channel, wherein said first and second microfluidic channels intersect at a junction, and wherein said first microfluidic channel is in fluidic communication with said inlet;
• c) transporting said sample into said inlet port and through said first microfluidic channel to said junction with a hydrostatic pressure differential;
• d) at said junction electrophoretically diverting said molecules from said first microfluidic channel into said second microfluidic channel;
• e) transporting said molecules through said second microfluidic channel;
• and
• f) detecting said molecules.