Patent ID: 7094354

Claim:
A microfluidic device for separating a mixture of a liquid and particles subjecting said mixture to low forces comprising: (a) an entry port for receiving a sample of said mixture of a liquid and particles; (b) a capillary passageway in fluid communication by capillary forces with said entry port, optionally containing a hydrophobic or hydrophilic stop; (c) an elongated separation chamber having proximal and distal ends, said proximal end being in fluid communication by capillary forces with said capillary passageway of (b), and said distal end being closed, said separation chamber comprising (1) a volume for receiving at least a portion of said sample; (2) a depth to particle diameter ratio of about 5/1 to 100/1, said ratio being chosen to avoid clogging of the chamber with said particles and as a function of the force to be applied to said mixture; and (3) a wall surface having a surface energy equal to or less than the surface energy of said particles to facilitate separation of said sample by attraction of said particles to said wall surface; (d) a vent for removing air from the entry port of (a) and the separation chamber of (c) displaced by said sample.