Recovery of rare cells using a microchannel apparatus with patterned posts

A microflow apparatus comprising:

• a body having a randomized flow path which comprises an inlet, an outlet, and a microchannel arrangement extending between said inlet and outlet to form a collection region, the flow path designed to support a fluid flow rate of 0.01 to 100 mm/second,
• wherein:
• said microchannel arrangement includes a plurality of transverse separator posts being integral with a base surface of said microchannel and projecting therefrom and arranged in a random and irregular pattern, wherein said random and irregular pattern is designed according to the following parameters 1) the posts having at least three different cross-sectional sizes in the range of about 70 to about 130 microns in diameter, 2) random arrangement of relative spacing of the posts, and 3) the combination of spacing among the posts and different cross-sectional sizes of posts resulting in the posts occupying about 15% to about 25% of the total volume of the collection region,
• the randomized flow path is configured for cell capture, and
• when in operation said microchannel is connected to a pump to support the continuous flow of liquid sample at a flow rate of 0.01 to 100 mm/second.