Laminar flow-based separations of colloidal and cellular particles

A method of separating one or more larger cells from one or more smaller cells in a first fluid flow, comprising:

• receiving the first fluid flow comprising said one or more larger cells and said one or more smaller cells in a microfluidic channel;
• optionally receiving a second fluid flow in the channel adjacent to said first fluid flow, the first fluid flow and the second fluid flow both flowing under laminar conditions in the channel;
• separating said one or more larger cells from said first fluid flow using a plurality of obstacles, said obstacles differentially deflecting said one or more larger cells to a first outlet port by physically contacting said one or more larger cells, wherein each of said plurality of obstacles is staggered in position as compared to an upstream obstacle;
• directing at least a portion of said first fluid flow through a second outlet port;
• and
• directing said one or more larger cells through said first outlet port.