Hydrodynamic trap for single particles and cells.

Trapping and manipulation of microscale and nanoscale particles is demonstrated using the sole action of hydrodynamic forces. We developed an automated particle trap based on a stagnation point flow generated in a microfluidic device. The hydrodynamic trap enables confinement and manipulation of single particles in low viscosity (1-10 cP) aqueous solution. Using this method, we trapped microscale and nanoscale particles (100 nm-15 mum) for long time scales (minutes to hours). We demonstrate particle confinement to within 1 mum of the trap center, corresponding to a trap stiffness of approximately 10(-5)-10(-4) pNnm.