Response to "Comment on 'Influence of random roughness on cantilever curvature sensitivity'" [Appl. Phys. Lett. 96, 226101, (2010)]

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 mu m) for long time scales (minutes to hours). We demonstrate particle confinement to within 1 mu m of the trap center, corresponding to a trap stiffness of similar to 10(-5)-10(-4) pN/nm.