Assembly and force measurement with SPM-like probes in holographic optical tweezers

In this paper we demonstrate the optical assembly and control of scanning probe microscopy (SPM)-like probes, using holographic optical tweezers. The probes are formed from cadmium sulphide rods and silica microspheres, the latter providing explicit trapping handles. Calibration of the trap stiffness allows us to use a precise measure of probe displacement to calculate the applied forces. We demonstrate that the optically controlled probe can exert a force in excess of 60 pN, over an area of 1 x 10(-13) m(2), with a force sensitivity of 50 fN. We believe that probes similar to the ones presented here will have applications as nanotools in probing laser-sensitive cells/materials.