An optical trapped gripper for manipulating micron-sized particles

Optical tweezers use the electric-field gradient-force associated with tightly focused laser beams to trap micron-sized objects at the beam focus. Over the last few years optical tweezers have been revolutionized by the addition of spatial light modulators to split the laser beam into many traps that can be individually controlled; a technique called holographic optical tweezers. However, the reliance of optical tweezers on the gradient-force largely restricts their application to transparent objects that are not unduly sensitive to the effects of the laser light. Consequently, the manipulation of metallic particles or sensitive biomaterials can be problematic. In this work we use a holographic tweezers to position multiple silica beads acting as an optical gripper to lift, rotate and move micron-sized objects that otherwise do not lend themselves to tweezers control. We illustrate the use of the optical gripper under real-time joystick control to manipulate micron-sized metallic particles with nano-scale precision.