Development of a microhand using direct laser writing for indirect optical manipulation

In this paper, we propose manipulation ability extension of the optical tweezers by developing microhands, which are to use as end-effectors of the laser beam. First, three different 3D micro-scale handles are designed, then manufactured by the two-photon polymerization method with nano-scale resolution of 100 nm. Second, printed microhands are manipulated by multi-spot laser beam which traps and manipulates numerous objects simultaneously. Third, where direct trapping of the target object is not possible due to target objects' features such as size, shape, material, index of refraction, etc., indirect manipulation of the target microobjects is achieved by using the microhands as an extension of optical tweezers. Finally, three different microhand designs are compared in terms of speed and success rate. Furthermore, suitability of different shapes of microhandles against common usage of spherical shape is discussed.