Three-dimensional (3D) micro/nano-manipulation using optical tweezers is a significant technique for various scientific fields ranging from biology to nanotechnology. For the dynamic handling of multiple/individual micro-objects in a true 3D working space, we present an improved hybrid optical tweezers system consisting of two multibeam techniques. These two techniques include the generalized phase contrast method with a spatial light modulator and the time-shared scanning method with a two-axis steering mirror and an electrically focus-tunable lens. Unlike our previously reported system that could only handle micro-objects in a two and half dimensional working space, the present system has high versatility for controlled manipulation of multiple micro-objects in a true 3D working space. The controlled rotation of five beads forming a pentagon, that of four beads forming a tetrahedron about arbitrary axes, and the fully automated assembly and subsequent 3D translation of micro-bead arrays are successfully demonstrated as part of the 3D manipulation experiment.
In our previous paper, on dynamic handling of massive micro-bead arrays, we developed a hybrid optical tweezers
system consisting of two multi-beam techniques: the GPC method and the galvano mirrors (GMs) scanning method. This
system had high versatility for manipulating massive arrays, but arrays formed by its GM scanning tweezers could be
handled only in a two-and-half dimensional (2.5D) working space. This limitation arose from the low bandwidth of the
Z-axis manipulation due to the lens translation using a linear stage. For true 3D controlled manipulation of multiple
micro-beads, in this paper, we redesign the GM scanning part of the previous hybrid system using an electrically focus-tunable
lens with high bandwidth. The optical structure is linked to a commercially available microscope via its epifluorescence
port. One set of optical tweezers based on the GPC uses the p-polarized beam, and the other set based on
the GM scanning uses the s-polarized beam. In the results of the 3D manipulation experiment, the controlled rotation of
five beads forming a pentagon and that of four beads forming a tetrahedron about arbitrary axes are demonstrated.
Laser manipulation is an important technique suitable for controlling objects in liquid at length scales ranging from
sub-micrometers to micrometers. However, the use of this technique by itself is not enough to dexterously or automatically
manipulate objects. In this article we propose a concept for automated non-contact micro-manipulation combined with
laser manipulation and advanced control system techniques, and describe the configuration of a developed system, i.e. a
three-beam laser trapping system with excellent user-interfaces, real-time image processing functions and a micro-laser
ablation beam. We also show the results of several demonstrations; namely the arrangement of metallic particles, the
manipulation of a non-spherical object, the laser perforation of a cell, and the automated selection and transportation of
colored micro beads.
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