Abstract
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.
Highlights
The use of laser trapping devices, commonly known as optical tweezers, was first demonstrated by Ashkin in 1970.1 In the past two decades, the laser trapping technique has been further extended to realize multibeam optical tweezers and has been widely used for noncontact micro/nano-manipulation in various scientific fields, in biomedical fields, for applications such as in Lab-on-a-Chip, bio-MEMS/ NEMS, and microfluidic systems
The multibeam techniques used in optical tweezers such as holography,[2] time-shared scanning,[3] and generalized phase contrast (GPC),[4] allow us to trap and manipulate many micro-objects simultaneously, in contrast to mechanical microhands[5] which manipulate only one object at a time
As reported in our previous paper,[6] we have developed a hybrid optical tweezers system, for dynamic handling of massive microbead arrays, consisting of two multibeam techniques including the GPC method using a spatial light modulator (SLM) and the time-shared scanning method using the galvano mirrors (GMs)
Summary
The use of laser trapping devices, commonly known as optical tweezers, was first demonstrated by Ashkin in 1970.1 In the past two decades, the laser trapping technique has been further extended to realize multibeam optical tweezers and has been widely used for noncontact micro/nano-manipulation in various scientific fields, in biomedical fields, for applications such as in Lab-on-a-Chip, bio-MEMS/ NEMS, and microfluidic systems. As reported in our previous paper,[6] we have developed a hybrid optical tweezers system, for dynamic handling of massive microbead arrays, consisting of two multibeam techniques including the GPC method using a spatial light modulator (SLM) and the time-shared scanning method using the galvano mirrors (GMs). The manipulation in a 2.5D working space means that the controlled movement of objects in threedimensional (3D) Cartesian coordinates is limited to 3D translations and two-dimensional (2D) rotations in xy-planes This limitation arose from the lower bandwidth (several hertz in the previous system) of the z-axis manipulation because the manipulation was based on lens translation with a PC-. We present an improved hybrid optical tweezers system that can be used for the controlled 3D manipulation of multiple micro-objects with the help of an electrically focus-tunable lens with higher bandwidth
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