Tool fabrication for automated indirect optical micro-manipulation

Abstract

Indirect optical micro-manipulation refers to mechanical manipulation of microscopic objects by means of optically trapped micro-tools. Two-photon polymerization is used to prepare the micro-tools, which are then trapped by focused laser beams through their spherical “handle” parts. Simultaneous control of several laser traps by Holographic Optical Tweezers (HOT) allows for positioning (both transfer and rotation) of the micro-tools in 3D. We report on the development of micro-tools and their testing in an automated HOT system. In order to facilitate the manipulation of objects in large systems (exceeding the field-of-view of the trapping microscope objective) the HOT apparatus is equipped with an additional low-resolution microscope. The two live images are processed with the system of several computers communicating with each other via local network and displayed side-by-side on remote client computer to allow interaction with the user. Initially, the user clicks the positions of laser traps matching micro-tool handles. Subsequently, traps are merged into a set with one representative control point serving for manual mouse operations (drag and drop, rotation and by mouse wheel). In the autopilot mode, the micro-tool moves in the given direction and velocity until it reaches the image border where it turns back. In the simulator mode, the manipulation is performed with animated micro-tools instead of real ones captured by camera.