Optical tweezers have been used to trap and manipulate tiny particles including biological cells, viruses and microorganism in the biology field. By modifying the shape of the trapping object the rotation of the objects using radiation pressure was reported. Usually, these micro-objects are fabricated through complicated ion beam etching process. In this work, windmill-shaped micro-rotators are fabricated by simple photolithographic method and rotation properties are examined. The negative photoresist which is spin coated on the glass is placed in contact with photomask and illuminated with ultraviolet light from Hg lamp. The micro-rotator has four arms of 10 micrometers length and side surface area of each arm are different to surrounding medium. Because of the asymmetrical structure, rotational torque is generated when incident laser beam passes through the side walls of the micro-rotator. The rotation speed of the micro-rotator depends on the intensity of incident laser beam, thickness of rotator and focused position of laser beam. When the laser beam is focused slightly above the upper surface of the rotator, the maximum rotation torque is obtained. The rotation speed increases in proportion to incident laser power. For a micro-rotator of 10 microns thick, maximum rotation speed, 24 rpm is attained with a Ar laser power of 75mW.

Date Published: 9 November 2001
PDF: 8 pages
Proc. SPIE 4440, Lithographic and Micromachining Techniques for Optical Component Fabrication, (9 November 2001); doi: 10.1117/12.448049

Published in SPIE Proceedings Vol. 4440:
Lithographic and Micromachining Techniques for Optical Component Fabrication
Ernst-Bernhard Kley; Hans Peter Herzig, Editor(s)