November 3, 2003
Source: David G. Grier
References:
D. G. Grier, "A revolution in optical manipulation,"
Nature 424, 810-816 (2003).
Description:
Optical tweezers use the forces exerted by a
strongly focused beam of light to trap and move objects ranging in size from
tens of nanometres to tens of micrometres. Since their introduction in 1986,
the optical tweezer has become an important tool for research in the fields
of biology, physical chemistry and soft condensed matter physics. Recent
advances promise to take optical tweezers out of the laboratory and into the
mainstream of manufacturing and diagnostics; they may even become consumer
products. The next generation of single-beam optical traps offers
revolutionary new opportunities for fundamental and applied research.
This image is a (false-colored) video micrograph of colloidal silica spheres dispersed in water and organized into a micrometer-scale mixer by torque-exerting optical traps known as optical vortices. The 3 x 3 array of optical vortices shown here was created with a computer-designed hologram and projected with the same microscope objective lens used to create the image. Each optical vortex is a ring of intense laser illumination that captures mesoscopic objects with optical gradient forces. Once trapped, the particles are subjected to torques exerted by the orbital angular momentum carried by the the specially prepared beams of light. The particles in each ring circulate at up to 1000 revolutions per minute (RPM), generating hundred-nanometer-scale flows in the surrounding fluid. Optical vortex arrays therefore act as optical assembled and actuated pumps and mixers in the mesoscopic domain.
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