Tweezers

An optical tweezer is a scientific instrument that uses a focused laser beam to provide an attractive force (typically on the order of piconewtons) to physically hold and move microscopic dielectric objects. more...

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Optical tweezers have been particularly successful in studying a variety of biological systems in recent years.

History and development

The detection of optical scattering and gradient forces on micrometer sized particles was first reported in 1970 by Arthur Ashkin, a scientist working at Bell Labs. Years later, Ashkin and colleagues reported the first observation of what is now commonly referred to as an optical trap: a tightly focused beam of light capable of holding microscopic particles stable in three dimensions.

One of the authors of this seminal 1986 paper, Steven Chu, would go on to use optical tweezing in his work on cooling and trapping atoms. This research earned Chu the 1997 Nobel Prize in Physics.. In an interview, Steven Chu described how Askhin had first envisioned optical tweezing as a method for trapping atoms. Ashkin was able to trap larger particles (10 to 10,000 nanometers in diameter) but it fell to Chu to extend these techniques to the trapping of atoms (0.1 nanometers in diameter).

In the late 1980s, Arthur Ashkin and his colleagues first applied the technology to the biological sciences, using it to trap an individual tobacco mosaic virus and Escherichia coli bacterium. Throughout the 1990s and afterwards, researchers like Carlos Bustamante, James Spudich, and Steven Block pioneered the use of optical trap force spectroscopy to characterize molecular-scale biological motors. These molecular motors are ubiquitous in biology, and are responsible for locomotion and mechanical action within the cell. Optical traps allowed these biophysicists to observe the forces and dynamics of nanoscale motors at the single-molecule level; optical trap force-spectroscopy has since led to greater understanding of the stochastic nature of these force-generating molecules.

Optical tweezers have proven useful in other areas of biology as well. For intance, in 2003 the techniques of optical tweezers were applied in the field of cell sorting; By creating a large optical intensity over the sample area filled with micro-biological sample, the cell can be sorted by its intrinsic optical characteristics. . Optical tweezers have also been used to probe the cytoskeleton, measure the visco-elastic properties of biopolymers, and study cell motility.

The Physics of Optical Tweezers

Read more at Wikipedia.org