Optical tweezers are scientific instruments that use a highly focused laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 beam to provide an attractive or repulsive force (typically on the order of piconewtons), depending on the refractive index

Refractive index

In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

 mismatch to physically hold and move microscopic dielectric

Dielectric

A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...

 objects. Optical tweezers have been particularly successful in studying a variety of biological systems in recent years.
The detection of optical scattering and gradient forces on micrometer sized particles was first reported in 1970 by Arthur Ashkin

Arthur Ashkin

Arthur Ashkin is a retired scientist who worked at Bell Laboratories and Lucent Technologies. He has started his work on manipulation of microparticles with laser light in the late 60s which has resulted in the invention of optical tweezers in 1986. He has pioneered the optical trapping process...

, a scientist working at Bell Labs

Bell Labs

Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...

.