optical tweezers (original) (raw)
Definition: arrangements for capturing and moving particles with laser beams
Alternative terms: laser tweezers, single-beam gradient force traps
methodsRelated: light forceslaser applications
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DOI: 10.61835/jxv Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn
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Contents
What are Optical Tweezers?
Optical tweezers are tools for manipulating small items using light. As early as 1970, it was demonstrated that laser beams can be used to trap and move small particles, e.g. micron-sized latex spheres in water. This is possible due to various kinds of light forces. In the mid-1980s, Arthur Ashkin at AT&T Bell Laboratories greatly pushed and refined this technology, trapping single atoms and later individual viruses and Escherichia coli bacteria with a laser beam, which was tightly focused to a small spot with a microscope objective. It was shown that bacteria can stay alive for long times and even multiply while being trapped by optical tweezers, provided that a suitable (mid-infrared) laser wavelength is chosen (where little light is absorbed).
Optical tweezers can be used with Gaussian beams from lasers, but Bessel–Gauss beams have been shown to have particularly attractive features [8].
Use in Biology
The forces exerted by optical tweezers, e.g. on a bacterium, are small in absolute terms — usually not more than a few piconewtons — but still large enough to prevent a bacterium from escaping and to pull it through water at a relatively high speed.
Optical tweezers can also be used as an optical levitation trap, where a small particle is suspended in air, and gravity is compensated by the light forces. Smaller forces are required for particles in a liquid. This has been shown to work even with a supercontinuum source [4], which at the same time makes it possible to carry out spectroscopic investigations of the captured particle.
As the given examples illustrate, the main application of optical tweezers is in microbiology. They can be used to manipulate single cells, e.g. bacteria, blood cells, or sperm (optically assisted in vitro fertilization), and for experiments on single molecules, e.g. DNA.
Note that there are also various other kinds of optical traps, which are applied to atoms or molecules. These sometimes also involve lasers, apart from electric and magnetic fields.
Nobel Prize in Physics 2018
In October 2018, the Nobel Prize in physics was awarded with one half to Arthur Ashkin for his work on optical tweezers, and the other half jointly to GĂ©rard Mourou and Donna Strickland for their work on chirped-pulse amplification.
Frequently Asked Questions
This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).
What are optical tweezers?
Optical tweezers are tools that use a tightly focused laser beam to manipulate microscopic items such as cells, bacteria, or viruses. This manipulation is possible due to the action of light forces.
What are the main applications of optical tweezers?
The main field of application is microbiology. They are used to manipulate single cells (e.g., bacteria or blood cells) and for experiments on single molecules like DNA. They can also be used for optically assisted in vitro fertilization.
How much force can optical tweezers exert?
The forces are very small, typically in the range of a few piconewtons. While small in absolute terms, this is sufficient to trap a bacterium and move it through water at a relatively high speed.
Who received the Nobel Prize for inventing optical tweezers?
Arthur Ashkin received one half of the 2018 Nobel Prize in Physics for his pioneering work on optical tweezers, which he developed at AT&T Bell Laboratories.
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Bibliography
| [1] | A. Ashkin, “Acceleration and trapping of particles by radiation pressure”, Phys. Rev. Lett. 24 (4), 156 (1970); doi:10.1103/PhysRevLett.24.156 |
|---|---|
| [2] | A. Ashkin and J. Dziedzic, “Optical levitation by radiation pressure”, Appl. Phys. Lett. 18, 283 (1971) |
| [3] | A. Ashkin, “Optical trapping and manipulation of neutral particles using lasers”, Proc. Natl. Acad. Sci. USA 94, 4853 (1997) (review article) |
| [4] | P. Li et al., “Manipulation and spectroscopy of a single particle by use of white-light optical tweezers”, Opt. Lett. 30 (2), 156 (2005); doi:10.1364/OL.30.000156 |
| [5] | C. Liberale et al., “Miniaturized all-fibre probe for three-dimensional optical trapping and manipulation”, Nature Photon. 2, 723 (2008); doi:10.1038/nphoton.2007.230 |
| [6] | A. N. Grigorenko et al., “Nanometric optical tweezers based on nanostructured substrates”, Nature Photon. 2, 365 (2008); doi:10.1038/nphoton.2008.78 |
| [7] | A. Samadi and N. S. Reihani, “Optimal beam diameter for optical tweezers”, Opt. Lett. 35 (10), 1494 (2010); doi:10.1364/OL.35.001494 |
| [8] | T. A. Planchon et al., “Rapid three-dimensional isotropic imaging of living cells using Bessel beam plane illumination”, Nature Methods 8 (5), 417 (2011); doi:10.1038/nmeth.1586 |
| [9] | A. A. R. Neves and C. L. Cesar, “Analytical calculation of optical forces on spherical particles in optical tweezers: tutorial”, J. Opt. Soc. Am. B 36 (6), 1525 (2019); doi:10.1364/JOSAB.36.001525 |
| [10] | J. Gieseler et al., “Optical tweezers — from calibration to applications: a tutorial”, Advances in Optics and Photonics 13 (1), 74 (2021); doi:10.1364/AOP.394888 |
| [11] | H. Hwang et al., “Optical tweezers throw and catch single atoms”, Optica 10 (3), 401 (2023); doi:10.1364/OPTICA.480535 |
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