Research Articles

Accurate measurement of microscopic forces and torques using optical tweezers

Melanie McLaren, Elias Sidderas-Haddad, Andrew Forbes
South African Journal of Science | Vol 107, No 9/10 | a579 | DOI: | © 2011 Melanie McLaren, Elias Sidderas-Haddad, Andrew Forbes | This work is licensed under CC Attribution 4.0
Submitted: 03 January 2011 | Published: 19 September 2011

About the author(s)

Melanie McLaren, National Laser Centre, CSIR, South Africa
Elias Sidderas-Haddad, School of Physics, University of the Witwatersrand, South Africa
Andrew Forbes, National Laser Centre, CSIR, South Africa


It is now well known that matter may be trapped by optical fields with high intensity gradients. Once trapped, it is then possible to manipulate microscopic particles using such optical fields, in so-called optical tweezers. Such optical trapping and tweezing systems have found widespread application across diverse fields in science, from applied biology to fundamental physics. In this article we outline the design and construction of an optical trapping and tweezing system, and show how the resulting interaction of the laser light with microscopic particles may be understood in terms of the transfer of linear and angular momentum of light. We demonstrate experimentally the use of our optical tweezing configuration for the measurement of microscopic forces and torques. In particular, we make use of digital holography to create so-called vortex laser beams, capable of transferring orbital angular momentum to particles. The use of such novel laser beams in an optical trapping and tweezing set-up allows for the control of biological species at the single-cell level.


optical tweezing; angular momentum of light; vortex beams; optical forces; optical trapping


Total abstract views: 1679
Total article views: 2914


Kuyper CL, Chui DT. Optical trapping: A versatile technique for biomanipulation. Appl Spectrosc. 2002;56:300A–312A. doi:10.1366/00037020260377652

Arai Y, Yasuda R, Akashi K, et al. Tying a molecular knot with optical tweezers. Nature. 1999;399:446–448. doi:10.1038/20894, PMid:10365955

Ehrlicher A, Betz T, Stuhrmann B, et al. Guiding neuronal growth with light. Proc Natl Acad Sci USA. 2002;99:16024–16028. doi:10.1073/pnas.252631899, PMid:12456879, PMid:138558

Carnegie DJ, Stevenson DJ, Mazilu M, et al. Guided neuronal growth using optical line traps. Opt Express. 2008;16:10507–10517. doi:10.1364/OE.16.010507, PMid:18607464

Squires TM, Quake SR. Microfluidics: Fluid physics at the nanoliter scale. Rev Mod Phys. 2005;77:977–1026. doi:10.1103/RevModPhys.77.977

Eriksson E, Enger J, Nordlander B, et al. A microfluidic system in combination with optical tweezers for analyzing rapid and reversible cytological alterations in single cells upon environmental changes. Lab Chip. 2007;7:71–76. doi:10.1039/B613650H

Hopkins RJ, Mitchem L, Ward AD, Reid JP. Control and characterisation of a single aerosol droplet in a single-beam gradient force optical trap. Phys Chem Chem Phys. 2004;6:4924–4927. doi:10.1039/b414459g

Ashkin A, Dziedzic JM, Bjorkholm JE, Chu S. Observation of a single-beam gradient force optical trap for dielectric particles. Opt Lett. 1986;11:288–290. doi:10.1364/OL.11.000288, PMid:19730608

Ashkin A. Acceleration and trapping of particles by radiation pressure. Phys Rev Lett. 1970;24:156–159. doi:10.1103/PhysRevLett.24.156

Rohrbach A, Stelzer EHK. Trapping forces, force constants, and potential depths for dielectric spheres in the presence of spherical aberrations. Appl Opt. 2002;41:2494–2507. doi:10.1364/AO.41.002494, PMid:12009161

Smith S, Bhalotra S, Brody A, Brown B, Boyda E, Prentiss M. Inexpensive optical tweezers for undergraduate laboratories. Am J Phys. 1998;67:26–35. 2002;41:2494–2507. doi:10.1119/1.19187

Ashkin A. Forces of a single-beam gradient laser trap on a dielectric sphere in the ray optics regime. Biophys J. 1992;61(2):569–582.

Beth RA. Mechanical detection and measurement of the angular momentum of light. Phys Rev. 1936;50:115–125. doi:10.1103/PhysRev.50.115

Poynting JH. The wave motion of a revolving shaft, and a suggestion as to the angular momentum in a beam of circularly polarised light. Proc R Soc Lond A. 1909;82:560–567. doi:10.1098/rspa.1909.0060

Friese MEJ, Nieminen TA, Heckenberg NR, Rubinsztein-Dunlop H. Optical alignment and spinning of laser-trapped microscopic particles. Nature. 1998;394:348–351. doi:10.1038/28566

Simpson NB, Dholakia K, Allen L, Padgett MJ. Mechanical equivalence of spin and orbital angular momentum of light: An optical spanner. Opt Lett. 1997;22:52–54. doi:10.1364/OL.22.000052, PMid:18183100

Allen L, Beijersbergen MW, Spreeuw RJC, Woerdman JP. Orbital angular momentum of light and the transformation of Laguerre–Gaussian laser modes. Phys Rev A. 1992;45:8185–8189. doi:10.1103/PhysRevA.45.8185, PMid:9906912

He H, Friese MEJ, Heckenberg NR, Rubinsztein-Dunlop H. Direct observation of transfer of angular momentum to absorptive particles from a laser beam with a phase singularity. Phys Rev Lett. 1995;75:826–829. doi:10.1103/PhysRevLett.75.826, PMid:10060128

Fischer P, Little H, Smith RL, et al. Wavelength dependent propagation and reconstruction of white light bessel beams. J Opt A: Pure Appl Opt. 2006;8:477–482. doi:10.1088/1464-4258/8/5/018

Neuman K, Block S. Optical trapping. Rev Sci Instrum. 2004;75:2787–2809. doi:10.1063/1.1785844, PMid:16878180, PMid:1523313

Dholakia K, Reece P, Gu M. Optical micromanipulation. Chem Soc Rev. 2007;37:42–55. doi:10.1039/b512471a, PMid:18197332

Bechhoefer J, Wilson S. Faster, cheaper, safer optical tweezers for the undergraduate laboratory. Am J Phys. 2001;70:393–400. doi:10.1119/1.1445403

Leach J, Mushfique H, Di Leonardo R, Padgett M, Cooper J. An optically driven pump for microfluidics. Lab Chip. 2006;6:735–739.

Neale SL, MacDonald MP, Dholakia K, Krauss TF. All-optical control of microfluidic components using form birefringence. Nat Mater. 2005;4:530–533. doi:10.1038/nmat1411, PMid:15965480

Reader Comments

Before posting a comment, read our privacy policy.

Post a comment (login required)


Crossref Citations

1. Influence of slow light effect on trapping force in optical tweezers
Haotian Chen, Huichuan Lin, P. H. Jones, Ziyang Chen, Songjie Luo, Jixiong Pu
Optics Letters  vol: 47  issue: 3  first page: 710  year: 2022  
doi: 10.1364/OL.448727