Portable Optical Tweezers Kit
Chapter 2:
Product
Description
Page 2
MTN024417-D02
Chapter 2 Product Description
For many people, moving and controlling objects with a beam of light sounds more like the
“tractor beams” of science fiction than reality. However, optical tweezers are devices that
allow precisely that kind of manipulation. Many areas of research use them to measure
small forces on the order of piconewtons
. More exotic applications include the control of
tiny microgears
. Biologists use optical tweezers to manipulate different types of molecules
and cells
In-vitro
fertilization of ova is a typical application example – sperm can be
inserted into ova without mechanical contact, thus maintaining a sterile environment.
In a lab course, various demonstrations and experiments can be performed with an optical
tweezers setup. This kit can be used to carry out basic experiments such as moving small
spheres or cells through a solution. The kit can also be used for more advanced
experiments such as investigating the Brownian motion of objects, and measuring the
optical forces of the tweezers.
The working principle can be explained using concepts usually known to undergraduate
students, such as geometric optics, basic theory of Brownian motion, and Stokes’ friction.
It is an intriguing experience to be able to control objects with a laser beam – and not only
for students!
This Optical Tweezers Kit can be assembled into a complete and fully operating
experimental setup with which particles on the order of microns can be trapped and moved.
The beam path is schematically depicted in Figure 1. It is possible to perform a variety of
experiments using a number of different particles such as polystyrene beads, glass beads,
or starch grains from ordinary corn flour. A special feature of this setup is that it is portable.
It can be moved from room to room without needing disassembly or major readjustment,
making it ideally suited to demonstrate the principle of optical tweezers to students in
seminars or lecture halls.
Optical tweezers are not only intriguing scientific devices. Their inventor, Arthur Ashkin,
also received the 2018 Nobel Prize "for the optical tweezers and their application to
biological systems." As he wrote: “It is surprising that this simple [...] experiment, intended
only to show simple forward motion due to laser radiation pressure, ended up
demonstrating not only this force but the existence of the transverse force component [...]
and stable three-dimensional particle trapping."
We recommend using the OTKBTK sample kit with the setup. The performance was
optimized for the sample slides and the cover glasses provided with the OTKBTK. For
simplicity, we designed the tweezers system to work without immersion oil.
1
K. SVOBODA, S.M. BLOCK: Optical trapping of metallic Rayleigh particles, Optics Letters 19
(1994) 13, 930-932
2
S.L. NEALE, M.P. MACDONALD, K. DHOLAKIA, T.F. KRAUSS: All-optical control of microfluidic
components using form birefringence, Nature materials 4 (2005), 530-533
3
J.E. MOLLOY, M.J. PADGETT: Lights, action: optical tweezers, Cont. Phys. 43 (2002) 43, 241-
258
4
Proc. Natl. Acad. Sci. USA, Vol. 94, pp. 4853-4860 (1997)
Summary of Contents for EDU-OT3
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