Undergraduate Construction of an Optical Tweezer Apparatus with a Study of Brownian Motion on Micron-Sized Polystyrene spheres
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Authors
Bisson, Yannich
Bucciarelli, Dean
de Lint, Maaike
Hasting, Daniel
Jafs, Michael
Reed, Madison
Date
2021-05-26
Type
technical report
Language
en
Keyword
optics , physics
Alternative Title
Abstract
In this experiment, an apparatus is designed for use with optical trapping of
polystyrene spheres with diameters ranging from 1-5 µm. The goal of the experiment
is to first construct a working apparatus that is capable of producing an optical trap,
then to make measurements of the trap stiffness and the maximum force imparted
on the spheres by the trap for each sphere size. It is known that trapped particles
exhibit Brownian motion when suspended in aqueous solution. Due to a constrain
on time, we do not examine the effects mentioned above regarding trapping of particles with laser light and instead choose to focus our attention on analyzing the
behaviour of a 4.5µm sphere in aqueous solution. Theory suggests that the MSD
(Mean Squared Displacement) of polystyrene spheres as a function of time should
follow a linear trend. The data we collected is not consistent with this predicted
trend which we believe is a result of gravitational forces present given our experimental apparatus that went unaccounted for in our analysis.