Abstract
Optically trapped dielectric particles experience a linear restoring force due to the trapping laser beam for small displacements of the trapped beads from the center of the optical trap. The optical force adds an apparent contribution to the measured shear elastic modulus of the solution in microrheology experiments. Traditional methods of correcting for the effect of the trap and obtaining the true shear elastic modulus of the solution involved taking measurements in separate purely viscous solutions using similar but not identical trapped beads under the same experimental conditions. A new method is proposed in this research to do this correction. It is based on finding the apparent response of the system including solution and trap at two different laser powers then extracting the true medium response from the measured responses. It was found to be an effective method to correct for the optical trap effect for samples of purely viscous solutions that theoretically should have zero elastic shear modulus. It was also tested in a solution of worm-like micelles to check its viability in solutions that have an inherent elastic component of shear modulus. Measurements in water yielded a zero elastic shear modulus and those in micelle solution agreed with previously published data for worm-like micelles solutions. The new method requires less labor and avoids possible sources of error involved in the traditional methods.
Department
Physics Department
Degree Name
MS in Physics
Graduation Date
6-1-2014
Submission Date
May 2014
First Advisor
Addas, Karim
Committee Member 1
Elmeseiry, Medhat
Committee Member 2
Swillam, Mohamed
Extent
59 p.
Document Type
Master's Thesis
Library of Congress Subject Heading 1
Optics.
Library of Congress Subject Heading 2
Optoelectronics.
Rights
The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy.
Institutional Review Board (IRB) Approval
Not necessary for this item
Recommended Citation
APA Citation
ElSabry, E.
(2014).A method of correction for the effect of optical traps in
equilibrium microrheology experiments [Master's Thesis, the American University in Cairo]. AUC Knowledge Fountain.
https://fount.aucegypt.edu/etds/1291
MLA Citation
ElSabry, ElHassan. A method of correction for the effect of optical traps in
equilibrium microrheology experiments. 2014. American University in Cairo, Master's Thesis. AUC Knowledge Fountain.
https://fount.aucegypt.edu/etds/1291
Comments
All experiments for this research were conducted at the Third Institute of Physics-Biophysics (DPI) at the Georg-August University in Göttingen, Germany. The institute also covered all the costs for the materials and equipment used in the project. Funds for the travel and accommodation to work on this project were available through the Graduate Student Grant (Office of the Dean of Graduate Studies at AUC) and the generous support of the institute in Germany.