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Interactions of Electromagnetic Waves With Micro/Nano Particles: Manipulation and Characterization

Li, Dongxiao (2011) Interactions of Electromagnetic Waves With Micro/Nano Particles: Manipulation and Characterization. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

Interaction of electromagnetic waves with small particles has been extensively investigated for detection, characterization and manipulation of objects in the micro/nanoscale. Several advanced techniques based on light-particle interaction have been developed and widely used in biomedical research, e.g., trapping of micron-size particles by light and plasmonic photothermal therapy with gold nanoparticles. In this thesis we have developed two new methods of optical trapping by use of planar metal nano-optic structures. One is based on a metallic nanoslit array structure that is designed to allow refractive transmission of light with proper phase retardation at each slit, shaping an incident light into a sharp focus. The metallic nanoslit array lenses were integrated with a fluidic channel cell, and optical trapping of polystyrene microspheres was demonstrated. Another optical trapping method developed in this thesis utilizes the diffraction phenomenon occurring at a thin-film metal edge. Interference of boundary diffraction and free-space transmission waves is found to generate highly localized distribution of light around the metal edge. The electromagnetic field distribution around the edge was calculated by finite-difference-time-domain method, and the 2D trapping forces were estimated by applying a ray optics model. Trapping of a 2-ìm-diameter polystyrene bead was demonstrated, and the trapping force (escape force) is measured to be about 2.2 pN at incident power of 32 mW. Selective trapping and sorting of microspheres by this metal edge trapping is also demonstrated. Use of metal nanoparticle colloidal solutions in conjunction with radiofrequency (RF) waves has recently drawn attention as a possible means to deposit heat in a local confined space for cancer therapy. We investigated the heating effect of gold nanoparticle (Au-NP) colloids in the presence of RF electromagnetic wave, and explored the possible role of Au-NPs in RF energy absorption. Contrary to the previously-taken assumption in this field, we found that Au nanoparticles do not contribute to RF energy absorption. Au-NPs were physically separated from the colloidal solutions via centrifugation, and RF heating and electrical conductivity measurements were performed. The results show that the dominant mechanism of RF-radiation-to-thermal conversion is due to the Joule heating via ionic conduction in the electrolyte solutions.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Li, Dongxiaodongxli@gmail.comdongxli@gmail.com
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairKim, Hong Koohkk@pitt.eduhkk@pitt.edu
Committee MemberLi, Guangyonggul6@pitt.edugul6@pitt.edu
Committee MemberFalk, Joelfalk@pitt.edufalk@pitt.edu
Committee MemberLeuba, Sanford Hleuba@pitt.eduleuba@pitt.edu
Committee MemberStanchina, Williamwes25@pitt.eduwes25@pitt.edu
Date: 27 June 2011
Date Type: Completion
Defense Date: 25 March 2011
Approval Date: 27 June 2011
Submission Date: 30 March 2011
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Electrical Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Gold nanoparticles; Heat generation; Nanoslits; Optical trapping; Radiofrequency
Other ID: http://etd.library.pitt.edu/ETD/available/etd-03302011-115214/, etd-03302011-115214
Date Deposited: 10 Nov 2011 19:33
Last Modified: 04 Apr 2012 15:58
URI: http://d-scholarship.pitt.edu/id/eprint/6657

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