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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.

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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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    Item Type: University of Pittsburgh ETD
    Creators/Authors:
    CreatorsEmailORCID
    Li, Dongxiaodongxli@gmail.com
    ETD Committee:
    ETD Committee TypeCommittee MemberEmailORCID
    Committee ChairKim, Hong Koohkk@pitt.edu
    Committee MemberLi, Guangyonggul6@pitt.edu
    Committee MemberFalk, Joelfalk@pitt.edu
    Committee MemberLeuba, Sanford Hleuba@pitt.edu
    Committee MemberStanchina, Williamwes25@pitt.edu
    Title: Interactions of Electromagnetic Waves With Micro/Nano Particles: Manipulation and Characterization
    Status: Unpublished
    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.
    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; The work is available for access worldwide immediately.
    Patent pending: No
    Institution: University of Pittsburgh
    Thesis Type: Doctoral Dissertation
    Refereed: Yes
    Degree: PhD - Doctor of Philosophy
    URN: etd-03302011-115214
    Uncontrolled Keywords: Gold nanoparticles; Heat generation; Nanoslits; Optical trapping; Radiofrequency
    Schools and Programs: Swanson School of Engineering > Electrical Engineering
    Date Deposited: 10 Nov 2011 14:33
    Last Modified: 04 Apr 2012 11:58
    Other ID: http://etd.library.pitt.edu/ETD/available/etd-03302011-115214/, etd-03302011-115214

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