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- Title
- GOLD NANOPARTICLE GENERATION USING IN SITU REDUCTION ON A PHOTORESIST POLYMER SUBSTRATE.
- Creator
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Clukay, Christopher, Kuebler, Stephen, University of Central Florida
- Abstract / Description
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This report presents evidence that in-situ reduction of metal ions bound to a cross-linked polymer surface does not always result in nanoparticle formation solely at the interface, as is commonly assumed, but also as much as 40 nm deep within the polymer matrix. Tetrachloroaurate ions were bound using a variety of multi-functional amines to cured films of SU-8 -- a cross-linkable epoxide frequently used for micro- and nanofabrication -- and then treated using one of several reducing agents....
Show moreThis report presents evidence that in-situ reduction of metal ions bound to a cross-linked polymer surface does not always result in nanoparticle formation solely at the interface, as is commonly assumed, but also as much as 40 nm deep within the polymer matrix. Tetrachloroaurate ions were bound using a variety of multi-functional amines to cured films of SU-8 -- a cross-linkable epoxide frequently used for micro- and nanofabrication -- and then treated using one of several reducing agents. The resulting gold-nanoparticle decorated films were examined by X-ray photoelectron spectroscopy and by plan-view and cross-sectional transmission electron microscopy. Reduction using sodium borohydride or sodium citrate generates bands of interspersed particles as much as 40 nm deep within the polymer, suggesting both the Au(III) complex and the reducing agent are capable of penetrating the surface and affecting reduction and formation of nanoparticles within the polymer matrix. It is shown that nanoparticle formation can be confined nearer to the polymer interface by using hydroquinone, a sterically bulkier and less flexible reducing agent, or by reacting the surface in aqueous media with high molecular-weight multifunctional amines, that presumably confine Au(III) nearer to the true interface. These finding have important implications for technologies that apply surface bound nanoparticles, including electroless metallization, catalysis, nano-structure synthesis, and surface enhanced spectroscopy.
Show less - Date Issued
- 2011
- Identifier
- CFH0004091, ucf:44794
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004091
- Title
- BASIC STUDY OF MICROMACHINED DEP (DIELECTROPHORETIC) MANIPULATOR.
- Creator
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Sundaram, Vivek, , K.B.Sundaram, University of Central Florida
- Abstract / Description
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The capability of manipulating microparticle in small volumes is fundamental to many biological and medical applications, including separation and detection of cells. The development of microtools for effective sample handling and separation in such volumes is still a challenge. DEP (dielectrophoresis) is one of the most widely used methods in handling the microparticles. In this thesis we show that forces generated by nonuniform electric field (DEP) can be used for trapping and separating...
Show moreThe capability of manipulating microparticle in small volumes is fundamental to many biological and medical applications, including separation and detection of cells. The development of microtools for effective sample handling and separation in such volumes is still a challenge. DEP (dielectrophoresis) is one of the most widely used methods in handling the microparticles. In this thesis we show that forces generated by nonuniform electric field (DEP) can be used for trapping and separating the microparticles (latex beads). This work further explores the DEP force based on different electrode geometries and medium conductivity. A micromanipulator for latex bead separation was designed, fabricated and characterized. For the development of DEP manipulator, the fabrication and packaging of microfluidic structure with the microelectrode is crucial for reliable analysis. A combination of SU-8 photoresist and polydimethylsiloxane polymer was used for this purpose. Besides, the DEP manipulator, preliminary study on a Coulter counter was conducted. The Coulter counter works on the principle of resistive pulse sensing. This counter is used for counting the beads as they pass through the microfluidic channel. Its possible integration with the manipulator was also explored.
Show less - Date Issued
- 2004
- Identifier
- CFE0000121, ucf:46178
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000121
- Title
- Improved system for fabrication and characterization of nanophotonic devices by multi-photon lithography.
- Creator
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Sharma, Rashi, Kuebler, Stephen, Zou, Shengli, Huo, Qun, Beazley, Melanie, Phanstiel, Otto, University of Central Florida
- Abstract / Description
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A new system for multi-photon lithography (MPL) was developed and used to fabricate three-dimensional (3D) structures with higher aspect ratio, better resolution, improved fidelity, and reduced structural distortion relative to a conventional implementation of MPL.A set of curved waveguides (Rbend = 19 (&)#181;m, and 38 (&)#181;m) and straight waveguides (length = 50 (&)#181;m, Rbend = ?) were fabricated in an epoxide photopolymer and optically characterized using light having a wavelength in...
Show moreA new system for multi-photon lithography (MPL) was developed and used to fabricate three-dimensional (3D) structures with higher aspect ratio, better resolution, improved fidelity, and reduced structural distortion relative to a conventional implementation of MPL.A set of curved waveguides (Rbend = 19 (&)#181;m, and 38 (&)#181;m) and straight waveguides (length = 50 (&)#181;m, Rbend = ?) were fabricated in an epoxide photopolymer and optically characterized using light having a wavelength in vacuum of ?0 = 2.94 (&)#181;m. The optical performance of the waveguides was compared to novel spatially-variant photonic crystals (SVPCs) previously studied in the group. The waveguides were found to guide light with 90% lower efficiency, due to mode leakage. The study provides further evidence that SVPCs operate not through total internal reflection, but rather through self-collimation, as designed.3D uniform-lattice photonic crystals (ULPCs) were fabricated by MPL using a commercial acrylate photopolymer. The ULPCs were optically characterized at ?0 = 1.55 (&)#181;m. A laser beam with adjustable bandwidth was used to measure the self-collimation in the ULPCs. For the low bandwidth beam, vertically polarized light was self-collimated, whereas horizontally polarized light diverged. The transmission efficiency of the ULPCs was also measured as a function of fill factor. The ULPC having a fill factor of 48% exhibited 80% transmission.An etching process was also developed for non-destructively removing Au/Pd coatings that must be deposited onto structures to image them by scanning electron microscopy. The structural and optical integrity of the samples was found to be maintained despite etching. The sputter-coated sample sustained no structural damage when exposed to the ?0 = 1.55 (&)#181;m. However, the metal coating resulted in diminished transmission efficiency due to the high reflection of the 1.55 (&)#181;m beam by the metal coating.
Show less - Date Issued
- 2018
- Identifier
- CFE0007767, ucf:52380
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007767
- Title
- Photophysical and photochemical factors affecting multi-photon direct laser writing using the cross-linkable epoxide SU-8.
- Creator
-
Williams Jr., Henry, Kuebler, Stephen, Elsheimer, Seth, Zhai, Lei, Liao, Yi, Heinrich, Helge, University of Central Florida
- Abstract / Description
-
For the past decade, the epoxy based photoresist SU-8 has been used commercially and in the lab for fabricating micro- and nano-structures. Investigators have studied how processing parameters such as pre- and post-exposure bake temperatures affect the resolution and quality of SU-8 structures patterned using ultraviolet or x-ray lithography. Despite the advances in understanding the phenomena, not all of them have been explored, especially those that are specific to multi-photon direct laser...
Show moreFor the past decade, the epoxy based photoresist SU-8 has been used commercially and in the lab for fabricating micro- and nano-structures. Investigators have studied how processing parameters such as pre- and post-exposure bake temperatures affect the resolution and quality of SU-8 structures patterned using ultraviolet or x-ray lithography. Despite the advances in understanding the phenomena, not all of them have been explored, especially those that are specific to multi-photon direct laser writing (mpDLW). Unlike conventional exposure techniques, mpDLW is an inherently three-dimensional (3D) process that is activated by nonlinear absorption of light.This dissertation reports how several key processing parameters affect mpDLW using SU-8 including pre-exposure bake duration, focal depth, incident laser power, focal-point scan speed, and excitation wavelength. An examination of solvent content of films at various stages in the mpDLW by 1H-NMR shows that even moderate solvent content (over 1 wt-%) affects film viscosity and photoacid diffusion lengths, and can greatly affect the overall fidelity of small features. A study of micro-fabricated feature size versus writing depth in the material shows that even slight refractive index mismatch between SU-8 and the medium between it and the focusing objective introduces spherical aberration that distorts the focus, causing feature size to decrease or even increase in size with writing depth, depending on the average exposure power used. Proper adjustment of the average exposure power was demonstrated as a means to fabricate more uniform features with writing depth. Third, when varying the power and scan speed, it was observed that the feature-size scales with these two parameters in a manner that is consistent with a three-photon absorption mechanism at an excitation wavelength of 800 nm. When aniiiexcitation wavelength of 725 nm is used, the feature-size scaling becomes consistent with that of two photon absorption. This shows that the photoinitiators in the SU-8 can be activated by either two- or three-photon absorption over this wavelength range. Using an irradiance of ~2 TW cm-2 and elongated femtosecond pulses resulted in an observed fourth order power dependence. This observation is in agreement with the literature and suggests that the effective absorptive nonlinearity is also sensitive to pulse duration. These findings will be useful for creating accurate models of the process of mpDLW in SU-8. These models could be used to optimize the processing parameters and develop new processing methods and materials for high-resolution fabrication of robust 3D microstructures. Some of the findings were used to develop a method for fabricating functional microlenses on the tip of optical fibers. This approach opens a new route to functional integrated photonic devices.
Show less - Date Issued
- 2013
- Identifier
- CFE0005441, ucf:50403
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005441
