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Characterization of curing kinetics and polymerization shrinkage in ceramic-loaded photocurable resins for large area maskless photopolymerization (LAMP)Kambly, Kiran 17 November 2009 (has links)
Large Area Maskless Photopolymerization (LAMP) is a direct digital manufacturing
technology being developed at Georgia Tech to produce ceramic molds for investment
casting of turbine airfoils. In LAMP, UV light incident on a spatial light modulator is
projected in the form of a structured black and white bitmap image onto a platform
supporting slurry comprising a ceramic particle loaded photocurable resin. Curing of the
resin is completed rapidly with exposures lasting 20~160ms. Three-dimensional parts are
built layer-by-layer by sequentially applying and selectively curing resin layers of 25-100
micron thickness. In LAMP, diacrylate-based ceramic particle-loaded resins with
photoinitiators sensitive in the range of spectral characteristics of the UV source form the
basis for an ultra-fast photopolymerization reaction. At the start of the reaction, the
monomer molecules are separated by van der Waals distance (~10⁴Å). As the reaction
proceeds, these monomer molecules form a closely packed network thereby reducing
their separation to covalent bond lengths (~ 1 Å). This results in bulk contraction in the
cured resin, which accumulates as the part is fabricated layer-by-layer. The degree of
shrinkage is a direct measure of the number of covalent bonds formed. Thus, shrinkage in
LAMP is characterized by estimating the number of covalent bonds formed during the
photopolymerization reaction.
Polymerization shrinkage and accompanying stresses developed during
photopolymerization of ceramic particle-loaded resins in LAMP can cause deviations
from the desired geometry. The extent of deviations depends on the photoinitiator
concentration, the filler loading, the degree of monomer conversion, and the operating
parameters such as energy dose. An understanding of shrinkage and stresses built up in a
part can assist in developing source geometry compensation algorithms and exposure
strategies to alleviate these effects. In this thesis, an attempt has been made to understand
the curing kinetics of the reaction and its relation to the polymerization shrinkage. Realtime
Fourier Transform Infrared Spectroscopy (RTFTIR) is used to determine the
conversion of monomers into polymer networks by analyzing the changes in the chemical
bonds of the participating species of molecules. The conversion data can further be used
to estimate the curing kinetics of the reaction and the relative volumetric shrinkage strain
due to polymerization.
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Técnicas de holografia computacional usando moduladores espaciais de luz aplicadas em fotolitografia sem máscaraMarinheiro, Ricardo Fonte January 2017 (has links)
Orientador: Prof. Dr. Marcos Roberto da Rocha Gesualdi / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2017. / Estudos da aplicação de moduladores espaciais de luz do tipo LCoS (Liquid Cristal
on Silicon) e técnicas holográficas em substituição às máscaras no processo de
fotolitografia são apresentados. Hologramas Gerados por Computador (HGC) a partir
de duas imagens com dimensões conhecidas, simulando uma máscara de campo
claro e uma máscara de campo escuro, foram aplicados a um modulador espacial de
luz LCoS conectado a um arranjo óptico capaz de reduzir as imagens reconstruídas,
permitindo o levantamento dos parâmetros de maior relevância no processo de
fotolitografia para fabricação de estruturas micrométricas e, a partir da sua
caracterização, identificar os limites impostos pelo modulador espacial de luz LCoS
nesse processo. Registro das imagens, com diferentes dimensões, adquiridas à
partir da reconstrução dos HGC provenientes das máscaras de campo claro e
campo escuro, foram realizados através de uma câmera CCD e filmes de alta
resolução. Os resultados permitiram a visualização e medição de estruturas com até
13 Pm e representam uma base de estudo na busca de alternativas para
substituição das máscaras em processos de fotolitografia / Application studies of the Spatial Light Modulators LCoS type (Liquid Crystal on
Silicon) and holographic techniques to replace the masks in the photolithography
process are presented. Computer-generated Holograms (HGC) from two images with
known dimensions, simulating a clear field mask and a dark field mask, were applied
to a Spatial Light Modulators LCoS connected to an optical arrangement capable of
reducing the reconstructed images, allowing the survey of the parameters of greater
relevance in the process of photolithography to fabricate micrometric structures and
from its characterization to identify the limits imposed by the Spatial Light Modulators
LCoS in this process. Recording of the images, with different dimensions, acquired
from the reconstruction of the HGC from clear field and dark field masks, were
performed through a CCD camera and high resolution films. The results allowed the
visualization and measurement of structures up to 13 ìm and represent a base of
study in the search of alternatives for replacing the masks in photolithography
processes.
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Micropatterned Photoalignment for Wavefront Controlled Switchable Optical DevicesGlazar, Nikolaus 26 April 2016 (has links)
No description available.
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