Processamento de superfícies poliméricas com pulsos laser de nano e femtossegundos 

Abstract

comportamento de molhamento anisotrópico. De maneira geral, os resultados aqui apresentados, além de demonstrar a potencialidade das técnicas de microfabricação a laser, fornecem importantes informações sobre os parâmetros ótimos para microfabricação em filmes poliméricos, visando aplicações tanto em dispositivos fotônicos e optoeletrônicos quanto em biomateriais. Palavras chave: Microestruturação. Polímeros. Ablação. Modificação de superfícies. Materiais implantáveis. ABSTRACT Alves, R. E. Polymeric surfaces processing with nano-and femtosecond laser pulses. 2015. 106p. Thesis (doctorate) -São Carlos School of Engineering, University of São Paulo, São Paulo, 2015.In this work we explored the use of laser micromachining methods to structure polymeric materials, aiming to obtain surfaces that can be applied in the development of photonic devices as well as biomedical materials. Firstly, we investigated the influence of pulse energy and translation speed on microstructures fabricated on the surface of poly[2-methoxy-5-(2'ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) films. We observed that the roughness of the microstructured surface significantly increased with the pulse energy and translation speed.Besides, we determined the energy threshold for material removal, distinguishing the energy range for polymer removal from that causing only structural changes. Once the proper laser micromachining conditions were determined, we were able to apply such approach to fabricate a functional microstructured electroluminescent device, without disrupting the indium tin oxide layer used as the contact for the devices. In the second part of the work, we studied the influence of femtosecond pulses on the structuring process of chitosan films. In this case, we determined the threshold energy that leads to structural change and material removal. We have been able to produced microstructures with hydrophilic characteristics, in addition to surfaces with different structuring that were used to study the formation of Staphylococcus aureus biofilm.For such purpose we produced microstructured areas of 500 μm 2 and different periods (ranging from 4 to 12 µm) on the surface of chitosan and poly(methyl methacrylate)(PMMA) films. With these microstructures we observed different behaviors in the biofilm formation; in the case of PMMA, there was not distinction of development; concerning the chitosan samples we observed preferential bacterial growth on the rougher regions of the microstructures. Lastly, in a third part of the study, we used the method of direct laser interference patterning to fabricate periodic microstructures on polyurethane membranes, using nanosecond pulses. With this method, we produced high quality microstructures on the surface of polyurethane with different periodicity (from 500 nm to 5.0 um). This approach allowed obtaining samples with anisotropic wetting behavior. In general, the results presented here, in addition to demonstrating the potential of the laser micromachining methods to structure polymeric samples, p...

Desenvolvimento de uma ferramenta mobile para teste Elisa em microcircuitos e detecção de cores com inteligência artificial

“…Sua aplicação é realmente muito ampla, passando por áreas como robótica, engenharia de materiais e biotecnologia, utilizando combinações de técnicas como fluorescência, mapeamento de imagens dinâmica dos fluidos e várias outras 8,[24][25][26][27][28] .…”

“…Essa técnica apresenta várias vantagens quando comparada a outras abordagens, sendo um método de processamento direto, de um único passo e sem máscara 7 . A utilização de laser de femtossegundos é defendida pela característica de não criar uma zona térmica no alvo, diminuindo a onda de choque, que pode ultrapassar a espessura do material 7,8 .…”