Birefringent microstructures fabricated by two-photon polymerization containing an azopolymer

Birefringent materials have many applications in optical devices. An approach to obtain optically induced birefringence is to employ a guesthost strategy, using a polymer matrix containing an azodye. However, such method normally leads to low residual birefringence. Therefore, methodologies to produce microstructures with optimized birefringence are still on demand. Here we report on the fabrication, using two-photon polymerization, and characterization of birefringent microstructures produced in a polymer blend containing an azopolymer. Such microstructures present good structural integrity and residual birefringence of approximately 35 percent, depending on the sample formulation used, which indicates this approach for the fabrication of microoptical devices.FAPESPCNPqCAPE

Two-photon absorption photopolymerization microfabrication

Neste trabalho usamos pulsos de femtossegundos na fabricação de estruturas poliméricas em escala microscópica, através da técnica de fotopolimerização via absorção de dois fótons. Graças ao confinamento espacial da polimerização, resultante do processo de absorção de dois fótons, este método permite a fabricação de microestruturas tridimensionais complexas, com alta resolução, visando diversas aplicações tecnológicas, de fotônica até biologia. Inicialmente, desenvolvemos a técnica de fotopolimerização via absorção de dois fótons, desde a implantação da montagem óptica até a confecção dos sistemas de movimentação e controle do posicionamento do feixe laser. Através da fabricação e caracterização de microestruturas, produzidas em resinas acrílicas, o sistema foi aperfeiçoado permitindo a produção de microestruturas da pordem de 30um com razoável resolução espacial. Uma vez que a maior parte as microestruturas reportadas na literatura são elementos passivos, ou seja, suas propriedades ópticas não podem ser controladas por meios externos, numa segunda etapa deste projeto produzimos microestruturas opticamente ativas. Neste caso, a microfabricação foi feita em resinas acrílicas dopadas Rodamina B, exibindo, portanto, fluorescência quando excitadas com luz de comprimento de onda em torno de 540nm. Finalmente, visando a produção eficiente de estruturas em escala milimétrica para aplicações biológicas, implementamos também um sistema de fotopolomerização via absorção de um fóton.In this work we used femtosecond pulses to fabricate polymeric structures at microscopic scale, by using the two-photon photopolymerization technique. Due to the spatial confinement of the polymerization, provided by the two-photon absorption, this method allows for the fabrication of complex three-dimensional microstructures, with high resolution, aiming to several technological applications, from photonics to biology. Initially, we developed the two-photon polimerization technique, from the optical setup to the mechanical systems to control the movement and the positioning of the laser beam. Through the fabrication and characterization os microestrutures, produced in acrylic resin, the apparatus was improved, allowing the fabriation of 30-um microstructures with reasonable spatial resolution. Since most the report in the literature are passive elements that is, their optical properties cannot be altered by any external means, in a second stage of this project we fabricated optical active microstructures. In this case, the microfabrication was carried out in acrylic resins doped with Rodamine B, exhibiting, consenquently, fluorescence when excited with light at 540nm. Finally, in order to eficiently produce milimetric structures for biological applications, we also implemented a one-photon polimerization setup

Fabrication of optically active polymeric microstructures integrated with glass nanofibers

Este trabalho demonstra o uso da fotopolimerização via absorção de dois fótons na produção de microestruturas dopadas com compostos orgânicos e nanopartículas de Au. A capacidade de produção de microestruturas com propriedades variadas é extremamente relevante, pois viabiliza o desenvolvimento de uma nova geração de dispositivos ópticos. Além disso, realizamos a conexão entre as microestruturas fabricadas e fontes de excitação, por meio de nanofibras de vidro. A integração entre essas estruturas, e destas com meios externos de excitação e detecção, é um passo essencial para o desenvolvimento de microcircuitos fotônicos, que podem representar uma nova revolução tecnológica, a exemplo do que foram os microcircuitos eletrônicos. Exploramos as possibilidades de dopagem da resina usando: (i) um composto fluorescente, (ii) um composto com birrefringência fotoinduzida e (iii) nanopartículas de ouro. Microestruturas contendo Rodamina B apresentaram boa integridade estrutural e fluorescência, tendo sido usadas para demonstrar a conexão dos microelementos com meios externos de excitação. Através de nanofibras e de micromanipuladores, comprovamos a capacidade de excitação seletiva de microestruturas através do guiamento da luz de um laser de Ar+. Estruturas birrefringentes foram obtidas pela dopagem com o azopolímero HEMA-DR13. Montamos um aparato que permite a observação da dinâmica de indução de birrefringência nas microestruturas, o qual representa um grande passo na caracterização deste tipo de microelementos. Com base nesse estudo, foi possível alcançar uma fração de birrefringência residual nas microestruturas de 35%. Por fim, propomos um método para a dopagem de microestruturas poliméricas com nanopartículas de ouro. Por se tratar de um método de dopagem indireta, ele evita interferências das nanopartículas no processo de microfabricação. Dessa forma, este trabalho abre possibilidades para a fabricação de microdispositivos funcionais com diversas propriedades especiais, bem como a integração desses microdispositivos em circuitos fotônicos.This work demonstrates the use of two-photon photopolymerization in the fabrication of microstructures doped with organic compounds and gold nanoparticles. The ability to produce microstructures with different properties is extremely relevant, because it opens the possibility for the development of a new generation of optical devices. Besides, we have accomplished the connection between fabricated microstructures and excitation sources by means of silica nanowires. The connection among structures and with external means of detection and excitation is an essential step towards the development of new technological breakthrough in photonic microcircuits. We have explored the resin doping possibilities by using: (i) a fluorescent compound, (ii) a photoinduced birefringent compound and (iii) gold nanoparticles. Rhodamine B doped microstructures present good structural integrity and fluorescence, and were able to demonstrate the connection of microelements with external means of excitation. Through the use of nanofiber tapers and micromanipulators, we have shown the selective excitation capability of this method by guiding Ar+ laser light onto one single microstructure. Birefringent samples were obtained by doping the resin with the azopolymer HEMA-DR13. We have assembled an apparatus that allows observing the photoinduced birefringence dynamics, which represents a great step towards a better characterization of these kinds of microelements. Based on this study we were able to achieve a residual birefringence fraction of 35% in microscopic samples. Finally, we have proposed a new method for the doping of polymeric microstructures with gold nanoparticles. Because it is an indirect doping technique, it prevents gold nanoparticles from interfering with the microfabrication process. Thus, the work presented here paves the way for the fabrication of functional microdevices with a wide range of special properties, as well as for the connection of these microstructures for photonic microcircuit

Femtosecond Laser in Polymeric Materials: Microfabrication of Doped Structures and Micromachining

The use of laser light to modify the material's surface or bulk as well as to induce changes in the volume through a chemical reaction has received great attention in the last few years, due to the possibility of tailoring the material's properties aiming at technological applications. Here, we report on recent progress of microstructuring and microfabrication in polymeric materials by using femtosecond lasers. In the first part, we describe how polymeric materials' micromachining, either on the surface or bulk, can be employed to change their optical and chemical properties promising for fabricating waveguides, resonators, and self-cleaning surfaces. In the second part, we discuss how two-photon absorption polymerization can be used to fabricate active microstructures by doping the basic resin with molecules presenting biological and optical properties of interest. Such microstructures can be used to fabricate devices with applications in optics, such as microLED, waveguides, and also in medicine, such as scaffolds for tissue growth.Fundacao a Pesquisa do Estado de Sao PauloFundacao a Pesquisa do Estado de Sao PauloConselho Nacional de Desenvolvimento Cientifico e TecnologicoConselho Nacional de Desenvolvimento Cientifico e TecnologicoCoordenacao de Aperfeicoamento de Pessoal de Nivel SuperiorCoordenacao de Aperfeicoamento de Pessoal de Nivel Superio

Selective excitation through tapered silica fibers of fluorescent two-photon polymerized structures

Two-photon polymerization has emerged as a powerful tool to design complex three-dimensional microstructures for applications ranging from biology to nanophotonics. To broaden the application spectrum of such microstructures, different materials have been incorporated to the polymers, aiming at specific applications. In this paper we report the fabrication of microstructures containing rhodamine 610, which display strong fluorescence upon one- and two-photon excitation. The latter increases light-penetration depth and spatial selectivity of luminescence. We also demonstrate that by using silica submicrometric wires we were able to select individual microstructures to be excited, which could be explored for designing microstructure-based optical circuits.FAPESPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPqCAPES from BrazilCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Air Force Office of Scientific Research (AFOSR) [FA9550-07-1-0374]U.S. Air Force Office of Scientific Research (AFOSR

Indirect doping of microstructures fabricated by two-photon polymerization with gold nanoparticles

Nanoplasmonics and metamaterials sciences are rapidly growing due to their contributions to photonic devices fabrication with applications ranging from biomedicine to photovoltaic cells. Noble metal nanoparticles incorporated into polymer matrix have great potential for such applications due to their distinctive optical properties. However, methods to indirectly incorporate metal nanoparticles into polymeric microstructures are still on demand. Here we report on the fabrication of two-photon polymerized microstructures doped with gold nanoparticles through an indirect doping process, so they do not interfere in the two-photon polymerization (2PP) process. Such microstructures present a strong emission, arising from gold nanoparticles fluorescence. The microstructures produced are potential candidates for nanoplasmonics and metamaterials devices applications and the nanoparticles production method can be applied in many samples, heated simultaneously, opening the possibility for large scale processes.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Indirect doping of microstructures fabricated by two-photon polymerization with gold nanoparticles

Nanoplasmonics and metamaterials sciences are rapidly growing due to their contributions to photonic devices fabrication with applications ranging from biomedicine to photovoltaic cells. Noble metal nanoparticles incorporated into polymer matrix have great potential for such applications due to their distinctive optical properties. However, methods to indirectly incorporate metal nanoparticles into polymeric microstructures are still on demand. Here we report on the fabrication of two-photon polymerized microstructures doped with gold nanoparticles through an indirect doping process, so they do not interfere in the two-photon polymerization (2PP) process. Such microstructures present a strong emission, arising from gold nanoparticles fluorescence. The microstructures produced are potential candidates for nanoplasmonics and metamaterials devices applications and the nanoparticles production method can be applied in many samples, heated simultaneously, opening the possibility for large scale processes. (C) 2012 Optical Society of AmericaFAPESPFAPESPCNPqCNPqCAPES from BrazilCAPES from Brazi

Fabrication of Zinc Oxide Nanowires/Polymer Composites by Two-Photon Polymerization

We present an approach to fabricate ZnO nanowires/polymer composite into three-dimensional microstructures, based on two-photon polymerization direct laser writing, a fabrication method that allows submicrometric spatial resolution. The structural integrity of the structures was inferred by scanning electron microscopy, while the presence and distribution of ZnO nanowires was investigated by energy dispersive X-ray, Raman spectroscopy, and X-ray diffraction. The optical properties of the produced composite microstructures were verified by imaging the characteristic ZnO emission using a fluorescence microscope. Hence, such approach can be used to develop composite microstructures containing ZnO nanowires aiming at technological applications. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 333-337Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Electrochemical Sensitivity Improvement by the Cooperation between Pt and Ru for Total Antioxidant Evaluation in Natural Extracts

Herein, a straightforward electrochemical method was used to evaluate the total phenolic antioxidant capacity in natural extracts prepared from pomegranate, hibiscus, and pitaya. In light of this, the well-known electrochemical index (EI), a screening protocol for natural antioxidant properties evaluation, was determined using differential pulse voltammetry. Initially considering rutin and catechin as standards, we found that the system’s sensitivity greatly increased by using platinum (Pt) and platinum/ruthenium (Pt/Ru) nanoparticles (NPs) immobilized on Vulcan XC-72 to modify screen-printed carbon electrodes (SPCEs). When such modifications were applied to natural fruit/plant extracts, their electrochemical ability proved highly superior to the bare SPCE, even considering a very small amount of materials for electrode preparation. However, with an optimized ratio, the bimetallic counterpart was more sensitive to detection. When the pomegranate extract was used, for example, EI values of 52.51 ± 6.00 and 104.79 ± 6.89 µA/V were obtained using Pt and Pt/Ru (with an optimized ratio) electrocatalysts, showing the remarkable sensitivity increase obtained in our bimetallic protocol. Thus, based on physicochemical and electrochemical characterizations, we found that the ruthenium content was essential for the achievements. In due course, XPS analysis suggested that the Pt2+/Pt0 species ratio could have improved the system’s sensitivity, which significantly changed when ruthenium was used in the material