Fabrication of micro-structures for optically driven micromachines using two-photon photopolymerization of UV curing resins

Two-photon photopolymerization of UV curing resins is an attractive method for the fabrication of microscopic transparent objects with size in the tens of micrometers range. We have been using this method to produce three-dimensional structures for optical micromanipulation, in an optical system based on a femtosecond laser. By carefully adjusting the laser power and the exposure time we were able to create micro-objects with well-defined 3D features and with resolution below the diffraction limit of light. We discuss the performance and capabilities of a microfabrication system, with some examples of its products.Comment: 12 pages, 10 figure

Characterization of optically driven fluid stress fields with optical tweezers

We present a controlled stress microviscometer with applications to complex fluids. It generates and measures microscopic fluid velocity fields, based on dual beam optical tweezers. This allows an investigation of bulk viscous properties and local inhomogeneities at the probe particle surface. The accuracy of the method is demonstrated in water. In a complex fluid model (hyaluronic acid), we observe a strong deviation of the flow field from classical behavior. Knowledge of the deviation together with an optical torque measurement is used to determine the bulk viscosity. Furthermore, we model the observed deviation and derive microscopic parameters

Theory and practice of computational modeling and simulation of optical tweezers

In theory, there is no difference between theory and practice, but, in practice, there is. While a diverse range of theoretical options exist, practical considerations play a major role in choosing which to use

IMPLICAÇÕES DO REUSO DE EFLUENTE DE ESGOTO DOMÉSTICO TRADADO NA IRRIGAÇÃO AGRÍCOLA

A agricultura irrigada torna-se cada vez mais necessária para suprir a carência de produção alimentar no mundo. A irrigação com efluente na subsuperfície do solo pode ser considerada como mais um tratamento no efluente de esgoto. Ao aplicar o efluente no solo agrícola, além se disponibilizar água e nutrientes às raízes das plantas, ainda se oferece maior segurança de sanidade nos cultivos e se permite direcionar a água de melhor qualidade a consumo doméstico. Diante de tal realidade, buscou-se considerar a pratica do reuso de água para a irrigação como uma forma viável de suprir tal necessidade. Foi utilizado um estudo bibliográfico exploratório de diversas fontes, onde resultados e discussões de pesquisas antigas e recentes são analisados. O texto permite discutir e subsidiar o leitor em relação às implicações da prática do reuso de água no meio ambiente. A perspectiva é que em meio a crise hídrica o reuso possa trazer sustentabilidade e, aumentar a produção de alimento e energia ao mundo

Measurement of refractive index of single microparticles

The refractive index of single microparticles is derived from precise measurement and rigorous modeling of the stiffness of a laser trap. We demonstrate the method for particles of four different materials with diameters from 1.6 to 5.2 microns and achieve an accuracy of better than 1%. The method greatly contributes as a new characterization technique because it works best under conditions (small particle size, polydispersion) where other methods, such as absorption spectroscopy, start to fail. Particles need not be transferred to a particular fluid, which prevents particle degradation or alteration common in index matching techniques. Our results also show that advanced modeling of laser traps accurately reproduces experimental reality

CRESCIMENTO DE AMARANTHUS SP. E GALINSOGA PARVIFLORA EM CULTIVO DE CARTHAMUS TINCTORIUS IRRIGADO E SOB SEQUEIRO

Este trabalho teve como objetivo avaliar efeitos do déficit hídrico no crescimento de Amaranthus sp. e Galinsoga parviflora em cultivo de Carthamus tinctorius na fase vegetativa de crescimento em solo de textura arenosa. O experimento foi conduzido em estação seca de outono no município de Engenheiro Coelho, SP. O cultivo de cártamo pode ser considerado como uma alternativa de cultivo energético para períodos secos. Adotou-se delineamento inteiramente casualizado em tratamentos irrigado e com déficit hídrico com quatro repetições. Foram avaliadas duas espécies de plantas daninhas aos 30 dias após o plantio: Amatranthus sp. e Galinsoga parviflora. As características avaliadas foram: altura de plantas, número de folhas, diâmetro e comprimento do caule, comprimento da raiz, massa fresca da planta, massa fresca das folhas, massa fresca do caule com raiz e área foliar. Os resultados permitem concluir que: as variáveis morfológicas avaliadas nas duas espécies de plantas daninhas foram influenciadas pela disponibilidade de água no solo nos primeiros 30 dias de crescimento do cártamo. &nbsp

Symmetry and the generation and measurement of optical torque

A key element in the generation of optical torque in optical traps, which occurs when electromagnetic angular momentum is transferred from the trapping beam to the trapped particle by scattering, is the symmetries of the scattering particle and the trapping beam. We discuss the effect of such symmetries on the generation and measurement of optical torque in optical tweezers, and some consequent general principles for the design of optically-driven micromachines.Comment: 28 page

Orbital Angular Momentum (OAM) of Rotating Modes Driven by Electrons in Electron Cyclotron Masers

The well-defined orbital angular momentum (OAM) of rotating cavity modes operating near the cutoff frequency excited by gyrating electrons in a high-power electron cyclotron maser (ECM)-a gyrotron-has been derived by photonic and electromagnetic wave approaches. A mode generator was built with a high-precision 3D printing technique to mimic the rotating gyrotron modes for precise low-power measurements and shows clear natural production of higher-order OAM modes. Cold-test measurements of higher-order OAM mode generation promise the realization towards wireless long-range communications using high-power ECMs