Bessel beams from semiconductor light sources

We report on recent progress in the generation of non-diffracting (Bessel) beams from semiconductor light sources including both edge-emitting and surface-emitting semiconductor lasers as well as light-emitting diodes (LEDs). Bessel beams at the power level of Watts with central lobe diameters of a few to tens of micrometers were achieved from compact and highly efficient lasers. The practicality of reducing the central lobe size of the Bessel beam generated with high-power broad-stripe semiconductor lasers and LEDs to a level unachievable by means of traditional focusing has been demonstrated. We also discuss an approach to exceed the limit of power density for the focusing of radiation with high beam propagation parameter M2. Finally, we consider the potential of the semiconductor lasers for applications in optical trapping/tweezing and the perspectives to replace their gas and solid-state laser counterparts for a range of implementations in optical manipulation towards lab-on-chip configurations. © 2014 Elsevier Ltd.

Optical trapping with superfocused high-M2 laser diode beam

Many applications of high-power laser diodes demand tight focusing. This is often not possible due to the multimode nature of semiconductor laser radiation possessing beam propagation parameter M2 values in double-digits. We propose a method of 'interference' superfocusing of high-M2 diode laser beams with a technique developed for the generation of Bessel beams based on the employment of an axicon fabricated on the tip of a 100 μm diameter optical fiber with highprecision direct laser writing. Using axicons with apex angle 140º and rounded tip area as small as 10 μm diameter, we demonstrate 2-4 μm diameter focused laser 'needle' beams with approximately 20 μm propagation length generated from multimode diode laser with beam propagation parameter M2=18 and emission wavelength of 960 nm. This is a few-fold reduction compared to the minimal focal spot size of 11 μm that could be achieved if focused by an 'ideal' lens of unity numerical aperture. The same technique using a 160º axicon allowed us to demonstrate few-μm-wide laser 'needle' beams with nearly 100 μm propagation length with which to demonstrate optical trapping of 5-6 μm rat blood red cells in a water-heparin solution. Our results indicate the good potential of superfocused diode laser beams for applications relating to optical trapping and manipulation of microscopic objects including living biological objects with aspirations towards subsequent novel lab-on-chip configurations.

Chemiluminescence DNA-based Nanotechnologies for Bioanalytical Applications

DNA as powerful building molecule, is widely used for the assembly of molecular structures and dynamic molecular devices with different potential applications, ranging from synthetic biology to diagnostics. The feature of sequence programmability, which makes it possible to predict how single stranded DNA molecules fold and interact with one another, allowed the development of spatiotemporally controlled nanostructures and the engineering of supramolecular devices. The first part of this thesis addresses the development of an integrated chemiluminescence (CL)-based lab-on-chip sensor for detection of Adenosine-5-triphosphate (ATP) life biomarker in extra-terrestrial environments.Subsequently, we investigated whether it is possible to study the interaction and the recognition between biomolecules and their targets, mimicking the intracellular environment in terms of crowding, confinement and compartmentalization. To this purpose, we developed a split G-quadruplex DNAzyme platform for the chemiluminescent and quantitative detection of antibodies based on antibody-induced co-localization proximity mechanism in which a split G-quadruplex DNAzyme is led to reassemble into the functional native G-quadruplex conformation as the effect of a guided spatial nanoconfinement.The following part of this thesis aims at developing chemiluminescent nanoparticles for bioimaging and photodynamic therapy applications.In chapter5 a realistic and accurate evaluation of the potentiality of electrochemistry and chemiluminescence (CL) for biosensors development (i.e., is it better to “measure an electron or a photon”?), has been achieved.In chapter 6 the emission anisotropy phenomenon for an emitting dipole bound to the interface between two media with different refractive index has been investigated for chemiluminescence detection.

Chemiluminescence – based bioanalytical devices for astrobiological, food safety and clinical applications

At the intersection of biology, chemistry, and engineering, biosensors are a multidisciplinary innovation that provide a cost-effective alternative to traditional laboratory techniques. Due to their advantages, biosensors are used in medical diagnostics, environmental monitoring, food safety and many other fields. The first part of the thesis is concerned with learning the state of the art of paper-based immunosensors with bioluminescent (BL) and chemiluminescent (CL) detection. The use of biospecific assays combined with CL detection and paper-based technology offers an optimal approach to creating analytical tools for on-site applications and we have focused on the specific areas that need to be considered more in order to ensure a future practical implementation of these methods in routine analyses. The subsequent part of the thesis addresses the development of an autonomous lab-on-chip platform for performing chemiluminescent-based bioassays in space environment, exploiting a CubeSat platform for astrobiological investigations. An origami-inspired microfluidic paper-based analytical device has been developed with the purpose of assesses its performance in space and to evaluate its functionality and the resilience of the (bio)molecules when exposed to a radiation-rich environment. Subsequently, we designed a paper-based assay to detect traces of ovalbumin in food samples, creating a user-friendly immunosensing platform. To this purpose, we developed an origami device that exploits a competitive immunoassay coupled with chemiluminescence detection and magnetic microbeads used to immobilize ovalbumin on paper. Finally, with the aim of exploring the use of biomimetic materials, an hydrogel-based chemiluminescence biosensor for the detection of H2O2 and glucose was developed. A guanosine hydrogel was prepared and loaded with luminol and hemin, miming a DNAzyme activity. Subsequently, the hydrogel was modified by incorporating glucose oxidase enzyme to enable glucose biosensing. The emitted photons were detected using a portable device equipped with a smartphone's CMOS (complementary metal oxide semiconductor) camera for CL emission detection.

Brittle and ductile removal modes observed during diamond turning of carbon nanotube composites

Ultraprecision diamond turning was used to evaluate the surface integrity of a carbon nanotube (CNT) composite as a function of the cutting conditions and the percentage of CNT in the epoxy matrix. The effects of cutting conditions on the chip morphology and surface roughness were analysed. The results showed that an increase in the percentage of CNT may influence the mechanism of material removal and consequently improve the quality of the machined surface. When smaller quantities of CNT (0.02 and 0.07 wt %) are present in the matrix, microcracks form within the cutting grooves (perpendicular to the cutting direction). This indicates that the amount of CNT on the epoxy matrix may have a direct influence on the mechanical properties of these materials. Chips removed from the CNT composite samples were analysed by scanning electron microscopy in order to correlate the material removal mechanism and the surface generation process. The area average surface roughness Sa was influenced by the material removal mechanism (Sa ranging from 0.28 to 1.1 mu m).

Downscaling a multicommuted flow injection analysis system for the photometric determination of iodate in table salt

In this work a downscaled multicommuted flow injection analysis setup for photometric determination is described. The setup consists of a flow system module and a LED based photometer, with a total internal volume of about 170 mu L The system was tested by developing an analytical procedure for the photometric determination of iodate in table salt using N,N-diethyl-henylenediamine (DPD) as the chromogenic reagent. Accuracy was accessed by applying the paired r-test between results obtained using the proposed procedure and a reference method, and no significant difference at the 95% confidence level was observed. Other profitable features, such as a low reagent consumption of 7.3 mu g DPD per determination: a linear response ranging from 0.1 up to 3.0 m IO(3)(-), a relative standard deviation of 0.9% (n = 11) for samples containing 0.5 m IO(3)(-), a detection limit of 17 mu g L(-1) IO(3)(-), a sampling throughput of 117 determination per hour, and a waste generation 600 mu L per determination, were also achieved. (C) 2010 Elsevier B.V. All rights reserved.

Sistema de contagem de tráfego e classificação automática de veículos, em tempo real e sem fios

Esta tese tem por objectivo o desenho e avaliação de um sistema de contagem e classificação de veículos automóveis em tempo-real e sem fios. Pretende, também, ser uma alternativa aos actuais equipamentos, muito intrusivos nas vias rodoviárias. Esta tese inclui um estudo sobre as comunicações sem fios adequadas a uma rede de equipamentos sensores rodoviários, um estudo sobre a utilização do campo magnético como meio físico de detecção e contagem de veículos e um estudo sobre a autonomia energética dos equipamentos inseridos na via, com recurso, entre outros, à energia solar. O projecto realizado no âmbito desta tese incorpora, entre outros, a digitalização em tempo real da assinatura magnética deixada pela passagem de um veículo, no campo magnético da Terra, o respectivo envio para servidor via rádio e WAN, Wide Area Network, e o desenvolvimento de software tendo por base a pilha de protocolos ZigBee. Foram desenvolvidas aplicações para o equipamento sensor, para o coordenador, para o painel de controlo e para a biblioteca de Interface de um futuro servidor aplicacional. O software desenvolvido para o equipamento sensor incorpora ciclos de detecção e digitalização, com pausas de adormecimento de baixo consumo, e a activação das comunicações rádio durante a fase de envio, assegurando assim uma estratégia de poupança energética. Os resultados obtidos confirmam a viabilidade desta tecnologia para a detecção e contagem de veículos, assim como para a captura de assinatura usando magnetoresistências. Permitiram ainda verificar o alcance das comunicações sem fios com equipamento sensor embebido no asfalto e confirmar o modelo de cálculo da superfície do painel solar bem como o modelo de consumo energético do equipamento sensor.

Sistema de multiprocessamento para simulação de N-corpos em FPGA

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia de Electrónica e Telecomunicações

Many-core approach to 2D-DCT calculation using an FPGA

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia de Electrónica e Telecomunicações

Conceção de um tutorial de Iniciação ao co-projeto de Hardware/software

A crescente evolução dos dispositivos contendo circuitos integrados, em especial os FPGAs (Field Programmable Logic Arrays) e atualmente os System on a chip (SoCs) baseados em FPGAs, juntamente com a evolução das ferramentas, tem deixado um espaço entre o lançamento e a produção de materiais didáticos que auxiliem os engenheiros no Co- Projecto de hardware/software a partir dessas tecnologias. Com o intuito de auxiliar na redução desse intervalo temporal, o presente trabalho apresenta o desenvolvimento de documentos (tutoriais) direcionados a duas tecnologias recentes: a ferramenta de desenvolvimento de hardware/software VIVADO; e o SoC Zynq-7000, Z-7010, ambos desenvolvidos pela Xilinx. Os documentos produzidos são baseados num projeto básico totalmente implementado em lógica programável e do mesmo projeto implementado através do processador programável embarcado, para que seja possível avaliar o fluxo de projeto da ferramenta para um projeto totalmente implementado em hardware e o fluxo de projeto para o mesmo projeto implementado numa estrutura de harware/software.

Desenvolvimento de microfluídica em papel para utilização em biossensores

Dissertação para obtenção do Grau de Mestre em Engenharia Biomédica

Desenvolvimento de dispositivos microfluídicos 3D em papel para utilização em biossensores

Dissertação para obtenção do Grau de Mestre em Engenharia Biomédica

Desenvolvimento de um teste de diagnóstico rápido para a deteção de malária em amostras clínicas

A malária é uma doença infeciosa transmitida através da picada de um mosquito fêmea Anopheles infetado com o parasita protozoário do género Plasmodium (P.), sendo o P. falciparum a espécie mais mortal. É responsável pela morte de milhares de pessoas por ano, nomeadamente nos países em vias desenvolvimento, países esses que não detêm as condições necessárias para a prática da microscopia ótica em larga escala, que continua nos dias de hoje a ser a técnica de eleição para o diagnóstico da doença. A conceção de testes de baixo custo e de fácil utilização tais como os testes de diagnóstico rápido (TDR) são uma mais-valia no diagnóstico deste tipo de doenças. A presente dissertação centra-se no desenvolvimento de um TDR num formato competitivo, baseado em nanopartículas de ouro (AuNP) funcionalizadas com ácido mercaptoundecanoico (MUA) ou com o pentapétido Cys-Ala-Leu-Asn-Asn (CALNN) e conjugadas com um anticorpo monoclonal anti-PfHRP2 que reconhece especificamente a proteína rica em histidina 2 produzida pelo P. falciparum (PfHRP2). Para isso, utilizou-se uma tecnologia inovadora na conceção do TDR, a tecnologia lab on paper, que utiliza o papel Whatman nº1. Os estudos de estabilidade de AuNP funcionalizadas com citrato de sódio, MUA ou CALNN por variação da força iónica e pH do meio mostraram que o pentapéptido CALNN é o agente de revestimento mais resistente a oscilações de força iónica, comparativamente com o citrato de sódio e o MUA e que apenas as AuNP revestidas com citrato de sódio atingiram o ponto de agregação ao pKa da molécula de revestimento. Os principais resultados obtidos aquando do desenvolvimento do TDR revelaram que o valor de diluição ótima de anticorpo anti-IgG (solução mãe a 11 mg.mL-1) imobilizado na linha de controlo é de 1:40 e 1:90, utilizando para deteção os bionanoconjugados AuNP-MUA-Anticorpo e AuNP-CALNN-Anticorpo, respetivamente. Com a aplicação da solução AuNP-CALNN-Anticorpo visualizou-se o aparecimento de cor vermelha na linha de teste, o que demonstra a deteção do antigénio pelos bionanoconjugados. A deteção ocorreu com a aplicação de 2,5 μL de PfHRP2 a 1,5 mg.mL-1. Numa análise global após a aplicação de culturas de sangue não infetadas ou infetadas com o parasita da malária, obteve-se cor na linha de controlo com uma diluição de 1:20 do anticorpo anti-IgG imobilizado. Em relação à linha de teste, na presença de culturas não infetadas, obteve-se sinal na mesma aplicando bionanoconjugados AuNP-MUA-Anticorpo e 2,5 μL de PfHRP2 a 2,6 mg.ml-1.

Creació d'IP Cores en una plataforma NIOS: metodologia de disseny

NIOS és el processador que Altera empra en els seus dissenys SOC (System On Chip). Per tal de facilitar-ne el seu ús, Altera també proporciona una plataforma de desenvolupament SOPC (System On Programable Chip) que agilitza enormement el disseny d’aquests sistemes. Així doncs, aquest projecte està centrat en la definició metodològica per a la creació d'IP Cores en una plataforma NIOS.

The trail making test as a screening instrument for driving performance in older drivers; a translational research.

BACKGROUND: In many countries, primary care physicians determine whether or not older drivers are fit to drive. Little, however, is known regarding the effects of cognitive decline on driving performance and the means to detect it. This study explores to what extent the trail making test (TMT) can provide indications to clinicians about their older patients' on-road driving performance in the context of cognitive decline. METHODS: This translational study was nested within a cohort study and an exploratory psychophysics study. The target population of interest was constituted of older drivers in the absence of important cognitive or physical disorders. We therefore recruited and tested 404 home-dwelling drivers, aged 70 years or more and in possession of valid drivers' licenses, who volunteered to participate in a driving refresher course. Forty-five drivers also agreed to undergo further testing at our lab. On-road driving performance was evaluated by instructors during a 45 minute validated open-road circuit. Drivers were classified as either being excellent, good, moderate, or poor depending on their score on a standardized evaluation of on-road driving performance. RESULTS: The area under the receiver operator curve for detecting poorly performing drivers was 0.668 (CI95% 0.558 to 0.778) for the TMT-A, and 0.662 (CI95% 0.542 to 0.783) for the TMT-B. TMT was related to contrast sensitivity, motion direction, orientation discrimination, working memory, verbal fluency, and literacy. Older patients with a TMT-A ≥ 54 seconds or a TMT-B ≥ 150 seconds have a threefold (CI95% 1.3 to 7.0) increased risk of performing poorly during the on-road evaluation. TMT had a sensitivity of 63.6%, a specificity of 64.9%, a positive predictive value of 9.5%, and a negative predictive value of 96.9%. CONCLUSION: In screening settings, the TMT would have clinicians uselessly consider driving cessation in nine drivers out of ten. Given the important negative impact this could have on older drivers, this study confirms the TMT not to be specific enough for clinicians to justify driving cessation without complementary investigations on driving behaviors.