Microtecnologias na UM

Comunicação apresentada no Workshop do Grupo de Revestimentos Funcionais (GRF), Braga, Dezembro 2001.A microelectrónica, estando presente numa gama extensa de produtos que vão desde as comunicações aos transportes, passando pelos sectores doméstico, industrial e militar, desempenha cada vez mais um papel fulcral na economia e no desenvolvimento. Hoje em dia é possível integrar num só circuitos funcionalidades equivalentes às de sistemas mais volumosos, o que conduz à miniaturização dos equipamentos, mais elevados níveis de fiabilidade e desempenho, e ainda à redução de custos. Nos últimos anos deu-se em paralelo com o desenvolvimento da microelectrónica o aparecimento de microtecnologias (Ex.: micromaquinagem, microlitografia, microfabricação), direccionadas para a implementação de microdispositivos (microssensores, microactuadores) no silício. muitas vezes também integrados com electrónica no mesmo substrato de silício. Estas novas tecnologias, em especial a micromaquinagem, revelam elevado potencial para o desenvolvimento de microssistemas (designação para sensores e/ou actuadores integrados com electrónica no mesmo substrato de silício). A miniaturização, o fabrico em larga escala a baixos preços e a portabilidade destas soluções despertou o interesse da indústria de que são exemplo: as telecomunicações, a indústria automóvel e as aplicações biomédicas.Fundação para a Ciência e Tecnologia

Tidal damping of the mutual inclination in hierachical systems

Hierarchical two-planet systems, in which the inner body's semi-major axis is between 0.1 and 0.5 AU, usually present high eccentricity values, at least for one of the orbits. As a result of the formation process, one may expect that planetary systems with high eccentricities also have high mutual inclinations. However, here we show that tidal effects combined with gravitational interactions damp the initial mutual inclination to modest values in timescales that are shorter than the age of the system. This effect is not a direct consequence of tides on the orbits, but it results from a secular forcing of the inner planet's flattening. We then conclude that these hierarchical planetary systems are unlikely to present very high mutual inclinations, at least as long as the orbits remain outside the Lidov-Kozai libration areas. The present study can also be extended to systems of binary stars and to planet-satellite systems.Comment: 16 pages, 13 figure

A high-performance scintillator-silicon-well x-rays microdetector based on DRIE techniques

This paper describes a X-rays detector based on an array of scintillator crystals, CsI:Tl, encapsulated in well-type silicon. The X-ray energy is first converted to visible light which is detected by a photodetector in the well bottom. DRIE techniques are used to achieve perfect vertical sidewalls 515 um deep, 100 um pixel square size and to maximize the fill factor. The inner walls of the well are electroplated with aluminum for improving the number of photons arriving in the detector and to reduce cross-talk between adjacent wells. Simulations and modeling show an improvement of approximately 26% in the detection efficiency using an aluminum layer 5 um thick

Células de carga inteligentes

Este artigo descreve a implementaçãoo de uma arquitectura de procesamento de sinal das células de carga, muito simples, bastante eficaz e de baixo custo, desenvolvida em torno de um microcontrolador RISC e tirando partido da característica ratiomérica da saída das células de carga. Para amplificaçãoo e filtragem dos sinais aplicaram-se as técnicas de condensadores comutados. A necessidade de estabilidde térmica dos circuitos e componentes é minimizada devido ao uso da mesma cadeia de amplificação para o sinal e referência em conjunto com o software de calibração. A conversão analógico-digital é feita através do método de rampa simples, sendo controlado pelo microcontrolador que realiza todo o processamento digital necessário, bem como a comunicação série com o exterior. Também é descrito um exemplo de software de calibração duma plataforma de pesagem com várias células de craga "inteligentes"

Digital filtering in smart load cells

This paper describes an application of a Self Adaptive Pseudo-Moving Average Filter used in the implementation of a Smart Load Cell, to combine a stable digital output with a fast response to weight changes. The Smart Load Cell is a data acquisition solution using a single chip RISC microcontroller with very few other active and passive components around and taking advantage of the ratiometric functioning of load cell. The use of Smart Load Cells with digital outputs needs a cost effective in digital filtering of the final converter results for each Smart Load Cell. The technique is established by theoretical analysis and is justified by means of simulation and experimental results. The paper also describes an example of software calibration of a Multi-Load-Cells weighbridge, using four smart load cells.CEL-Cachapuz Electrónica Lda

Wireless hydrotherapy smart suit for monitoring handicapped people

This paper presents a smart suit, water impermeable, containing sensors and electronics for monitoring handicapped people at hydrotherapy sessions in swimming-pools. For integration into textiles, electronic components should be designed in a functional, robust and inexpensive way. Therefore, small-size electronics microsystems are a promising approach. The smart suit allows the monitoring of individual biometric data, such as heart rate, temperature and movement of the body. Two solutions for transmitting the data wirelessly are presented: through a low-voltage (3.0 V), low-power, CMOS RF IC (1.6 mm x 1.5 mm size dimensions) operating at 433 MHz, with ASK modulation and a patch antenna built on lossy substrates compatible with integrated circuits fabrication. Two different substrates were used for antenna implementation: high-resistivity silicon (HRS) and Corning Pyrex #7740 glass. The antenna prototypes were built to operate close to the 5 GHz ISM band. They operate at a center frequency of 5.705 GHz (HRS) and 5.995 GHz (Pyrex). The studied parameters were: substrate thickness, substrate losses, oxide thickness, metal conductivity and thickness. The antenna on HRS uses an area of 8 mm2, providing a 90 MHz bandwidth and ~0.3 dBi of gain. On a glass substrate, the antenna uses 12 mm2, provides 100 MHz bandwidth and ~3 dBi of gain.Fundação para a Ciência e Tecnologia (FCT), project (SFRH/BD/4717/2001 and POCTI/ESE/38468/2001

ISO observations of M8, the Lagoon nebula

In this paper, IRAS, ISO, and molecular line observations of the M8 and M8E sources in the Lagoon Nebula are reported

RF CMOS transceiver at 2.4 GHz in wearables for measuring the cardio-respiratory function

This paper presents a radio-frequency (RF) transceiver for operation in the 2.4 GHz ISM band. The RF CMOS transceiver can be supplied with only 1.8 V, and it was designed to establish wireless links for distances up to 10 m, for a maximum baud-rate of 250 Kbps with a Bit Error Probability less than 10 6. The transmitter can deliver a output power of 0 dBm with a consumption of only 11.2 mW, while the receiver has sensitivity of 60 dBm and consumes only 6.3 mW. The goal of RF CMOS transceiver is for co-integration with sensors in the same die using microsystems techniques. The target application of such microsystems is in wearables (e.g., in wireless electronic shirts) for measuring biomedical data of patients. The wireless electronic shirt (WES) measures the heart rate and the respiratory frequency, and at the same time it allows patients to maintain their mobilit

On-chip integrated silicon bulk-micromachined soil moisture sensor based on the DPHP method

This paper reports the design, modelling, fabrication and assembly of a silicon bulk-micromachined soil moisture microsensor using the Dual-Probe Heat-Pulse (DPHP) method. Soil humidity measurement is essential to studysoil preservation and control the development of plants, namely in closed ecosystem. The DPHP method uses a heater (Peltier effect) and a temperature probe (Seebeck effect) to determine the volumetric heat capacity of the soil and hence water content ( θv). This is the first time that the DPHP method is implemented in a microdevice and the first integrated sensor for soil moisture. This microdevice is more suited to measure at different soil depths in a non-destructive and automated manner.Agricultural and Agro-industrial Science and Technology Institute of the University of Trás-os-Montes and Alto Douro