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Duarte C.M.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | Duarte C.M.,The Interdisciplinary Center | Fernandes A.C.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | Cardoso F.A.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | And 5 more authors.
IEEE Transactions on Magnetics | Year: 2015

Identification of bovine mastitis pathogens is necessary to control the disease, reduce the risk of chronic infections, and target the antimicrobial therapy to be prescribed. Development prospects for new bovine mastitis diagnosis methodologies go also through rapid and efficient devices that can offer a 'cow-side' use, meaning that raw milk collected for analysis should have limited pretreatment. This paper aims at developing a magnetic counter that identifies the presence of Streptococcus agalactiae (a Group B Streptococci) in raw milk. The detection is done with an integrated microfluidic platform, where 50 nm magnetic beads attached to Streptococcus agalactiae are dynamically detected by magnetoresistive sensors. This device allows the analysis of raw milk without bridging the microfluidic channels, making this integrated platform very attractive for fast bacteriological contamination screening. © 1965-2012 IEEE. Source

Fonseca L.P.,University of Lisbon | Martins V.C.B.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | Freitas P.P.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias
1st Portuguese Meeting in Biomedical Engineering, ENBENG 2011 | Year: 2011

It is thought that worldwide more than 109 analyses are now performed every day with a double-digit growth rate. Microreactors and analytical microdevices and biosensors can provide important role on the control of environment, bioprocesses, processed food, biomedical analysis, among others due to rapid analysis and high sensitivity. This work envisages showing the potential of microreactors and biosensors on two mainly applications: i) The development of enzyme-base analytical microreactors for detection of multi-analyte compounds (e.g. sugars, alcohols, aminoacids, organic acids, among others) based on enzyme immobilization carried out on CPG beads integrated in FIA/SIA systems and sol-gel matrix integrated in glass capillary and microchannels. ii) The manipulation of individual microbial cells and single strand DNA molecules with functional paramagnetic nano-and micro-beads and their detection with magneto-resistive sensors demonstrates the applicability of these biosensors for the detection of pathogen microorganisms (e.g. Salmonella) through two different strategies: hybridization of DNA molecules (DNA-chips) and antibody-antigen biorecognition (immuno-chips). © 2011 IEEE. Source

De Marcellis A.,University of LAquila | Cubells-Beltran M.-D.,University of Valencia | Reig C.,University of Valencia | Madrenas J.,Polytechnic University of Catalonia | And 4 more authors.
IET Circuits, Devices and Systems | Year: 2014

In this study, the authors report on two different electronic interfaces for low-power integrated circuits electric current monitoring through current-to-frequency (I-f) conversion schemes. This proposal displays the intrinsic advantages of the quasidigital systems regarding direct interfacing and self-calibrating capabilities. In addition, as current-sensing devices, they have made use of the giant magnetoresistance (GMR) technology because of its high sensitivity and compatibility with standard complementary metal oxide semiconductor processes. Single elements and Wheatstone bridges based on spin-valves and magnetic tunnel junctions have been considered. In this sense, schematic-level simulations for integration in Austria Microsystems 0.35 μm technology have been corroborated by means of experimental measurements with the help of printed circuit board prototypes and real GMR devices. Tables with relevant parameters (silicon area, power consumption, sensitivity etc.) have been constructed as practical tools for designers. Electric currents down to 2 μA have been resolved in this way. © The Institution of Engineering and Technology 2014. Source

Roldan A.,University of Granada | Reig C.,University of Valencia | Cubells-Beltran M.D.,University of Valencia | Roldan J.B.,University of Granada | And 3 more authors.
Solid-State Electronics | Year: 2010

An analytical compact model for giant magnetoresistance (GMR) based current sensors has been developed. Different spin-valve based full Wheatstone bridge sensors, with the current straps integrated in the chip, have been considered. These devices have been experimentally characterized in order to extract the model parameters. In this respect, we have focused on the sensors linear operation regime. The model, which allows the individual description of the magnetoresistive elements, has been implemented in a circuit simulator by means of a behavioral description language: Verilog-A. We also propose the use of the devices in a direct power measurement application at the integrated circuit (IC) level, by taking advantage of their multiplicative properties. A simple circuit is suggested, and analyzed in depth by means of the tested model, showing promising results regarding the application range. © 2010 Elsevier Ltd. All rights reserved. Source

Chicharo A.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | Cardoso F.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | Cardoso S.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | Freitas P.J.P.,Institute Engineering Of Sistemas E Computadores Microsistemas E Nanotecnologias | Freitas P.J.P.,International Iberian Nanotechnology Laboratory
IEEE Transactions on Magnetics | Year: 2015

This paper investigates real-time monitoring and detection of 10.5 nm magnetic nanoparticles (MNPs) (Fe3O4) flowing in a nitrocellulose (NC) membrane over two spin valve sensors. The fabricated device gives information on the concentration of MNP flowing through the NC membrane of a typical lateral flow test, and gives relevant dynamic characteristics, such as flow rate and MNP distribution on capillary-driven systems. Sensor output varies linearly with MNP concentration. Experiments show average flow rates varying from 0.2 to 0.3 mm/s depending on MNP concentration. Signal shape [V(t)] gives information on MNP spatial distribution at the particle front flowing over the sensor. © 2015 IEEE. Source

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