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De Almeida T.M.,Institute Engineering Of Sistemas E Computadores Randd Inesc Id | De Almeida T.M.,University of Lisbon | Piedade M.S.,Institute Engineering Of Sistemas E Computadores Randd Inesc Id | Piedade M.S.,University of Lisbon | And 7 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2010

A fully integrated biochip based on a 16 X 16 scalable matrix structure of aluminum oxide magnetic tunnel junctions (MTJs) and thin-film diodes (TFDs of hydrogenated amorphous silicon) was fabricated and included as the biosensor of a portable handheld microsystem developed for biomolecular recognition detection using magnetic labels [deoxyribonucleic acid (DNA) hybridization, antibody antigen interaction, etc.]. The system uses magnetic field arraying of magnetically tagged biomolecules and can potentially be used to detect single or few biomolecules. Each biosensor matrix node is the series between a TFD (p-i-n or Schottky-barrier type) and an MTJ. In this paper, this matrix basic cell biosensor element is completely characterized and modeled. Experimental measured data are provided and compared with the proposed theoretical models results. It is shown that the diode may be used both as the matrix switching device and as an in-site temperature sensor and that the MTJ may act as the magnetoresistive sensor for detecting the fringe field of immobilized magnetic markers. Therefore, the fabricated fully integrated biochip included in the developed handheld microsystem may be used for biomolecular recognition. © 2009 IEEE.

Lopes P.A.C.,University of Lisbon | Germano J.,University of Lisbon | De Almeida T.M.,University of Lisbon | Sousa L.A.,University of Lisbon | And 5 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2010

This paper proposes techniques for the extraction of biological information in a recently developed handheld biochip-based microsystem. The microsystem is based on a magnetoresistive array biochip composed of a number of sensing sites with magnetic tunneling junctions (MTJ) and diodes. Different techniques are addressed to drive the MTJs with different types of signals. Different filtering strategies that allow the recovery of biological signals from the noise without overly increasing either the time required for accessing the sensors or the power consumption of the board are proposed. Finally, new techniques and algorithms are proposed to deal with the variability of the fabrication parameters of the MTJ and the diodes. Experiments with the system in a setup to detect actual biological signals are presented with encouraging results. © 2008 IEEE.

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