Carlos Baleizão (Chemistry field) and Ana Maria Botelho do Rego (Nanomaterials field), both from CQFM-IST, were awarded with a Honourable Mention in the 2010 UTL/Santander Totta Scientific Awards. (Oct. 15 2010)
José Gaspar Martinho, Mário N. Berberan-Santos, José Paulo Farinha and Fábio Fernandes from CQFM; João Pedro Araújo, David Schmool and Hélder Crespo from IFIMUP; and Susana Freitas and Ricardo Ferreira from INESC-MN were awarded with research projects from Fundação para a Ciência e a Tecnologia/Portugal. (Sept. 1 2010)
Patterned functionalization layer for sub-µL DNA solid-phase immobilization and hybridization
Sensors and Actuators B 149 (2010) 432–438 |www|
The present work focuses on the patterning of a silane layer resulting from the reaction between a SiO2 surface and alkoxysilane (3-aminopropyl) triethoxysilane, APTES. The chemical composition and topography of the APTES layer are characterized using X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM), respectively. The effect of organic versus aqueous silanization media at different pH values, are compared. Micropatterning of the silanized layer is demonstrated and used to electrostatically immobilize single-stranded DNA probes, and to covalently immobilize thiolated single-stranded DNA probes after a cross-linking reaction with sulfo-EMCS. The hybridization efficiency of complementary DNA targets for both immobilization strategies is presented. The solid-phase DNA reactions were successfully demonstrated on surface squares of patterned functionalization layer, with dimensions in the micron scale, integrated on a surface microfluidic structure for sub-µL reaction volumes.
Wheatstone bridge sensor composed of linear MgO magnetic tunnel junctions
Journal of Applied Physics 107, 09E712 (2010)|www|
A full Wheatstone bridge sensor composed of linear MgO based magnetic tunnel junctions _MTJ_was designed and achieved. The magnetization direction of reference layers in the required bridge arms was successfully switched by using local current heating method, also demonstrating a viable method of manipulation of pinning direction for exchange bias system on a chip level. The final bridge output shows approximately full signal of individual MTJ but almost null output in the absence of any applied sensing field and small offset of voltage and field.
Tunneling processes in thin MgO magnetic junctions, J. M. Teixeira, J. Ventura, J. P. Araujo, J. B. Sousa, P. Wisniowski, and P. P. Freitas, Appl. Phys. Lett. 96, 262506 (2010)|www|
Magnetic tunnel junctions (MTJs) with MgO barriers are used in a variety of applications, from read heads to novel microwave devices. In this work, we probed the temperature (T) dependence of the electrical transport of sputtered CoFeB/MgO/CoFeB MTJs with different barrier thicknesses (tb = 0.75–1.35 nm). We show evidence that spin-polarized direct elastic tunneling is the dominant mechanism determining the T-dependence of the tunnel conductance (G) and magnetoresistance for tb ? 0.85?nm. Also, the electronic thermal smearing near the Fermi level plays a key role in G(T). We observe the onset of pinholes for MTJs with 0.75 nm of MgO, with a transition to metallic-like transport.