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Sensors 2015, 15(6), 12526-12538; doi:10.3390/s150612526

Strong Ferromagnetically-Coupled Spin Valve Sensor Devices for Droplet Magnetofluidics

1
Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
2
Material Systems for Nanoelectronics, Chemnitz University of Technology, Reichenhainerstr. 70, 09107 Chemnitz, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Andreas Hütten
Received: 13 April 2015 / Accepted: 22 May 2015 / Published: 27 May 2015
(This article belongs to the Special Issue Magnetic Sensor Device-Part 1)
View Full-Text   |   Download PDF [654 KB, uploaded 28 May 2015]   |  

Abstract

We report a magnetofluidic device with integrated strong ferromagnetically-coupled and hysteresis-free spin valve sensors for dynamic monitoring of ferrofluid droplets in microfluidics. The strong ferromagnetic coupling between the free layer and the pinned layer of spin valve sensors is achieved by reducing the spacer thickness, while the hysteresis of the free layer is eliminated by the interplay between shape anisotropy and the strength of coupling. The increased ferromagnetic coupling field up to the remarkable 70 Oe, which is five-times larger than conventional solutions, brings key advantages for dynamic sensing, e.g., a larger biasing field giving rise to larger detection signals, facilitating the operation of devices without saturation of the sensors. Studies on the fundamental effects of an external magnetic field on the evolution of the shape of droplets, as enabled by the non-visual monitoring capability of the device, provides crucial information for future development of a magnetofluidic device for multiplexed assays. View Full-Text
Keywords: droplet microfluidics; spin valve; ferromagnetic coupling; high field sensing; ferrofluid droplet microfluidics; spin valve; ferromagnetic coupling; high field sensing; ferrofluid
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Lin, G.; Makarov, D.; Schmidt, O.G. Strong Ferromagnetically-Coupled Spin Valve Sensor Devices for Droplet Magnetofluidics. Sensors 2015, 15, 12526-12538.

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