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Open AccessArticle

The Scanning TMR Microscope for Biosensor Applications

Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK
Cambridge Biomagnetics Ltd., St John's Innovation Centre, Cowley Road, CB4-0WS Cambridge, UK
Toshiba Research Europe Ltd., Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, CB4-OGZ Cambridge, UK
Authors to whom correspondence should be addressed.
Academic Editor: Richard Luxton
Biosensors 2015, 5(2), 172-186;
Received: 23 December 2014 / Revised: 13 March 2015 / Accepted: 27 March 2015 / Published: 2 April 2015
(This article belongs to the Special Issue Magnetic Biosensors)
We present a novel tunnel magnetoresistance (TMR) scanning microscopeset-up capable of quantitatively imaging the magnetic stray field patterns of micron-sizedelements in 3D. By incorporating an Anderson loop measurement circuit for impedancematching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe. By 3Drastering a mounted TMR sensor over our magnetic barcodes, we are able to characterisethe complex domain structures by displaying the real component, the amplitude and thephase of the sensor’s impedance. The modular design, incorporating a TMR sensor withan optical microscope, renders this set-up a versatile platform for studying and imagingimmobilised magnetic carriers and barcodes currently employed in biosensor platforms,magnetotactic bacteria and other complex magnetic domain structures of micron-sizedentities. The quantitative nature of the instrument and its ability to produce vector maps ofmagnetic stray fields has the potential to provide significant advantages over other commonlyused scanning magnetometry techniques. View Full-Text
Keywords: magnetic carriers; TMR-scanning microscope; 3D magnetic stray field mapping;domain wall characterisation magnetic carriers; TMR-scanning microscope; 3D magnetic stray field mapping;domain wall characterisation
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Vyas, K.N.; Love, D.M.; Ionescu, A.; Llandro, J.; Kollu, P.; Mitrelias, T.; Holmes, S.; Barnes, C.H.W. The Scanning TMR Microscope for Biosensor Applications. Biosensors 2015, 5, 172-186.

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