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On the importance of sensor height variation for detection of magnetic labels by magnetoresistive sensors.

Henriksen AD, Wang SX, Hansen MF - Sci Rep (2015)

Bottom Line: We systematically analyze the signal from both a single sensor stripe and an array of sensor stripes as function of the geometrical parameters of the sensor stripes as well as the distribution of magnetic labels over the stripes.We therefore propose a shift of paradigm to maximize the signal due to magnetic labels between sensor stripes.Guidelines for this optimization are provided and illustrated for an experimental case from the literature.

View Article: PubMed Central - PubMed

Affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kongens Lyngby, Denmark.

ABSTRACT
Magnetoresistive sensors are widely used for biosensing by detecting the signal from magnetic labels bound to a functionalized area that usually covers the entire sensor structure. Magnetic labels magnetized by a homogeneous applied magnetic field weaken and strengthen the applied field when they are over and outside the sensor area, respectively, and the detailed origin of the sensor signal in experimental studies has not been clarified. We systematically analyze the signal from both a single sensor stripe and an array of sensor stripes as function of the geometrical parameters of the sensor stripes as well as the distribution of magnetic labels over the stripes. We show that the signal from sensor stripes with a uniform protective coating, contrary to conventional wisdom in the field, is usually dominated by the contribution from magnetic labels between the sensor stripes rather than by the labels on top of the sensor stripes because these are at a lower height. We therefore propose a shift of paradigm to maximize the signal due to magnetic labels between sensor stripes. Guidelines for this optimization are provided and illustrated for an experimental case from the literature.

No MeSH data available.


Illustration of cross-section in the yz-plane of (a) the single sensor stripe geometry, and (b) the periodic sensor stripe array geometry with definition of geometrical parameters and the coordinate system.
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f1: Illustration of cross-section in the yz-plane of (a) the single sensor stripe geometry, and (b) the periodic sensor stripe array geometry with definition of geometrical parameters and the coordinate system.

Mentions: Magnetoresistive (MR) sensors show great promise as the emerging technology for magnetic biodetection. These sensors usually consist of a magnetic stack in a stripe geometry with a resistance that depends linearly on the experienced field. We will assume that the sensor geometry is either a single stripe17 or an array of stripes6 aligned along the x-direction. Often, the stripe length is much larger than the stripe width and we will therefore assume that the stripes are infinitely long such that the problem is reduced to two dimensions in the yz-plane (Fig. 1). Moreover, we will assume that the sensor detects the average value of the y-component Hy of the total magnetic field experienced by the sensor. Usually, the presence of magnetic beads attached to the biologically active area (BAA) is detected by comparing the average magnetic field detected by the sample sensor with that detected by a reference sensor such that the resulting sensor signal S can be written as


On the importance of sensor height variation for detection of magnetic labels by magnetoresistive sensors.

Henriksen AD, Wang SX, Hansen MF - Sci Rep (2015)

Illustration of cross-section in the yz-plane of (a) the single sensor stripe geometry, and (b) the periodic sensor stripe array geometry with definition of geometrical parameters and the coordinate system.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508666&req=5

f1: Illustration of cross-section in the yz-plane of (a) the single sensor stripe geometry, and (b) the periodic sensor stripe array geometry with definition of geometrical parameters and the coordinate system.
Mentions: Magnetoresistive (MR) sensors show great promise as the emerging technology for magnetic biodetection. These sensors usually consist of a magnetic stack in a stripe geometry with a resistance that depends linearly on the experienced field. We will assume that the sensor geometry is either a single stripe17 or an array of stripes6 aligned along the x-direction. Often, the stripe length is much larger than the stripe width and we will therefore assume that the stripes are infinitely long such that the problem is reduced to two dimensions in the yz-plane (Fig. 1). Moreover, we will assume that the sensor detects the average value of the y-component Hy of the total magnetic field experienced by the sensor. Usually, the presence of magnetic beads attached to the biologically active area (BAA) is detected by comparing the average magnetic field detected by the sample sensor with that detected by a reference sensor such that the resulting sensor signal S can be written as

Bottom Line: We systematically analyze the signal from both a single sensor stripe and an array of sensor stripes as function of the geometrical parameters of the sensor stripes as well as the distribution of magnetic labels over the stripes.We therefore propose a shift of paradigm to maximize the signal due to magnetic labels between sensor stripes.Guidelines for this optimization are provided and illustrated for an experimental case from the literature.

View Article: PubMed Central - PubMed

Affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kongens Lyngby, Denmark.

ABSTRACT
Magnetoresistive sensors are widely used for biosensing by detecting the signal from magnetic labels bound to a functionalized area that usually covers the entire sensor structure. Magnetic labels magnetized by a homogeneous applied magnetic field weaken and strengthen the applied field when they are over and outside the sensor area, respectively, and the detailed origin of the sensor signal in experimental studies has not been clarified. We systematically analyze the signal from both a single sensor stripe and an array of sensor stripes as function of the geometrical parameters of the sensor stripes as well as the distribution of magnetic labels over the stripes. We show that the signal from sensor stripes with a uniform protective coating, contrary to conventional wisdom in the field, is usually dominated by the contribution from magnetic labels between the sensor stripes rather than by the labels on top of the sensor stripes because these are at a lower height. We therefore propose a shift of paradigm to maximize the signal due to magnetic labels between sensor stripes. Guidelines for this optimization are provided and illustrated for an experimental case from the literature.

No MeSH data available.