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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.


(a) The normalized y-component of the total magnetic field from a single magnetic bead for an infinitely long sensor of width w as function of the position of the bead. The bead is magnetized along the y-direction with magnetic moment my and is positioned at (yp, zp) with respect to the sensor centroid. (b) The mean field  acting on a single sensor stripe as a function of the normalized width wBAA of the biologically active area. The calculation was done for t/w = 0.1 and the indicated values of zSeBL and zSpBL.
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f2: (a) The normalized y-component of the total magnetic field from a single magnetic bead for an infinitely long sensor of width w as function of the position of the bead. The bead is magnetized along the y-direction with magnetic moment my and is positioned at (yp, zp) with respect to the sensor centroid. (b) The mean field acting on a single sensor stripe as a function of the normalized width wBAA of the biologically active area. The calculation was done for t/w = 0.1 and the indicated values of zSeBL and zSpBL.

Mentions: The MR sensor detects the presence of magnetic beads via their perturbation of the externally applied magnetic field. However, both the magnitude and sign of the signal due to a single magnetic bead depend on the position of the bead relative to the sensor stripe. This is illustrated in Fig. 2a, where the signal from a single bead is plotted as function of its position. As can be seen in Fig. 2a, the bead may provide a positive or negative field depending on whether it is positioned on top of or outside the sensor stripe. Moreover, beads with lower values of provide a stronger field.


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

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

(a) The normalized y-component of the total magnetic field from a single magnetic bead for an infinitely long sensor of width w as function of the position of the bead. The bead is magnetized along the y-direction with magnetic moment my and is positioned at (yp, zp) with respect to the sensor centroid. (b) The mean field  acting on a single sensor stripe as a function of the normalized width wBAA of the biologically active area. The calculation was done for t/w = 0.1 and the indicated values of zSeBL and zSpBL.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: (a) The normalized y-component of the total magnetic field from a single magnetic bead for an infinitely long sensor of width w as function of the position of the bead. The bead is magnetized along the y-direction with magnetic moment my and is positioned at (yp, zp) with respect to the sensor centroid. (b) The mean field acting on a single sensor stripe as a function of the normalized width wBAA of the biologically active area. The calculation was done for t/w = 0.1 and the indicated values of zSeBL and zSpBL.
Mentions: The MR sensor detects the presence of magnetic beads via their perturbation of the externally applied magnetic field. However, both the magnitude and sign of the signal due to a single magnetic bead depend on the position of the bead relative to the sensor stripe. This is illustrated in Fig. 2a, where the signal from a single bead is plotted as function of its position. As can be seen in Fig. 2a, the bead may provide a positive or negative field depending on whether it is positioned on top of or outside the sensor stripe. Moreover, beads with lower values of provide a stronger field.

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.