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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.


Calculations of normalized magnetic field  from an infinite SpBL array.(a) Color map of . The sensor stripes placed at  are indicated by the black bars. Red and blue colors indicate positive and negative field values, respectively. (b) Values of  at  vs.  for the indicated values of . (c) Average normalized magnetic field  vs.  for the indicated values of . The inset shows  on a linear scale vs.  for SpBL (solid line) and SeBL (dashed line) arrays, respectively, for a geometry with . All calculations were done with .
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f4: Calculations of normalized magnetic field from an infinite SpBL array.(a) Color map of . The sensor stripes placed at are indicated by the black bars. Red and blue colors indicate positive and negative field values, respectively. (b) Values of at vs. for the indicated values of . (c) Average normalized magnetic field vs. for the indicated values of . The inset shows on a linear scale vs. for SpBL (solid line) and SeBL (dashed line) arrays, respectively, for a geometry with . All calculations were done with .

Mentions: We consider an infinite array of sensor stripes and first discuss general properties of the magnetic field. Figure 4a shows an example of calculated for an array of SpBL with no SeBL. The field is strongest near the poles (faces) of the bead layer and it displays a high degree of symmetry. An SpBL/SeBL array provides a positive/negative in the sensor stripe, respectively. When considering the field from any layer, the shape of across the sensor depends on the heights of the bead layers as illustrated in Fig. 4b. For low -values the SpBL gives rise to a strong field at the edge of the sensor. However, when increases and becomes larger than and comparable to , the fields from different poles will overlap. This results in a reduction of the overall field strength, but the resulting will be more uniform and assumes its maximum value over the middle of the sensor stripe.


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

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

Calculations of normalized magnetic field  from an infinite SpBL array.(a) Color map of . The sensor stripes placed at  are indicated by the black bars. Red and blue colors indicate positive and negative field values, respectively. (b) Values of  at  vs.  for the indicated values of . (c) Average normalized magnetic field  vs.  for the indicated values of . The inset shows  on a linear scale vs.  for SpBL (solid line) and SeBL (dashed line) arrays, respectively, for a geometry with . All calculations were done with .
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Calculations of normalized magnetic field from an infinite SpBL array.(a) Color map of . The sensor stripes placed at are indicated by the black bars. Red and blue colors indicate positive and negative field values, respectively. (b) Values of at vs. for the indicated values of . (c) Average normalized magnetic field vs. for the indicated values of . The inset shows on a linear scale vs. for SpBL (solid line) and SeBL (dashed line) arrays, respectively, for a geometry with . All calculations were done with .
Mentions: We consider an infinite array of sensor stripes and first discuss general properties of the magnetic field. Figure 4a shows an example of calculated for an array of SpBL with no SeBL. The field is strongest near the poles (faces) of the bead layer and it displays a high degree of symmetry. An SpBL/SeBL array provides a positive/negative in the sensor stripe, respectively. When considering the field from any layer, the shape of across the sensor depends on the heights of the bead layers as illustrated in Fig. 4b. For low -values the SpBL gives rise to a strong field at the edge of the sensor. However, when increases and becomes larger than and comparable to , the fields from different poles will overlap. This results in a reduction of the overall field strength, but the resulting will be more uniform and assumes its maximum value over the middle of the sensor stripe.

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.