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The Scanning TMR Microscope for Biosensor Applications.

Vyas KN, Love DM, Ionescu A, Llandro J, Kollu P, Mitrelias T, Holmes S, Barnes CH - Biosensors (Basel) (2015)

Bottom Line: By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe.By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance.The quantitative nature of the instrument and its ability to produce vector maps of magnetic stray fields has the potential to provide significant advantages over other commonly used scanning magnetometry techniques.

View Article: PubMed Central - PubMed

Affiliation: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. kunalnvyas@gmail.com.

ABSTRACT
We present a novel tunnel magnetoresistance (TMR) scanning microscope set-up capable of quantitatively imaging the magnetic stray field patterns of micron-sized elements in 3D. By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe. By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance. The modular design, incorporating a TMR sensor with an optical microscope, renders this set-up a versatile platform for studying and imaging immobilised magnetic carriers and barcodes currently employed in biosensor platforms, magnetotactic bacteria and other complex magnetic domain structures of micron-sized entities. The quantitative nature of the instrument and its ability to produce vector maps of magnetic stray fields has the potential to provide significant advantages over other commonly used scanning magnetometry techniques.

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The data obtained when scanning a TMR sensor at varying heights below a three-bit tag and thereby measuring the stray field in a 50 × 150 × 10 µm3 volume. The sensitive axis is vertical, as seen in the figure, and the images are obtained from the real component of the signal. The z label of each image represents the distance from the sample in µm. Frequency: 833 Hz, time-constant: 50 ms, scan speed: 40 µm/s.
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biosensors-05-00172-f008: The data obtained when scanning a TMR sensor at varying heights below a three-bit tag and thereby measuring the stray field in a 50 × 150 × 10 µm3 volume. The sensitive axis is vertical, as seen in the figure, and the images are obtained from the real component of the signal. The z label of each image represents the distance from the sample in µm. Frequency: 833 Hz, time-constant: 50 ms, scan speed: 40 µm/s.

Mentions: Furthermore, our instrument can also conduct three-dimensional scans by varying the separation, z, between the sensor and the sample plane. Figure 8 presents the data obtained from imaging a three-bit tag from a distance of 12 to 2 µm. Despite the domain breakdown, we can see that our instrument is capable of discerning a signal from the elements, even when scanning from 12 µm away. However, this signal is just above the noise, and whilst it is possible to see the pattern in an image, we would not have much confidence of picking this signal out using a single-pass measurement, such as those presented in the one-dimensional scans.


The Scanning TMR Microscope for Biosensor Applications.

Vyas KN, Love DM, Ionescu A, Llandro J, Kollu P, Mitrelias T, Holmes S, Barnes CH - Biosensors (Basel) (2015)

The data obtained when scanning a TMR sensor at varying heights below a three-bit tag and thereby measuring the stray field in a 50 × 150 × 10 µm3 volume. The sensitive axis is vertical, as seen in the figure, and the images are obtained from the real component of the signal. The z label of each image represents the distance from the sample in µm. Frequency: 833 Hz, time-constant: 50 ms, scan speed: 40 µm/s.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493544&req=5

biosensors-05-00172-f008: The data obtained when scanning a TMR sensor at varying heights below a three-bit tag and thereby measuring the stray field in a 50 × 150 × 10 µm3 volume. The sensitive axis is vertical, as seen in the figure, and the images are obtained from the real component of the signal. The z label of each image represents the distance from the sample in µm. Frequency: 833 Hz, time-constant: 50 ms, scan speed: 40 µm/s.
Mentions: Furthermore, our instrument can also conduct three-dimensional scans by varying the separation, z, between the sensor and the sample plane. Figure 8 presents the data obtained from imaging a three-bit tag from a distance of 12 to 2 µm. Despite the domain breakdown, we can see that our instrument is capable of discerning a signal from the elements, even when scanning from 12 µm away. However, this signal is just above the noise, and whilst it is possible to see the pattern in an image, we would not have much confidence of picking this signal out using a single-pass measurement, such as those presented in the one-dimensional scans.

Bottom Line: By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe.By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance.The quantitative nature of the instrument and its ability to produce vector maps of magnetic stray fields has the potential to provide significant advantages over other commonly used scanning magnetometry techniques.

View Article: PubMed Central - PubMed

Affiliation: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, CB3-0HE Cambridge, UK. kunalnvyas@gmail.com.

ABSTRACT
We present a novel tunnel magnetoresistance (TMR) scanning microscope set-up capable of quantitatively imaging the magnetic stray field patterns of micron-sized elements in 3D. By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe. By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterize the complex domain structures by displaying the real component, the amplitude and the phase of the sensor's impedance. The modular design, incorporating a TMR sensor with an optical microscope, renders this set-up a versatile platform for studying and imaging immobilised magnetic carriers and barcodes currently employed in biosensor platforms, magnetotactic bacteria and other complex magnetic domain structures of micron-sized entities. The quantitative nature of the instrument and its ability to produce vector maps of magnetic stray fields has the potential to provide significant advantages over other commonly used scanning magnetometry techniques.

Show MeSH