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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: 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.

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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Related in: MedlinePlus

The figure illustrates how the instrument mechanics operate. The sample and sensor can be translated in all directions with respect to each other using three micro-stages that operate in orthogonal directions; x, y and z. The micro-stages, to which the sensor and sample are attached, are fixed to the microscope stage in order to enable the focussing of the objective. This allows either the sample or the sensor to be brought into the focal plain. When the vertical separation between them is small enough, as it is during measurements, both can be viewed at the same time.
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biosensors-05-00172-f003: The figure illustrates how the instrument mechanics operate. The sample and sensor can be translated in all directions with respect to each other using three micro-stages that operate in orthogonal directions; x, y and z. The micro-stages, to which the sensor and sample are attached, are fixed to the microscope stage in order to enable the focussing of the objective. This allows either the sample or the sensor to be brought into the focal plain. When the vertical separation between them is small enough, as it is during measurements, both can be viewed at the same time.

Mentions: The mechanics and optics of the instrument consist of a Leica DMLM microscope, three T25-D/M micro-stages from Elliot Scientific (now supported by Thorlabs), three TDC001 T-Cube DC servo motor drivers (Thorlabs), a CCD sensor and a custom-built sensor head holder and are best understood graphically by viewing Figure 3. The sample is placed/fabricated on a transparent substrate and is mounted upside down. It is attached to the x- and y-stages and can therefore be moved around in-plane. The sensor head is attached to a z-stage, which allows the sensor to approach the sample from below. This whole contraption sits inside a microscope, allowing us to view the sample and the sensor through the transparent sample substrate. The micro-stages control the relative x, y and z positions of the sensor and sample, whilst the microscope stage can be used to bring different planes into focus. The CCD-sensor is attached to the microscope to negate the need to constantly look through the eyepieces. The micro-stages are controlled by the laptop via their individual drivers (T-Cube) supplied by Thorlabs.


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 figure illustrates how the instrument mechanics operate. The sample and sensor can be translated in all directions with respect to each other using three micro-stages that operate in orthogonal directions; x, y and z. The micro-stages, to which the sensor and sample are attached, are fixed to the microscope stage in order to enable the focussing of the objective. This allows either the sample or the sensor to be brought into the focal plain. When the vertical separation between them is small enough, as it is during measurements, both can be viewed at the same time.
© Copyright Policy
Related In: Results  -  Collection

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

biosensors-05-00172-f003: The figure illustrates how the instrument mechanics operate. The sample and sensor can be translated in all directions with respect to each other using three micro-stages that operate in orthogonal directions; x, y and z. The micro-stages, to which the sensor and sample are attached, are fixed to the microscope stage in order to enable the focussing of the objective. This allows either the sample or the sensor to be brought into the focal plain. When the vertical separation between them is small enough, as it is during measurements, both can be viewed at the same time.
Mentions: The mechanics and optics of the instrument consist of a Leica DMLM microscope, three T25-D/M micro-stages from Elliot Scientific (now supported by Thorlabs), three TDC001 T-Cube DC servo motor drivers (Thorlabs), a CCD sensor and a custom-built sensor head holder and are best understood graphically by viewing Figure 3. The sample is placed/fabricated on a transparent substrate and is mounted upside down. It is attached to the x- and y-stages and can therefore be moved around in-plane. The sensor head is attached to a z-stage, which allows the sensor to approach the sample from below. This whole contraption sits inside a microscope, allowing us to view the sample and the sensor through the transparent sample substrate. The micro-stages control the relative x, y and z positions of the sensor and sample, whilst the microscope stage can be used to bring different planes into focus. The CCD-sensor is attached to the microscope to negate the need to constantly look through the eyepieces. The micro-stages are controlled by the laptop via their individual drivers (T-Cube) supplied by Thorlabs.

Bottom Line: 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.

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
Related in: MedlinePlus