Magnetoresistive sensor for real-time single nucleotide polymorphism genotyping

Rizzi, Giovanni; Østerberg, Frederik Westergaard; Dufva, Martin; Hansen, Mikkel Fougt

doi:10.1016/j.bios.2013.09.026

Cited by 35 publications

(61 citation statements)

References 22 publications

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“…The magnetized beads generate a dipole magnetic field that allows their detection with no need for other external magnetic fields. The magnetic field from the beads (B b ) is proportional to the sensor bias current 7,15,18,19 and can be written as…”

Section: Sensor Response To Beads Magnetized By Sensor Self-fieldmentioning

confidence: 99%

“…where c is a proportionality factor depending on the bead properties and their distribution (compared to our previous work, 7,15 to keep the notation simple, we here include a factor of l 0 in c and the current is the total sensor current I x ). Combining Eqs.…”

Section: Sensor Response To Beads Magnetized By Sensor Self-fieldmentioning

confidence: 99%

“…Moreover, the signal was about 90% higher than that obtained for the stack with t FM ¼ 20 nm and t Cu ¼ 0 nm used in our previous studies. 7,14 Operation of a given sensor geometry at fixed power ensures that the maximum signal is obtained with a controlled influence of the sensor self-heating. As mentioned above, the sensor length can be tailored to additionally respect constraints on the applied voltage with minimal influence onS 0 as long as the sensor length l is much larger than the sensor width w. A change of w will affect both B sh and c in a non-trivial manner.…”

Section: B Consequences For Magnetic Bead Detectionmentioning

confidence: 99%

“…1,2 In these, magnetic beads are usually used as specific labels that bind to the target analyte, and because the biological sample provides no magnetic background signal, the analyte may be detected in real-time with high sensitivity and specificity. [3][4][5][6][7][8] Magnetoresistive biosensors based on the planar Hall effect, 9-11 magnetic tunneling effect, 12,13 or giant magnetoresistance effect [4][5][6] have been proposed for this application. We have previously demonstrated the use of planar Hall effect bridge (PHEB) magnetic field sensors in both volumeand surface-based detection schemes, 7,14,15 and how the sensor design can be optimized towards such diverse applications.…”

Section: Introductionmentioning

confidence: 99%

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Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

Henriksen

Rizzi

Hansen

2016

Journal of Applied Physics

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Articles you may be interested inThe stack composition in trilayer Planar Hall effect bridge sensors is investigated experimentally to identify the optimal stack for magnetic bead detection using the sensor self-field. The sensors were fabricated using exchange-biased stacks Ni 80 Fe 20 (t FM )/Cu(t Cu )/Mn 80 Ir 20 (10 nm) with t FM ¼ 10, 20, and 30 nm, and 0 t Cu 0.6 nm. The sensors were characterized by magnetic hysteresis measurements, by measurements of the sensor response vs. applied field, and by measurements of the sensor response to a suspension of magnetic beads magnetized by the sensor self-field due to the sensor bias current. The exchange bias field was found to decay exponentially with t Cu and inversely with t FM . The reduced exchange field for larger values of t FM and t Cu resulted in higher sensitivities to both magnetic fields and magnetic beads. We argue that the maximum magnetic bead signal is limited by Joule heating of the sensors and, thus, that the magnetic stacks should be compared at constant power consumption. For a fixed sensor geometry, the figure of merit for this comparison is the magnetic field sensitivity normalized by the sensor bias voltage. In this regard, we found that sensors with t FM ¼ 20 nm or 30 nm outperformed those with t FM ¼ 10 nm by a factor of approximately two, because the latter have a reduced AMR ratio. Further, the optimum layer thicknesses, t Cu % 0.6 nm and t FM ¼ 20-30 nm, gave a 90% higher signal compared to the corresponding sensors with t Cu ¼ 0 nm. V C 2016 AIP Publishing LLC.

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Section: Sensor Response To Beads Magnetized By Sensor Self-fieldmentioning

confidence: 99%

Section: Sensor Response To Beads Magnetized By Sensor Self-fieldmentioning

confidence: 99%

Section: B Consequences For Magnetic Bead Detectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Planar Hall effect bridge sensors with NiFe/Cu/IrMn stack optimized for self-field magnetic bead detection

Henriksen

Rizzi

Hansen

2016

Journal of Applied Physics

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“…These give rise to a magnetic field of magnitude c 1 vI bar , where c 1 is a positive constant depending on the distribution and amount of magnetic beads as well as the sensor geometry, which relates the current times the magnetic bead susceptibility to the average magnetic field experienced by the sensor due to the magnetic beads. 20,21 In both cases, the direction of the self-field is given byĤ sf ¼ ÀÎ Âẑ, whereÎ andẑ are unit vectors along the current direction in the bar and the z-direction, respectively (cf. Fig.…”

Section: Theory a Sensor Construction Elementsmentioning

confidence: 99%

Planar Hall effect bridge geometries optimized for magnetic bead detection

Østerberg

Rizzi

Henriksen

et al. 2014

Journal of Applied Physics

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Articles you may be interested inNovel designs of planar Hall effect bridge sensors optimized for magnetic bead detection are presented and characterized. By constructing the sensor geometries appropriately, the sensors can be tailored to be sensitive to an external magnetic field, the magnetic field due to beads being magnetized by the sensor self-field or a combination thereof. The sensors can be made nominally insensitive to small external magnetic fields, while being maximally sensitive to magnetic beads, magnetized by the sensor self-field. Thus, the sensor designs can be tailored towards specific applications with minimal influence of external variables. Three different sensor designs are analyzed theoretically. To experimentally validate the theoretical signals, two sets of measurements are performed. First, the sensor signals are characterized as function of an externally applied magnetic field. Then, measurements of the dynamic magnetic response of suspensions of magnetic beads with a nominal diameter of 80 nm are performed. Furthermore, a method to amplify the signal by appropriate combinations of multiple sensor segments is demonstrated. V C 2014 AIP Publishing LLC.

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