Detektion superparamagnetischer Marker mittels GMI-Sensorik (Detection of superparamagnetic markers with GMI-Sensors)

Abstract

Der Riesen-Magnetoimpedanz-Effekt (GMI) beschreibt die starke Abhängigkeit der Impedanz weichmagnetischer Mikrodrähte oder dünner Schichtsysteme von der Größe eines angelegten, relativ kleinen externen Feldes. Die Impedanzänderung kann bei mehreren hundert Prozent liegen. Fast alle erdenklichen Anwendungen sind vorgeschlagen worden, einige werden bereits angewandt, z.B. das Messen von extrem kleinen Feldern. Zu Montage- und Integrationszwecken eignen sich Dünnschicht-Systeme besser als Drähte. Daher haben wir uns auf die Entwicklung und Charakterisierung von dünnen Filmen konzentriert. Die Sensoren bestehen aus gesputterten FeCuNbSiB/Cu/FeCuNbSiB-Trilagensystemen. Bei diesen Strukturen erhält man im Gegensatz zu GMI-Drähten eine ausgeprägte Richtungsanisotropie bezüglich des angelegten externen Magnetfeldes. Wir diskutieren die verschiedenen Möglichkeiten der GMI-Messung und des Sensoraufbaus und zeigen, dass mit diesem Sensor kleine Mengen superparamagnetischer Partikel detektiert werden können.

Microwire array for giant magneto-impedance detection of magnetic particles for biosensor prototype

“…In the research field of the magnetic bio-detection, following the giant magneto-resistance (GMR) biosensor emergence [2], new biosensor prototypes, based on giant magneto-impedance (GMI) effect, were studied [3,4]. The GMI effect consists in an abrupt variation of the impedance of a soft magnetic conductor passed by a high-frequency current when subjected to a small direct current (DC) magnetic field [5].…”

“…Based on GMI effect, single amorphous ribbon was used as sensing element into a biosensor prototype for the commercial Dynabeads detection [6]. Also, GMI prototypes based on thin film trilayer systems were tested [4].…”

Giant magnetoimpedance for biosensing: Advantages and shortcomings

“…The presence of the immersed in ethanol Evotec s beads was detected in a high field of about 100 Oe but the reported sensitivity was rather small (of about 0.07%) [10]. be caused by the contribution of non-magnetic origin, namely the presence of the phase shifts due to the electrical lengths of the circuit [19].…”

“…MI magnetic field sensors adapted for the detection of magnetic markers are still under development: all prototypes which have been reported until now, instead of employing of a suitable biochemistry to count the selectively attached markers, deal with free beads immersed in a buffer [9][10][11][12][13] or spread on the surface of the MI sensitive element ''in dry'' [14]. These prototypes were based on rapidly quenched amorphous ribbons [9,11,13], rapidly quenched wire [14], glass covered microwires [12,14] or MI multilayers [10]. Ribbon-based MI elements, which are inexpensive, very sensitive to external field detectors work in relatively low-frequency range well adapted to standard electronic circuitry solutions of 1-10 MHz.…”

High Performance Magnetoimpedance in FeNi/Ti Nanostructured Multilayers with Opened Magnetic Flux

“…2 There are limited studies related to MI biosensor prototypes based on multilayered film sensitive elements, [8][9][10] which indicate the necessity to improve the biosensor design. Two problems can be mentioned as the most important: a necessity to improve the low field detector sensitivity and the difficulties of installing a thin film sensitive element deposited onto a rigid substrate into microfluidic system, without significantly decreasing the sensitivity of the magnetic detector.…”