Sensors and Biosensors Related to Magnetic Nanoparticles

This book describes interesting examples of magnetic materials with magnetic nanoparticles or compact devices using composites with nanoparticles, including new engineering solutions and theoretical contributions on the magnetic biosensing of soft matter composites. Authors from different countries formed international team of experts sharing 10 contributed papers, 1 feature paper, and 1 topical review

Miniature Magnetic Sensors

Magnetic sensors are widely used in nearly all engineering and industrial sectors, including high-density magnetic recording, navigation, target detection, anti-theft systems, non-destructive testing, magnetic labeling, space research, and bio-magnetic measurements in the human body. Miniature magnetic sensors with high sensitivity are particularly advantageous in biomedical and specialized industrial applications. Amongst the various extant magnetic sensors, Micro-Electro-Mechanical System (MEMS) and Giant Magneto impedance (GMI) sensors have the ability to sense low levels of magnetic field in the order of 10 millitesla as well as the space to be further miniaturized. In this thesis, MEMS and GMI sensors are studied in detail both theoretically and experimentally. Multiphysics analyses have been developed to provide a path to further investigate these two types of sensors for various sensor configurations. Several prototype units are successfully developed, fabricated and tested to verify the validity of these models. MEMS reed sensors consist of tri-layer beams of Au/Ni/Au. The actuation of these sensors is initiated by the magnetic force to maintain the continuity of magnetic field streamlines. The Ni layer is deployed as the main magnetic core, and the gold layers are used to enhance the contact quality of the switches. In this work, a unique fabrication process is developed that significantly reduces the number of masking and lithography steps. As well, a detailed finite element method is presented to study the behavior of these sensors and to optimize the device performance. The FEM study considers various magnetic environments, providing a performance map for the sensors. Having a performance map is essential for a system's operation and for tracking its operational behavior. The study also considers the effects of various device formations and packaging for these types of sensors. The generated magnetic force is observed to be much higher than the required mechanical force for device actuation. The GMI sensors exhibit many advantages over their conventional counterparts. In particular, thermal stability and high sensitivity make GMI sensors attractive candidates for a wide range of applications. The GMI sensors are based on concepts different from those for conventional giant magneto resistance (GMR) sensors. GMI sensors have been under active research only in the past decade. In this thesis, thin film multilayer GMI sensors are realized using microfabrication technology. The fabricated sensors are tri-layers of Co73Si12B15 /Au./ Co73Si12B15 The thin film GMI sensors are studied in detail using FEM simulation, and several sensors are developed, fabricated and tested to work in the millitesla range. A post-processing step is proposed to optimize the performance of GMI sensors and to enhance their magnetic sensitivity. The post-processing characterization shows that annealing the devices with a specific annealing cycle has the optimal effect of enhancing the magnetic characteristics of CoSiB. The sensors are treated with this post-processing recipe, demonstrating a considerable increase in their magneto impedance (MI) ratio. The research has made a contribution to establishing the engineering foundation toward the development of low-cost miniature GMI magnetic sensors for low field intensity applications

Post-processing Routes for Design of Giant Magnetoimpedance Response and Domain Wall Dynamics Control in Glass-coated Magnetic Microwires

215 p.En esta tesis se presenta el estado actual del arte en la producción, propiedades y aplicaciones demicrohilos magnéticos recubiertos de vidrio junto con las técnicas experimentales empleadas para laproducción y caracterización de los materiales estudiados se tratan efectos novedosos en microhilosmagnéticamente blandos recubiertos de vidrio. El trabajo se enfoca en: i) microhilos amorfos ricos en Fecon tratamiento térmico optimizado para la mejora del efecto de magnetoimpedancia gigante (GMI) ydinámica de pared de dominio mejorada; ii) microhilos amorfos a base de Fe y Co con anisotropíamagnética graduada; y iii) Microhilos basados en Co con efecto conjunto de alto GMI y rápidapropagación de pared de dominio único. La última sección está dedicada a la nueva posibilidad deaplicación de microhilos recubiertos de vidrio en compuestos inteligentes con microhilos integrados

Ferromagnetic Composite Wire Inductors

Ph.DDOCTOR OF PHILOSOPH

A Novel Variable Geometry based Planar Inductor Design for Wireless Charging Application

In this thesis, the performance, modelling and application of a planar electromagnetic coil are discussed. Due to the small size profiles and their non‐contact nature, planar coils are widely used due to their simple and basic design. The uncertain parameters have been identified and simulated using ANSYS that has been run utilising a newly developed MATLAB code. This code has made it possible to run thousands of trials without the need to manually input the various parameters for each run. This has facilitated the process of obtaining all the probable solutions within the defined range of properties. The optimum and robust design properties were then determined. The thesis discusses the experimentation and the finite element modelling (FEM) performed for developing the design of planar coils and used in wireless chargers. In addition, the thesis investigates the performance of various topologies of planar coils when they are used in wireless chargers. The ANSYS Maxwell FEM package has been used to analyse the models while varying the topologies of the coils. For this purpose, different models in FEM were constructed and then tested with topologies such as circular, square and hexagon coil configurations. The described methodology is considered as an effective way for obtaining maximum Power transfer efficiency (PTE) with a certain distance on planar coils with better performance. The explored designs studies are, namely: (1) Optimization of Planar Coil Using Multi-core, (2) planar coil with an Orthogonal Flux Guide, (3) Using the Variable Geometry in a Planar coil for an Optimised Performance by using the robust design method, (4) Design and Integration of Planar coil on wireless charger. In the first design study, the aim is to present the behaviour of a newly developed planar coil, built from a Mu-metal, via simulation. The structure consists of an excitation coil, sensing coils and three ferromagnetic cores 2 located on the top, middle and bottom sections of the coil in order to concentrate the field using the iterative optimisation technique. Magnetic materials have characteristics which allows them to influence the magnetic field in its environment. The second design study presents the optimal geometry and material selection for the planar with an Orthogonal Flux Guide. The study demonstrates the optimising of the materials and geometry of the coil that provides savings in terms of material usage as well as the employed electric current to produce an equivalent magnetic field. The third design study presents the variable geometry in a planar inductor to obtain the optimised performance. The study has provided the optimum and robust design parameters in terms of different topologies such as circular, square and hexagon coil configurations and then tested, Once the best topology is chosen based on performance. The originality of the work is evident through the randomisation of the parameters using the developed MATLAB code and the optimisation of the joint performance under defined conditions. Finally, the fourth design study presents the development of the planar coil applications. Three shapes of coils are designed and experimented to calculate the inductance and the maximum power transfer efficiency (PTW) over various spacing distances and frequency

Methodological Reduction of Magnetically Induced Noise in Magnetic Multilayers for Sensor Applications

Current composite magnetoelectric (ME) sensors of cantilever design have shown promising properties and positive tendencies toward sensor applications in biomagnetic sensing. Despite great signal performance, the sensors have limitations, resulting from noise generated by the magnetic phase. The magnetically induced noise dominates the sensors performance even further when low frequency signals are probed, using magnetic frequency conversion (MFC). The work orients around this specific impediment and provides various techniques to suppress the noise sources, originating from the magnetic phase. In the beginning, the work reviews the effectiveness of multilayer exchange bias (EB) systems that were used to reduce magnetic noise. An improvement of the system is introduced that allowed increased signal yield. However, the noise response could not be improved. For this reason, a new magnetic multilayer system dubbed antiparallel exchange bias (APEB) is introduced, which is formed with a specialized post-production heating scheme. The developed coupling allows formation of a stable magnetic configuration, leading to a significant reduction of the magnetic noise. Incorporated into the ME sensors, the APEB yields improvement in their limit of detection (LOD) and reproducibility of their sensing properties. The sensors were characterized electrically as well as magnetically using magneto-optical Kerr effect microscopy. In their finalized form, the sensors exhibit a significantly decreased noise behavior, demonstrating a voltage noise threshold below 10-7 V/Hz1/2 at optimal working parameters at 10 Hz during MFC operation. The sensors demonstrate more than two orders of magnitude and one order of magnitude lower noise level in comparison to conventional single layer sensors and multilayer exchange biased sensors respectively. The sensors demonstrate noise limitations only by the thermo-mechanical noise level with application of MFC. Thickness increase of individual ferromagnetic layers and variation of anisotropy alignment was performed to counteract the reduction of the signal output, whilst upholding the low noise behavior. The new sensors with a total ferromagnetic thickness of 4 µm provided an LOD of 50 pT/Hz1/2 at 10 Hz. Within this work also MOKE analysis of sensor behavior during electrical excitation was performed. The effect and mechanism of the electrical excitation on the domain construct is investigated for single layer as well as multilayer (AP)EB systems. Preliminary measurements of such sensors already indicated an LOD of 30 pT/Hz1/2 at 10 Hz. The final part of the dissertation revolves around the minimization of edge effects that plague the sensor designs and form a major noise source in the magnetic phase. To circumvent this effect, an investigation of various patterned edges was employed in order to induce the stress effect complementary to the desired magnetic anisotropy direction. In conclusion, this work provides significant research in the field of magnetic domain manipulation and magnetic domain stabilization that is not limited in applicability to ME sensors. It spans also to other sensors that utilize magnetic layers for the sensing of magnetic fields. Furthermore, the newly developed concepts could be implemented into other devices utilizing magnetic thin film components such as energy harvesters, magnetic shielding and magnetic recordings.Gegenwärtige magnetoelektrische (ME) Kompositsensoren, die auf einem Biegebalkendesign beruhen, besitzen vielversprechende Eigenschaften bezüglich der Anwendung als Magnetfeldsensor zur Detektion biomagnetischer Signale. Trotz der hohen Signalamplitude weisen diese Sensoren Einschränkungen auf, die auf von der ferromagnetischen Phase erzeugten Rauschbeiträgen beruhen. Diese magnetisch induzierten Rauschbeiträge dominieren die Sensorleistung, insbesondere wenn Niederfrequenzsignale mit der sogenannten magnetischen Frequenzumwandlung (MFC) abgetastet werden. Der Fokus der Arbeit liegt daher auf diesem spezifischen Problem, und es werden verschiedene Techniken aufgezeigt, um die von der magnetischen Phase herrührenden Rauschquellen zu unterdrücken. Zu Beginn der Arbeit wurde die Wirksamkeit von mehrschichtigen Exchange-Bias (EB) Systemen untersucht, die bereits zur Reduktion des magnetischen Rauschens eingesetzt werden. Durch eine Verbesserung des Systems konnte eine erhöhte Signalausbeute ermöglicht, jedoch das Rauschverhalten nicht verbessert werden. Aus diesem Grund wurde ein magnetisches Mehrschichtsystem, "Antiparallel Exchange Bias" (APEB), eingeführt. Das neue System wird mittels einer speziellen Temperaturnachbehandlung hergestellt. Das neu entwickelte Kopplungsschema ermöglicht die Bildung einer stabilen magnetischen Konfiguration, welche zu einer signifikanten Reduzierung des magnetischen Rauschens führt. Zusätzlich verbessert das APEB die Nachweisgrenze (LOD) und die Reproduzierbarkeit der Sensoreigenschaften. Die Charakterisierung der Sensoren wurden sowohl elektrisch als auch magnetisch mittels magneto-optischer Kerr-Effekt (MOKE) Mikroskopie durchgeführt. In ihrer endgültigen Form zeigen die Sensoren ein signifikant verringertes Rauschverhalten unter 10- 7 V/Hz1/2 bei 10 Hz bei optimalen Arbeitsparametern während der Anwendung von MFC. Die Sensoren weisen damit einen mehr als zwei Größenordnungen bzw. eine Größen-ordnung niedrigeren Rauschpegel im Vergleich zu herkömmlichen Einzelschicht-sensoren bzw. herkömmlichen mehrschichtigen EB Sensoren auf. Die Performance der Sensoren ist damit auch bei der Verwendung von MFC nur durch das thermomechanische Rauschen begrenzt. Eine Erhöhung der Schichtdicke der einzelnen ferromagnetischen Schichten sowie eine Variation der magnetischen Anisotropieausrichtung wurden durchgeführt, um der einhergehenden Verringerung der Signalamplitude entgegenzuwirken und dabei trotzdem das rauscharme Verhalten beizubehalten. Die Sensoren mit einer ferromagnetischen Gesamtdicke von 4 µm und angeregt mit MFC lieferten ein LOD von 50 pT/Hz1/2 bei 10 Hz. Im Rahmen dieser Arbeit wurden zusätzliche MOKE-Analysen des Sensorverhaltens während elektrischer Modulation durchgeführt. Der Effekt und Mechanismus der elektrischen Anregung auf das Domänenverhalten wurden sowohl für Einzelschicht-systeme als auch für mehrschichtige EB-Systeme untersucht. Für diese Anregungsmethode wurden auch spezielle APEB Sensoren entwickelt. Vorläufige Messungen der Sensoren zeigten bereits ein LOD von 30 pT/Hz1/2 bei 10 Hz. Der letzte Teil der Dissertation befasst sich mit der Minimierung von Randeffekten, die die Hauptstörquellen in der magnetischen Phase bilden. Um diese Effekte zu umgehen, wurde eine Untersuchung verschiedener Kantenstrukturen zur Induktion des Spannungseffektes komplementär zur gewünschten Anisotropieausrichtung durchgeführt. Zusammenfassend liefert diese Arbeit einen bedeutenden Fortschritt auf dem Gebiet der magnetischen Domänenmanipulation und Domänenstabilisierung, die nicht nur auf ME-Sensoren anwendbar ist, sondern auch auf andere Sensortypen, die Magnetschichten zum Erfassen von Magnetfeldern verwenden. Darüber hinaus könnten die neu entwickelten Konzepte in andere Gebieten implementiert werden, die magnetische Dünnschichtkomponenten verwenden. Dazu gehören sogenannte Energy Harvester, magnetische Abschirmungen und magnetische Datenspeicher

EUROSENSORS XVII : book of abstracts

Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)

Magnetoimpedance Effect in the Ribbon-Based Patterned Soft Ferromagnetic Meander-Shaped Elements for Sensor Application

Amorphous and nanocrystalline soft magnetic materials have attracted much attention in the area of sensor applications. In this work, the magnetoimpedance (MI) effect of patterned soft ferromagnetic meander-shaped sensor elements has been investigated. They were fabricated starting from the cobalt-based amorphous ribbon using the lithography technique and chemical etching. Three-turn (S1: spacing s = 50 μm, width w = 300 μm, length l = 5 mm; S2: spacing s = 50 μm, width w = 400 μm, length l = 5 mm) and six-turn (S3: s = 40 μm, w = 250 μm, length l = 5 mm; S4: s = 40 μm, w = 250 μm and l = 8 mm) meanders were designed. The ‘n’ shaped meander part was denominated as “one turn”. The S4 meander possesses a maximum MI ratio calculated for the total impedance ΔZ/Z ≈ 250% with a sensitivity of about 36%/Oe (for the frequency of about 45 MHz), and an MI ratio calculated for the real part of the total impedance ΔR/R ≈ 250% with the sensitivity of about 32%/Oe (for the frequency of 50 MHz). Chemical etching and the length of the samples had a strong impact on the surface magnetic properties and the magnetoimpedance. A comparative analysis of the surface magnetic properties obtained by the magneto-optical Kerr technique and MI data shows that the designed ferromagnetic meander-shaped sensor elements can be recommended for high frequency sensor applications focused on the large drop analysis. Here we understand a single large drop as the water-based sample to analyze, placed onto the surface of the MI sensor element either by microsyringe (volue range 0.5–500 μL) or automatic dispenser (volume range 0.1–50 mL)