This review describes recent advances in the handling and manipulation of magnetic particles in microfluidic systems. Starting from the properties of magnetic nanoparticles and microparticles, their use in magnetic separation, immuno-assays, magnetic resonance imaging, drug delivery, and hyperthermia is discussed. We then focus on new developments in magnetic manipulation, separation, transport, and detection of magnetic microparticles and nanoparticles in microfluidic systems, pointing out the advantages and prospects of these concepts for future analysis applications.

/pdf/magnetic-bead-handling-on-chip-new-opportunities-for-1dyl8u0499.pdf

Magnetic bead handling on-chip: new opportunities for analytical applications

Keywords: Spin-Valve Sensors ; Cell Tracking Velocimetry ; On-A-Chip ; Polymerase-Chain-Reaction ; Total Analysis Systems ; Iron-Oxide Nanoparticles ; Field-Flow Fractionation ; Cross-Coupling Reactions ; Circulating Tumor-Cells ; Mode Magnetophoretic Microseparator Reference LMIS2-ARTICLE-2010-004doi:10.1021/cr9001929View record in Web of Science Record created on 2010-01-20, modified on 2016-08-08

Microfluidic applications of magnetic particles for biological analysis and catalysis.

Magnetoresistive-based biosensors and biochips.

In this review we discuss conventional methods of performing biological assays and molecular identification and highlight their advantages and limitations. An alternative approach based on magnetic nanotechnology is then presented. Firstly, magnetic carriers are introduced and their biocompatibility and functionalisation discussed, with spotlights on functionalisation via self assembled monolayers and on methods of reducing nonspecific binding. In addition an introduction is provided to the basic physical concepts behind the various types of sensors used to detect magnetic labels. Finally, progress in the field of magnetic biosensors and the outlook for the future are discussed.

Magnetic biosensor technologies for medical applications: a review

Magnetoresistive (MR) sensors have been identified as promising candidates for the development of high-performance magnetometers due to their high sensitivity, low cost, low power consumption, and small size. The rapid advance of MR sensor technology has opened up a variety of MR sensor applications. These applications are in different areas that require MR sensors with different properties. Future MR sensor development in each of these areas requires an overview and a strategic guide. An MR sensor roadmap (non-recording applications) was therefore developed and made public by the Technical Committee of the IEEE Magnetics Society with the aim to provide an research and development (R&D) guide for MR sensors intended to be used by industry, government, and academia. The roadmap was developed over a three-year period and coordinated by an international effort of 22 taskforce members from ten countries and 17 organizations, including universities, research institutes, and sensor companies. In this paper, the current status of MR sensors for non-recording applications was identified by analyzing the patent and publication statistics. As a result, timescales for MR sensor development were established and critical milestones for sensor parameters were extracted in order to gain insight into potential MR sensor applications (non-recording). Five application areas were identified, and five MR sensor roadmaps were established. These include biomedical applications, flexible electronics, position sensing and human–computer interactions, non-destructive evaluation and monitoring, and navigation and transportation. Each roadmap was analyzed using a logistic growth model, and new opportunities were predicted based on the extrapolated curve, forecast milestones, and professional judgment of the taskforce members. This paper provides a framework for MR sensor technology (non-recording applications) to be used for public and private R&D planning, in order to provide guidance into likely MR sensor applications, products, and services expected in the next 15 years and beyond.

/pdf/magnetoresistive-sensor-development-roadmap-non-recording-nb32j30mph.pdf

Magnetoresistive Sensor Development Roadmap (Non-Recording Applications)

Manipulation and detection of magnetic beads on a semiconductor chip opens up new perspectives for analysis of magnetically labeled specimens in biomechanical micro-electromechanical systems for biological applications. Sensitive spin-valve sensors were integrated with magnetic field generating conductors to assess the behavior of ensembles of superparamagnetic nanoparticles 300 nm in diameter that contain 75%–80% magnetite. The spin-valve multilayer including a nanooxide layer achieves 8% magnetoresistance (MR) for an integrated device of 2×16 μm2. Motion of the magnetic particles towards and across the sensor is achieved by two tapered magnetic field generating current conductors. The spin-valve sensor detects the stray magnetic field that emanates from the ensemble of magnetic particles. We study the transients in the magnetic signal on the order of 1% MR. These results lead to a model that describes magnetization configurations of the cluster of beads.

On-chip manipulation and magnetization assessment of magnetic bead ensembles by integrated spin-valve sensors

The present invention is related to a method of producing a semiconductor device and the resulting device. The method is suitable in the first place for producing high power devices, such as High Electron Mobility Transistors (HEMT), in particular HEMT-devices with multiples source-gate-drain groups or multiple base bipolar transistors. According to the method, the interconnect between the source contacts is not produced by air bridge structures, but by etching vias through the semiconductor layer directly to the ohmic contacts and applying a contact layer on the backside of the device.

Method for producing a semiconductor device and resulting device

This paper reports on the fabrication and characterization of Hall and magnetoresistive sensors with high sensitivity and good temperature stability, InAs/AlGaSb quantum well structures grown by molecular beam epitaxy (MBE) on semiinsulating GaAs substrates were used as active layers for magnetic field sensing. The excellent transport properties (electron mobilities up to 30,000 cm/sup 2/Ns at room temperature) resulted in high sensitivity for room temperature operation of magnetoresistors (relative sensitivity of 0.46%/mT) and Hall elements (magnetic sensitivity of 5.5 V/T),.

InAs/(Al,Ga)Sb quantum well structures for magnetic sensors

AlGaN/GaN high electron mobility transistors are very promising for microwave power applications. Integration and packaging of those high power density devices requires specific attention to thermal management, especially when the AlGaN/GaN heterostructures are grown on sapphire substrates. Indeed, the low thermal conductivity of sapphire is limiting the power performance of the devices. To improve the thermal management, we propose to remove the sapphire substrate after the HEMT processing. In this paper we show that the sapphire substrate can be removed using laser lift-off, without any substantial degradation of the HEMT properties. This is a first important step towards a system-in-a-package integration of AlGaN/GaN HEMTs for RF power applications. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Substrate removal of AlGaN/GaN HEMTs using laser lift‐off

Passivation of AlGaN/GaN HEMT by SiN has been shown by several authors to improve device performance. In this paper we demonstrate a new method of passivating the top AlGaN layer, that leads to a drastic improvement of the device characteristics. On top of the AlGaN/GaN HEMT layer structures, a thin SiN layer is grown at high temperature in-situ, i.e. in the MOCVD reactor prior to unloading the HEMT epiwafers. The quality of the SiN is shown to be very high. As the AlGaN surface is protected against any air contamination, ohmic contacts deposited directly on the SiN layer exhibit better properties than on uncapped AlGaN layers. Transistor performance increases impressively: the source-drain dc current, for a positive gate voltage of 2 V, increases from 0.5 A/mm to 1.2 A/mm for similar AlGaN/GaN HEMT structures by depositing SiN in-situ. RF characteristics also show some improvement. The positive impact of in-situ SiN layer has different origins, some being intrinsically linked: surface protection against oxide formation, better ohmic contact formation, passivation of the surface states, reduction of AlGaN relaxation. All this leads to an increase of the 2DEG carrier concentration.

Surface stabilization for higher performance AlGaN/GaN HEMT with in-situ movpe sin

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