This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

http://science.sciencemag.org/content/sci/294/5546/1488.full.pdf

Spintronics: a spin-based electronics vision for the future.

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

/pdf/spintronics-fundamentals-and-applications-2dx38n6phu.pdf

Spintronics: Fundamentals and applications

Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate interplay between surface nano-architectures, surface functionalization and the chosen sensor transducer principle, as well as the usefulness of complementary characterization tools to interpret and to optimize the sensor response.

/pdf/electrochemical-biosensors-sensor-principles-and-5i1lr0kwi6.pdf

Electrochemical Biosensors - Sensor Principles and Architectures

Fundamental and applied research in chemistry and biology benefits from opportunities provided by droplet-based microfluidic systems. These systems enable the miniaturization of reactions by compartmentalizing reactions in droplets of femoliter to microliter volumes. Compartmentalization in droplets provides rapid mixing of reagents, control of the timing of reactions on timescales from milliseconds to months, control of interfacial properties, and the ability to synthesize and transport solid reagents and products. Droplet-based microfluidics can help to enhance and accelerate chemical and biochemical screening, protein crystallization, enzymatic kinetics, and assays. Moreover, the control provided by droplets in microfluidic devices can lead to new scientific methods and insights.

/pdf/reactions-in-droplets-in-microfluidic-channels-22iig0bcxm.pdf

Reactions in Droplets in Microfluidic Channels

Spinels with the formula of AB2O4 (where A and B are metal ions) and the properties of magnetism, optics, electricity, and catalysis have taken significant roles in applications of data storage, biotechnology, electronics, laser, sensor, conversion reaction, and energy storage/conversion, which largely depend on their precise structures and compositions. In this review, various spinels with controlled preparations and their applications in oxygen reduction/evolution reaction (ORR/OER) and beyond are summarized. First, the composition and structure of spinels are introduced. Then, recent advances in the preparation of spinels with solid-, solution-, and vapor-phase methods are summarized, and new methods are particularly highlighted. The physicochemical characteristics of spinels such as their compositions, structures, morphologies, defects, and substrates have been rationally regulated through various approaches. This regulation can yield spinels with improved ORR/OER catalytic activities, which can furth...

Spinels: Controlled Preparation, Oxygen Reduction/Evolution Reaction Application, and Beyond

Low-frequency noise was measured in the frequency range from 0.1Hzto10kHz on a variety of commercially available magnetic sensors. The types of sensors investigated include anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR) effect devices. The 1∕f noise components of electronic and magnetic origin are identified by measuring sensor noise and sensitivity at various applied magnetic fields. Commercial magnetometers typically consist of four elements in a Wheatstone bridge configuration and are biased with either a constant voltage or current. Voltage fluctuations at the sensor output are amplified by a pair of battery powered low-noise preamplifiers and input to a spectrum analyzer. A two-channel cross-correlation technique is used when the performance of a single preamplifier is not sufficient. For the AMR and GMR sensors investigated, both electronic and magnetic components contribute to the overall sensor noise. Maximum noise occurs at the bias field wh...

/pdf/low-frequency-noise-measurements-on-commercial-34fgkojtz7.pdf

Low-frequency noise measurements on commercial magnetoresistive magnetic field sensors

A ferromagnetic thin-film based digital memory cell with a memory film of an anisotropic ferromagnetic material and with a source layer positioned on one side thereof so that a majority of conduction electrons passing therefrom have a selected spin orientation to be capable of reorienting the magnetization of the film. A disruption layer is positioned on the other side of the memory film so that conduction electrons spins passing therefrom are substantially random in orientation. The magnitude of currents needed to operate the cell can be reduced using coincident thermal pulses to raise the cell temperature.

Current switched magnetoresistive memory cell

Commercially available superparamagnetic nanospheres are commonly used in a wide range of biological applications, particularly in magnetically assisted separations. A new and potentially significant technology involves the use of these particles as labels in magnetoresistive assay applications. In these assays, magnetic bead labels are used like fluorescent labels except that the beads are excited and detected with magnetic fields rather than with photons. A major advantage of this technique is that the means for excitation and detection are easily integrable on a silicon circuit. A preliminary study of this technique demonstrated its basic feasibility, and projected a sensitivity of better than 10−12 molar [Baselt et al., Biosensors Bioelectronic 13, 731 (1998)]. In this article we examine the theoretical signal to noise ratio of this type of assay for the special case of a single magnetic bead being detected by a single giant magnetoresistive (GMR) detector. Assuming experimentally observed and reasona...

/pdf/model-for-detection-of-immobilized-superparamagnetic-1ryw6da0vd.pdf

Model for detection of immobilized superparamagnetic nanosphere assay labels using giant magnetoresistive sensors

Method and apparatus for manipulating and monitoring analyte flowing in fluid streams. A giant magnetoresistive sensor has an array of sensing elements that produce electrical output signals which vary in dependence on changes in the magnetic field proximate the sensing elements. The analyte is included in a stream, such that the stream has a magnetic property which is dependent on the concentration and distribution on the analyte therein. The stream is flowed past the giant magnetoresistive sensor and in sufficiently close proximity to cause the magnetic properties of the stream to produce electrical output signals. The electrical output signals are monitored as an indicator of analyte concentration or distribution in the stream flowing past the GMR sensor. Changes in the magnetic field produced by the background stream are introduced by analyte molecules, whose presence in the flow past the GMR will effect the output reading.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1197&context=patents

Method and apparatus for magnetoresistive monitoring of analytes in flow streams

A ferromagnetic thin-film based magnetic field detection system used for detecting the presence of selected molecular species. A magnetic field sensor supported on a substrate has a binding molecule layer positioned on a side thereof capable of selectively binding to the selected molecular species. The magnetic field sensor can be substantially covered by an electrical insulating layer having a recess therein adjacent to the sensor in which the binding molecule layer is provided. An electrical interconnection conductor can be supported on the substrate at least in part between the sensor and the substrate, and is electrically connected to the sensor. The magnetic field sensor can be provided in a bridge circuit, and can be formed by a number of interconnected individual sensors.

Magnetizable bead detector

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