Force-Detected Nuclear Magnetic Resonance Independent of Field Gradients (original) (raw)
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Observation of force-detected nuclear magnetic resonance in a homogeneous field
Proceedings of the National Academy of Sciences, 2004
We report the experimental realization of BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient), a sensitive and general method of magnetic resonance. The prototype millimeter-scale NMR spectrometer shows signal and noise levels in agreement with the design principles. We present 1 H and 19 F NMR in both solid and liquid samples, including timedomain Fourier transform NMR spectroscopy, multiple-pulse echoes, and heteronuclear J spectroscopy. By measuring a 1 H-19 F J coupling, this last experiment accomplishes chemically specific spectroscopy with force-detected NMR. In BOOMERANG, an assembly of permanent magnets provides a homogeneous field throughout the sample, while a harmonically suspended part of the assembly, a detector, is mechanically driven by spin-dependent forces. By placing the sample in a homogeneous field, signal dephasing by diffusion in a field gradient is made negligible, enabling application to liquids, in contrast to other force-detection methods. The design appears readily scalable to m-scale samples where it should have sensitivity advantages over inductive detection with microcoils and where it holds great promise for application of magnetic resonance in biology, chemistry, physics, and surface science. We briefly discuss extensions of the BOOMERANG method to the m and nm scales.
Force-detected magnetic resonance without field gradients
Solid State Nuclear Magnetic Resonance, 1998
. A novel method of nuclear magnetic resonance NMR is described which promises to be preferable to known general methods at sample length scales below ; 100 mm. Its advantages stem from the seemingly paradoxical combination of a homogeneous static magnetic field and detection of a mechanical force between a spin-bearing sample and a magnet Ž . assembly. In contrast to other methods of force-detected nuclear magnetic resonance FDNMR , the method is characterized Ž . by better observation of magnetization, enhanced resolution, and no g radient BOOMERANG , and it is generally applicable with respect to sample composition, pulse sequence, and magnetic field strength. Further advantages of portability and low cost stem from the small instrument volume and mass and promise to extend the use of NMR to new applications and environments. A sensitivity analysis, relevant to spectroscopy or imaging, quantifies the advantage of BOOMERANG relative to magnetic induction using microcoils and to FDNMR methods that rely on large gradients of the magnetic field at the sample. q 1998 Elsevier Science B.V.
Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor
Proceedings of the National Academy of Sciences, 2008
We report the detection of nuclear magnetic resonance (NMR) using an anisotropic magnetoresistive (AMR) sensor. A ''remotedetection'' arrangement was used in which protons in flowing water were prepolarized in the field of a superconducting NMR magnet, adiabatically inverted, and subsequently detected with an AMR sensor situated downstream from the magnet and the adiabatic inverter. AMR sensing is well suited for NMR detection in microfluidic ''lab-on-a-chip'' applications because the sensors are small, typically on the order of 10 m. An estimate of the sensitivity for an optimized system indicates that Ϸ6 ؋ 10 13 protons in a volume of 1,000 m 3 , prepolarized in a 10-kG magnetic field, can be detected with a signal-to-noise ratio of 3 in a 1-Hz bandwidth. This level of sensitivity is competitive with that demonstrated by microcoils in superconducting magnets and with the projected sensitivity of microfabricated atomic magnetometers.
Recent Developments in Magnetic Diagnostic Systems
Chemical reviews, 2015
This section reviews various MNP-based bioassay systems. We broadly categorized them as magnetic sensors and actuators, according to their primary use of MNPs, and discuss representative examples in each category. 2.1. Magnetic detection Signals from MNP-labeled biological objects are often measured by magnetometers. 37 Based on the detection mechanism, magnetometers can be categorized into volumetric or surface-based sensors. 38 The volumetric sensors measure analytical signals coming from the entire detection volume, which makes assays simple and fast. The sensors' resolving power, however, can be restricted, because the acquired signal is an ensemble average of the whole volume. Representative examples of volumetric sensors include NMR devices, magnetic susceptometors, and conventional superconducting-quantum-interference-devices (SQUIDs). Surface-based sensors directly detect individual magnetic objects near the sensing elements. These sensors generally achieve higher sensitivity and finer resolution than volumetric ones, but target samples should be placed in close proximity of the sensor surface. Such an arrangement limits the assay configuration, and typically causes the assays to be more time-Lee et al.
Capacitor-based detection of nuclear magnetization: Nuclear quadrupole resonance of surfaces
Journal of Magnetic Resonance, 2011
We demonstrate excitation and detection of nuclear magnetization in a nuclear quadrupole resonance (NQR) experiment with a parallel plate capacitor, where the sample is located between the two capacitor plates and not in a coil as usually. While the sensitivity of this capacitor-based detection is found lower compared to an optimal coil-based detection of the same amount of sample, it becomes comparable in the case of very thin samples and even advantageous in the proximity of conducting bodies. This capacitor-based setup may find its application in acquisition of NQR signals from the surface layers on conducting bodies or in a portable tightly integrated nuclear magnetic resonance sensor.
AIP Advances, 2017
In this work a systematic identification of factors contributing to signal ringing in unilateral nuclear magnetic resonance (NMR) sensors is conducted. Resonant peaks that originate due to multiple factors such as NMR, electrical, magneto-acoustic, core material response, eddy currents and other factors were observed. The peaks caused by the measurement system or electrical resonances and induced magnet vibrations are further analyzed. They appear in every measurement and are considered as interference to signals received from the magnetic core. Forming a distinction between different peaks is essential in identifying the primary contribution to the captured resonant signal. The measurements for the magnetic core indicate that the magnetization induced resonant peaks of the core have relatively higher amplitudes and shorter decay times at low frequencies.
NMR detection with an atomic magnetometer
Physical review letters, 2005
We demonstrate detection of NMR signals using a noncryogenic atomic magnetometer and describe several novel applications of this technique. A nuclear spin-precession signal from water is detected using a spin-exchange-relaxation-free potassium magnetometer. We also demonstrate detection of less than 10(13) 129Xe atoms whose NMR signal is enhanced by a factor of 540 due to Fermi-contact interaction with K atoms. The possibility of using a multichannel atomic magnetometer for fast 3D magnetic resonance imaging is also discussed.
Unilateral NMR with a barrel magnet
Journal of Magnetic Resonance, 2017
Unilateral NMR can examine samples without regard to sample size. It is also an easy path to mobile or portable NMR as well as inexpensive NMR. The objective of this work was to develop unilateral NMR with an improved performance in a sample region that was remote from the apparatus. This was accomplished with the creation of a saddle point where all second derivatives of the main component of the field were nulled. A ∼10cm diameter ∼5cm thick magnet combined with a gradiometer coil on the surface detected signals from a sensitive region that extended ∼2cm from the magnet. The relatively homogeneous field of these unilateral NMR devices allows the measurement of rapidly diffusing spins as well as the use of smaller RF amplifiers, which enhances system mobility.
Biosensing Using Magnetic Particle Detection Techniques
Sensors (Basel, Switzerland), 2017
Magnetic particles are widely used as signal labels in a variety of biological sensing applications, such as molecular detection and related strategies that rely on ligand-receptor binding. In this review, we explore the fundamental concepts involved in designing magnetic particles for biosensing applications and the techniques used to detect them. First, we briefly describe the magnetic properties that are important for bio-sensing applications and highlight the associated key parameters (such as the starting materials, size, functionalization methods, and bio-conjugation strategies). Subsequently, we focus on magnetic sensing applications that utilize several types of magnetic detection techniques: spintronic sensors, nuclear magnetic resonance (NMR) sensors, superconducting quantum interference devices (SQUIDs), sensors based on the atomic magnetometer (AM), and others. From the studies reported, we note that the size of the MPs is one of the most important factors in choosing a ...
Micromagnetic simulations on detection of magnetic labelled biomolecules using MR sensors
Journal of Magnetism and Magnetic Materials, 2009
In this work, we present a study of the interaction between the magnetic particles used in biological applications and the giant magnetoresistive effect (GMR) sensor. The fractional change in resistance, and hence the sensitivity, will be maximized by matching, as far as possible, the size of the sensor to the size of the beads and by carefully positioning the beads over the sensor. We found, by micromagnetic simulations, that the amount of the surface coverage with magnetic particles may affect the magnetization curve of the sensor and will change the field dependence of the GMR response.