Quantitative, high-sensitivity measurement of liquid analytes using a smartphone compass.

Smartphone ubiquity has led to rapid developments in portable diagnostics. While successful, such platforms are predominantly optics-based, using the smartphone camera as the sensing interface. By contrast, magnetics-based modalities exploiting the smartphone compass (magnetometer) remain unexplored, despite inherent advantages in optically opaque, scattering or auto-fluorescing samples.

Shaped Magnetogel Microparticles for Multispectral Magnetic Resonance Contrast and Sensing.

Multispectral magnetic resonance imaging (MRI) contrast agents are microfabricated three-dimensional magnetic structures that encode nearby water protons with discrete frequencies. The agents have a unique radiofrequency (RF) resonance that can be tuned by engineering the geometric parameters of these microstructures. Multispectral contrast agents can be used as sensors by incorporating a stimulus-driven shape-changing response into their structure.

Iron oxide nanoparticles as positive T contrast agents for low-field magnetic resonance imaging at 64 mT.

We have investigated the efficacy of superparamagnetic iron oxide nanoparticles (SPIONs) as positive T contrast agents for low-field magnetic resonance imaging (MRI) at 64 millitesla (mT). Iron oxide-based agents, such as the FDA-approved ferumoxytol, were measured using a variety of techniques to evaluate T contrast at 64 mT. Additionally, we characterized monodispersed carboxylic acid-coated SPIONs with a range of diameters (4.

Reflow transfer for conformal three-dimensional microprinting.

From microcircuits to metamaterials, the micropatterning of surfaces adds valuable functionality. For nonplanar surfaces, incompatibility with conventional microlithography requires the transfer of originally planar micropatterns onto those surfaces; however, existing approaches accommodate only limited curvatures. A microtransfer approach was developed using reflowable materials that transform between solid and liquid on demand, freely stretching to yield transfers that naturally conform down to nanoscale radii of curvature and arbitrarily complex topographies.

The misunderstood meander: Redesigning MRI meander-line surface coils to reduce noise, increase uniformity, and eliminate image artifacts.

Meander-line, or zig-zag, MRI surface coils theoretically promise spatially uniform fields with optimal field localization close to the coil. In reality, they suffer poorer than expected field localizations and acquired images are often highly inhomogeneous, plagued by repeating stripe-like signal-loss artifacts. We show that both these detrimental effects arise from coil design based on the same invalid approximation in the underlying theory.

Observation of iron oxide nanoparticle synthesis in magnetogels using magnetic resonance imaging.

We show that magnetic resonance imaging (MRI) can be used to visualize the spatiotemporal dynamics of iron oxide nanoparticle growth within a hydrogel network during in situ coprecipitation. The synthesis creates a magnetic nanoparticle loaded polymer gel, or magnetogel. During in situ coprecipitation, iron oxide nanoparticles nucleate and grow due to diffusion of a precipitating agent throughout an iron precursor loaded polymer network.

Patterned Surface Energy in Elastomeric Molds as a Generalized Approach to Polymer Particle Fabrication.

We present a generic fabrication scheme to produce polymer microparticles with engineerable, complex shapes. The polymer particles are made from polyethylene glycol based hydrogels using a poly(dimethylsiloxane) (PDMS) molding technique. A simple surface treatment is used to pattern the surface energy of the PDMS molds, engendering the recessed wells in the molds with a higher surface energy than that of the surface.

Author Correction: Large T contrast enhancement using superparamagnetic nanoparticles in ultra-low field MRI.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Large T contrast enhancement using superparamagnetic nanoparticles in ultra-low field MRI.

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely investigated and utilized as magnetic resonance imaging (MRI) contrast and therapy agents due to their large magnetic moments. Local field inhomogeneities caused by these high magnetic moments are used to generate T contrast in clinical high-field MRI, resulting in signal loss (darker contrast). Here we present strong T contrast enhancement (brighter contrast) from SPIONs (diameters from 11 nm to 22 nm) as observed in the ultra-low field (ULF) MRI at 0.

Shape-changing magnetic assemblies as high-sensitivity NMR-readable nanoprobes.

Fluorescent and plasmonic labels and sensors have revolutionized molecular biology, helping visualize cellular and biomolecular processes. Increasingly, such probes are now being designed to respond to wavelengths in the near-infrared region, where reduced tissue autofluorescence and photon attenuation enable subsurface in vivo sensing. But even in the near-infrared region, optical resolution and sensitivity decrease rapidly with increasing depth.

Engineering novel detectors and sensors for MRI.

Increasing detection sensitivity and image contrast have always been major topics of research in MRI. In this perspective, we summarize two engineering approaches to make detectors and sensors that have potential to extend the capability of MRI. The first approach is to integrate miniaturized detectors with a wireless powered parametric amplifier to enhance the detection sensitivity of remotely coupled detectors.

Microfabricated high-moment micrometer-sized MRI contrast agents.

While chemically synthesized superparamagnetic microparticles have enabled much new research based on MRI tracking of magnetically labeled cells, signal-to-noise levels still limit the potential range of applications. Here it is shown how, through top-down microfabrication, contrast agent relaxivity can be increased several-fold, which should extend the sensitivity of such cell-tracking studies. Microfabricated agents can benefit from both higher magnetic moments and higher uniformity than their chemically synthesized counterparts, implying increased label visibility and more quantitative image analyses.

Microfabricated multispectral MRI agents: a brief overview.

This paper provides an introductory overview of recent microfabricated, as opposed to traditional chemically synthesized, magnetic resonance imaging (MRI) contrast agents. As a specific example of the enhanced agent functionality that top-down micro-engineering allows, the paper focuses on recently demonstrated magnetic microstructures that provide multispectral MRI contrast.

The fabrication of uniform cylindrical nanoshells and their use as spectrally tunable MRI contrast agents.

A new form of tunable magnetic resonance imaging agent based on precisely dimensioned cylindrical magnetic nanoshells is introduced. Using top-down prepatterned substrates, the nanoshells are fabricated by exploiting what is usually regarded as a detrimental processing side-effect, namely the redeposition of material back-sputtered during ion-milling. The well-resolved nuclear magnetic resonance peaks of the resulting nanostructures attest to the nanoscale fabrication control and the general feasibility of such sputter redeposition for fabrication of a variety of self-supporting, highly monodisperse nanoscale structures.

Micro-engineered local field control for high-sensitivity multispectral MRI.

In recent years, biotechnology and biomedical research have benefited from the introduction of a variety of specialized nanoparticles whose well-defined, optically distinguishable signatures enable simultaneous tracking of numerous biological indicators. Unfortunately, equivalent multiplexing capabilities are largely absent in the field of magnetic resonance imaging (MRI). Comparable magnetic-resonance labels have generally been limited to relatively simple chemically synthesized superparamagnetic microparticles that are, to a large extent, indistinguishable from one another.

Coherent matter-wave manipulation in the diabatic limit.

Guided systems for coherent matter waves are expected to offer substantial improvements over unguided systems, but adiabatic coupler proposals have proven difficult to realize. We outline instead considerations for a coherence-preserving diabatic approach enabling filters, couplers, and interferometers that can accept multimode guide inputs of up to magneto-optical-trap temperatures.