Noninvasive Deep Brain Stimulation via Temporally Interfering Electric Fields.

We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) concept via modeling and physics experiments, and verified that neurons in the living mouse brain could follow the electric field envelope. We demonstrate the utility of TI stimulation by stimulating neurons in the hippocampus of living mice without recruiting neurons of the overlying cortex. Finally, we show that by altering the currents delivered to a set of immobile electrodes, we can steerably evoke different motor patterns in living mice.

Magnetothermal Multiplexing for Selective Remote Control of Cell Signaling.

Magnetic nanoparticles have garnered sustained research interest for their promise in biomedical applications including diagnostic imaging, triggered drug release, cancer hyperthermia, and neural stimulation. Many of these applications make use of heat dissipation by ferrite nanoparticles under alternating magnetic fields, with these fields acting as an externally administered stimulus that is either present or absent, toggling heat dissipation on and off. Here, we motivate and demonstrate an extension of this concept, magnetothermal multiplexing, in which exposure to alternating magnetic fields of differing amplitude and frequency can result in selective and independent heating of magnetic nanoparticle ensembles. The differing magnetic coercivity of these particles, empirically characterized by a custom high amplitude alternating current magnetometer, informs the systematic selection of a multiplexed material system. This work culminates in a demonstration of magnetothermal multiplexing for selective remote control of cellular signaling in vitro.

Current-induced switching of a van der Waals ferromagnet at room temperature.

Recent discovery of emergent magnetism in van der Waals magnetic materials (vdWMM) has broadened the material space for developing spintronic devices for energy-efficient computation. While there has been appreciable progress in vdWMM discovery, a solution for non-volatile, deterministic switching of vdWMMs at room temperature has been missing, limiting the prospects of their adoption into commercial spintronic devices. Here, we report the first demonstration of current-controlled non-volatile, deterministic magnetization switching in a vdW magnetic material at room temperature. We have achieved spin-orbit torque (SOT) switching of the PMA vdW ferromagnet Fe3GaTe2 using a Pt spin-Hall layer up to 320 K, with a threshold switching current density as low as [Formula: see text]1.69 [Formula: see text] 106 A cm-2 at room temperature. We have also quantitatively estimated the anti-damping-like SOT efficiency of our Fe3GaTe2/Pt bilayer system to be [Formula: see text], using the second harmonic Hall voltage measurement technique. These results mark a crucial step in making vdW magnetic materials a viable choice for the development of scalable, energy-efficient spintronic devices.

Cell Rover-a miniaturized magnetostrictive antenna for wireless operation inside living cells.

An intracellular antenna can open up new horizons for fundamental and applied biology. Here, we introduce the Cell Rover, a magnetostrictive antenna which can operate wirelessly inside a living cell and is compatible with 3D biological systems. It is sub-mm in size, acoustically actuated by an AC magnetic field and resonantly operated at low MHz frequencies, which is ideal for living systems. We developed an injection scheme involving non-uniform magnetic fields for intracellular injection of the Cell Rovers and demonstrated their operation in fully opaque, stage VI Xenopus oocytes, for which real-time imaging with conventional technologies is challenging. We also show that they provide a pathway for multiplexing applications to individually address multiple cells or to tune to more than one antenna within the same cell for versatile functionalities. This technology forms the foundation stone that can enable the integration of future capabilities such as smart sensing, modulation as well as energy harvesting to power in-cell nanoelectronic computing and can potentially bring the prowess of information technology inside a living cell. This could lead to unprecedented opportunities for fundamental understanding of biology as well as diagnostics and therapeutics.

Interface-driven chiral magnetism and current-driven domain walls in insulating magnetic garnets.

Magnetic oxides exhibit rich fundamental physics1-4 and technologically desirable properties for spin-based memory, logic and signal transmission5-7. Recently, spin-orbit-induced spin transport phenomena have been realized in insulating magnetic oxides by using proximate heavy metal layers such as platinum8-10. In their metallic ferromagnet counterparts, such interfaces also give rise to a Dzyaloshinskii-Moriya interaction11-13 that can stabilize homochiral domain walls and skyrmions with efficient current-driven dynamics. However, chiral magnetism in centrosymmetric oxides has not yet been observed. Here we discover chiral magnetism that allows for pure spin-current-driven domain wall motion in the most ubiquitous class of magnetic oxides, ferrimagnetic iron garnets. We show that epitaxial rare-earth iron garnet films with perpendicular magnetic anisotropy exhibit homochiral Néel domain walls that can be propelled faster than 800 m s-1 by spin current from an adjacent platinum layer. We find that, despite the relatively small interfacial Dzyaloshinskii-Moriya interaction, very high velocities can be attained due to the antiferromagnetic spin dynamics associated with ferrimagnetic order.

High-performance and scalable on-chip digital Fourier transform spectroscopy.

On-chip spectrometers have the potential to offer dramatic size, weight, and power advantages over conventional benchtop instruments for many applications such as spectroscopic sensing, optical network performance monitoring, hyperspectral imaging, and radio-frequency spectrum analysis. Existing on-chip spectrometer designs, however, are limited in spectral channel count and signal-to-noise ratio. Here we demonstrate a transformative on-chip digital Fourier transform spectrometer that acquires high-resolution spectra via time-domain modulation of a reconfigurable Mach-Zehnder interferometer. The device, fabricated and packaged using industry-standard silicon photonics technology, claims the multiplex advantage to dramatically boost the signal-to-noise ratio and unprecedented scalability capable of addressing exponentially increasing numbers of spectral channels. We further explore and implement machine learning regularization techniques to spectrum reconstruction. Using an 'elastic-D1' regularized regression method that we develop, we achieved significant noise suppression for both broad (>600 GHz) and narrow (<25 GHz) spectral features, as well as spectral resolution enhancement beyond the classical Rayleigh criterion.

Fast current-driven domain walls and small skyrmions in a compensated ferrimagnet.

Spintronics is a research field that aims to understand and control spins on the nanoscale and should enable next-generation data storage and manipulation. One technological and scientific key challenge is to stabilize small spin textures and to move them efficiently with high velocities. For a long time, research focused on ferromagnetic materials, but ferromagnets show fundamental limits for speed and size. Here, we circumvent these limits using compensated ferrimagnets. Using ferrimagnetic Pt/Gd44Co56/TaOx films with a sizeable Dzyaloshinskii-Moriya interaction, we realize a current-driven domain wall motion with a speed of 1.3 km s-1 near the angular momentum compensation temperature (TA) and room-temperature-stable skyrmions with minimum diameters close to 10 nm near the magnetic compensation temperature (TM). Both the size and dynamics of the ferrimagnet are in excellent agreement with a simplified effective ferromagnet theory. Our work shows that high-speed, high-density spintronics devices based on current-driven spin textures can be realized using materials in which TA and TM are close together.

Practical methods for generating alternating magnetic fields for biomedical research.

Alternating magnetic fields (AMFs) cause magnetic nanoparticles (MNPs) to dissipate heat while leaving surrounding tissue unharmed, a mechanism that serves as the basis for a variety of emerging biomedical technologies. Unfortunately, the challenges and costs of developing experimental setups commonly used to produce AMFs with suitable field amplitudes and frequencies present a barrier to researchers. This paper first presents a simple, cost-effective, and robust alternative for small AMF working volumes that uses soft ferromagnetic cores to focus the flux into a gap. As the experimental length scale increases to accommodate animal models (working volumes of 100s of cm3 or greater), poor thermal conductivity and volumetrically scaled core losses render that strategy ineffective. Comparatively feasible strategies for these larger volumes instead use low loss resonant tank circuits to generate circulating currents of 1 kA or greater in order to produce the comparable field amplitudes. These principles can be extended to the problem of identifying practical routes for scaling AMF setups to humans, an infrequently acknowledged challenge that influences the extent to which many applications of MNPs may ever become clinically relevant.

Survival analysis of patients with idiopathic dilated cardiomyopathy in Oman.

OBJECTIVE: To study the 10-year survival of adults with idiopathic dilated cardiomyopathy (IDC) in Oman. METHODS: Ninety-seven patients aged >13 years with IDC attending the Cardiology Unit, Sultan Qaboos University Hospital, Muscat, Oman from 1992-1995 were prospectively studied, in order to identify the outcome and factors contributing to death. RESULTS: Among 97 patients, 2 died from acute heart failure at presentation. The remaining 95 patients were followed up for periods ranging from 1-10 years (median 7 years). Twenty-four out of 95 patients exhibited clinical deterioration with reduced left ventricular ejection fraction (LVEF), by 5-11%, and 17 of them expired due to resistant heart failure. The remaining 71 patients remained stable and did not show deterioration in LVEF; however, 7 of them died suddenly at home possibly from ventricular arrhythmia. The survival rates were 94% at one year (95% confidence interval [CI] 88% to 99%), 86% at 3 years (95% CI 79% to 93%), and 64% at 10 years (95% CI 51% to 78%). Mean survival was 6.5 years (95% CI 6 to 7 years). Multivariate regression analysis revealed that factors related to death were LVEF <30% (p<0.001) and presence of severe mitral regurgitation (p=0.01). CONCLUSION: Outcome of dilated cardiomyopathy has improved due to greater understanding of this condition leading to better therapeutic approach. Resistant heart failure and cardiac arrhythmias remain the main causes of mortality. Poor outcome was related to low LVEF and presence of severe mitral regurgitation.