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Advanced Science (Weinheim,... Sep 2023Limbless crawling on land requires breaking symmetry of the friction with the ground and exploiting an actuation mechanism to generate propulsive forces. Here, kirigami...
Limbless crawling on land requires breaking symmetry of the friction with the ground and exploiting an actuation mechanism to generate propulsive forces. Here, kirigami cuts are introduced into a soft magnetic sheet that allow to achieve effective crawling of untethered soft robots upon application of a rotating magnetic field. Bidirectional locomotion is achieved under clockwise and counterclockwise rotating magnetic fields with distinct locomotion patterns and crawling speed in forward and backward propulsions. The crawling and deformation profiles of the robot are experimentally characterized and combined with detailed multiphysics numerical simulations to extract locomotion mechanisms in both directions. It is shown that by changing the shape of the cuts and orientation of the magnet the robot can be steered, and if combined with translational motion of the magnet, complex crawling paths are programed. The proposed magnetic kirigami robot offers a simple approach to developing untethered soft robots with programmable motion.
PubMed: 37357135
DOI: 10.1002/advs.202301895 -
Science Advances Dec 2023Current-induced self-sustained magnetization oscillations in spin-torque nano-oscillators (STNOs) are promising candidates for ultra-agile microwave sources or...
Current-induced self-sustained magnetization oscillations in spin-torque nano-oscillators (STNOs) are promising candidates for ultra-agile microwave sources or detectors. While usually STNOs behave as a monochromatic source, we report here clear bimodal simultaneous emission of incommensurate microwave oscillations in the frequency range of 6 to 10 gigahertz at femtowatt level power. These two tones correspond to two parametrically coupled eigenmodes with tunable splitting. The emission range is crucially sensitive to the change in hybridization of the eigenmodes of free and fixed layers, for instance, through a slight tilt of the applied magnetic field from the normal of the nanopillar. Our experimental findings are supported both analytically and by micromagnetic simulations, which ascribe the process to four-magnon scattering between a pair of radially symmetric magnon modes and a pair of magnon modes with opposite azimuthal index. Our findings pave the way for enhanced cognitive telecommunications and neuromorphic systems that use frequency multiplexing to improve communication performance.
PubMed: 38091395
DOI: 10.1126/sciadv.adk1430 -
Scientific Reports Feb 2024Over the past 15 years, there has been a noticeable uptick in incidents involving children ingesting multiple magnetic foreign bodies which can cause injuries and... (Observational Study)
Observational Study
Over the past 15 years, there has been a noticeable uptick in incidents involving children ingesting multiple magnetic foreign bodies which can cause injuries and gastrointestinal complications including death. The current study aimed to identify the prevalence, clinical presentation, and management of single or multiple magnet ingestions. A retrospective multi-central cross-sectional study was conducted to include all pediatric patients < 18 years presented to the emergency department with ingestion of single or multiple magnets and admitted across hospitals in Qatar, UAE, KSA, Tunisia, and Turkey between January 2011 and December 2021. Demographics, symptoms, management, and outcomes were analyzed. There were 189 magnet ingestions, of which 88 (46.6%) were multiple magnet ingestions. Most patients (55.6%) were male, and the median age was 3.9 (IQR 2-7) years. An abdominal X-ray was obtained in all cases. 119 (62%) patients were conservatively treated, 53 (28%) required surgical intervention and 17 (8.9%) underwent gastroscopy. None of the patients with single magnet ingestions experienced morbidity or severe outcomes. Multiple magnet ingestions led to significant morbidity including hospitalizations, perforations (44.3%), severe intestinal necrosis (19.3%), peritonitis (13.6%), severe abdominal infection (10.2%), and septic shock (4.5%). The rate of surgical intervention (59.1% vs. 1.0%) and gastroscopy (15.9% vs. 3.0%) was significantly higher in the multiple ingestion group compared to the single magnet ingestion group. No deaths were identified. A high risk of serious complications, including the need for surgery to remove the magnets and substantial morbidity may result from swallowing more than one magnet. Magnet safety requirements, public education, and improved legislation are urgently required.
Topics: Humans; Child; Male; Child, Preschool; Female; Magnets; Retrospective Studies; Cross-Sectional Studies; Foreign Bodies; Eating
PubMed: 38403623
DOI: 10.1038/s41598-024-55127-0 -
Lab on a Chip Nov 2023Electrical stimulation of brain tissue slices has been a method used to understand mechanisms imparted by transcranial direct current stimulation (tDCS), but there are...
Electrical stimulation of brain tissue slices has been a method used to understand mechanisms imparted by transcranial direct current stimulation (tDCS), but there are significant direct current electric field (dcEF) dosage and electrochemical by-product concerns in conventional experimental setups that may impact translational findings. Therefore, we developed an on-chip platform with fluidic, electrochemical, and magnetically-induced spatial control. Fluidically, the chamber geometrically confines precise dcEF delivery to the enclosed brain slice and allows for tissue recovery in order to monitor post-stimulation effects. Electrochemically, conducting hydrogel electrodes mitigate stimulation-induced faradaic reactions typical of commonly-used metal electrodes. Magnetically, we applied ferromagnetic substrates beneath the tissue and used an external permanent magnet to enable rotational control in relation to the dcEF. By combining the microfluidic chamber with live-cell calcium imaging and electrophysiological recordings, we showcased the potential to study the acute and lasting effects of dcEFs with the potential of providing multi-session stimulation. This on-chip bioelectronic platform presents a modernized yet simple solution to electrically stimulate explanted tissue by offering more environmental control to users, which unlocks new opportunities to conduct thorough brain stimulation mechanistic investigations.
Topics: Transcranial Direct Current Stimulation; Brain; Electrodes; Electric Stimulation; Lab-On-A-Chip Devices
PubMed: 37909911
DOI: 10.1039/d3lc00492a -
Nature Communications Apr 2024Phase diagrams of materials are typically based on a static order parameter, but it faces challenges when distinguishing subtle phase changes, such as re-ordering. Here,...
Phase diagrams of materials are typically based on a static order parameter, but it faces challenges when distinguishing subtle phase changes, such as re-ordering. Here, we report a dynamic nonequilibrium order parameter termed re-order parameter to determine subtle phases and their transitions in interacting magnets. The dynamical precession of magnetization, so-called magnon, premises as a reliable re-order parameter of strong spin-orbit coupled magnets. We employ orthoferrites YFeO and its Mn-doped variations, where diverse magnetic phases, including canted antiferromagnetic (Γ) and collinear antiferromagnetic (Γ) states, have been well-established. Low-energy magnon uncovers the spin-orbit coupling-induced subtle magnetic structures, resulting in distinct terahertz emissions. The temporal and spectral parameters of magnon emission exhibit characteristics akin to BCS-type order parameters, constructing the magnetic phase diagram of Mn-doped YFeO. This approach further reveals a concealed ferrimagnetic phase within the Γ state, underscoring its potential to search for hidden phases of materials, completing their phase diagrams.
PubMed: 38632266
DOI: 10.1038/s41467-024-47637-2 -
Nature Feb 2024Lifted Kramers spin degeneracy (LKSD) has been among the central topics of condensed-matter physics since the dawn of the band theory of solids. It underpins established...
Lifted Kramers spin degeneracy (LKSD) has been among the central topics of condensed-matter physics since the dawn of the band theory of solids. It underpins established practical applications as well as current frontier research, ranging from magnetic-memory technology to topological quantum matter. Traditionally, LKSD has been considered to originate from two possible internal symmetry-breaking mechanisms. The first refers to time-reversal symmetry breaking by magnetization of ferromagnets and tends to be strong because of the non-relativistic exchange origin. The second applies to crystals with broken inversion symmetry and tends to be comparatively weaker, as it originates from the relativistic spin-orbit coupling (SOC). A recent theory work based on spin-symmetry classification has identified an unconventional magnetic phase, dubbed altermagnetic, that allows for LKSD without net magnetization and inversion-symmetry breaking. Here we provide the confirmation using photoemission spectroscopy and ab initio calculations. We identify two distinct unconventional mechanisms of LKSD generated by the altermagnetic phase of centrosymmetric MnTe with vanishing net magnetization. Our observation of the altermagnetic LKSD can have broad consequences in magnetism. It motivates exploration and exploitation of the unconventional nature of this magnetic phase in an extended family of materials, ranging from insulators and semiconductors to metals and superconductors, that have been either identified recently or perceived for many decades as conventional antiferromagnets.
PubMed: 38356066
DOI: 10.1038/s41586-023-06907-7 -
IScience Sep 2023The emergence of two-dimensional (2D) van der Waals magnets provides an exciting platform for exploring magnetism in the monolayer limit. Exotic quantum phenomena and... (Review)
Review
The emergence of two-dimensional (2D) van der Waals magnets provides an exciting platform for exploring magnetism in the monolayer limit. Exotic quantum phenomena and significant potential for spintronic applications are demonstrated in 2D magnetic crystals and heterostructures, which offer unprecedented possibilities in advanced formation technology with low power and high efficiency. In this review, we summarize recent advances in 2D van der Waals magnetic crystals. We focus mainly on van der Waals materials of truly 2D nature with intrinsic magnetism. The detection methods of 2D magnetic materials are first introduced in detail. Subsequently, the effective strategies to modulate the magnetic behavior of 2D magnets (e.g., Curie temperature, magnetic anisotropy, magnetic exchange interaction) are presented. Then, we list the applications of 2D magnets in the spintronic devices. We also highlight current challenges and broad space for the development of 2D magnets in further studies.
PubMed: 37664598
DOI: 10.1016/j.isci.2023.107584 -
Scientific Reports Aug 2023Maglevs are typically accelerated using electromagnetic propulsion and levitation. High-temperature superconducting (HTS) magnets along with electrodynamic suspension...
Maglevs are typically accelerated using electromagnetic propulsion and levitation. High-temperature superconducting (HTS) magnets along with electrodynamic suspension (EDS) and linear synchronous motors are one of the best options for Hyperloop. However, the strong magnetic fields generated by HTS magnets on the pods inevitably interact with the magnetic and conductive structures in the vacuum tubes, along with the tube itself, while the pods move through the tubes. This interaction is observed as a drag force on the pods, significantly reducing the propulsion efficiency. This study comprehensively analyzes the electromagnetic drag force (EDF) generated by HTS magnets on pods, which accounts for most of the drag forces faced by Hyperloop. Theoretical analysis and 3D FEA simulations are performed to analyze the propulsion forces with HTS magnets and all the drag forces on the pods. The EDF generated by AISI 1010 steel rebars in concrete guideways is even greater than the designed propulsion forces of 40 kN. Consequently, high-manganese (Hi-Mn) steel and insulated steel rebars are adopted and analyzed using 3D FEA simulations. The EDFs generated by the AISI 1010 steel and Hi-Mn steel vacuum tubes are determined by varying the distance between the HTS magnets and tubes at 50 and 1200 km/h, respectively; a minimum distance of 0.75 m is determined by a drag force below 8 kN within their operating velocities. Lastly, the total EDFs of the AISI 1010 steel and Hi-Mn steel tubes with EDS rails are obtained through the optimal design of rebars and tubes. The simulation results show that the total EDFs can be significantly reduced to below 10 kN (approximately 25% of the designed propulsion force after the levitation of pods).
PubMed: 37537338
DOI: 10.1038/s41598-023-39916-7 -
Frontiers in Bioengineering and... 2023Hyperthermia therapy is a hotspot because of its minimally invasive treatment process and strong targeting effect. Herein, a synergistic magnetic and photothermal...
Hyperthermia therapy is a hotspot because of its minimally invasive treatment process and strong targeting effect. Herein, a synergistic magnetic and photothermal therapeutic nanoplatform is rationally constructed. The well-dispersive mSiO-SmCo nanoparticles (NPs) were synthesized through a one-step procedure with the regulated theoretical molar ratio of Sm/Co among 1:1, 1:2, and 1:4 for controlling the dispersion and magnetism properties of SmCo NPs growth in the pore structure of mesoporous SiO (mSiO), where mSiO with diverse porous structures and high specific surface areas serving for locating the permanent magnetic SmCo NPs. The mSiO-SmCo (Sm/Co = 1:2) NPs with highly dispersed and uniform morphology has an average diameter of ∼73.08 nm. The photothermal conversion efficiency of mSiO-SmCo (Sm/Co = 1:2) NPs was determined to be nearly 41%. The further and anti-tumor evaluation of mSiO-SmCo (Sm/Co = 1:2) NPs present promising potentials for hyperthermia-induced tumor therapy due to magnetic and photothermal effects.
PubMed: 37576992
DOI: 10.3389/fbioe.2023.1249775 -
World Journal of Gastrointestinal... Mar 2024Despite much work having been conducted on magnetic compression anastomosis (MCA) in the digestive tract, there are no reports on the influence of magnetic force on the...
BACKGROUND
Despite much work having been conducted on magnetic compression anastomosis (MCA) in the digestive tract, there are no reports on the influence of magnetic force on the anastomosis.
AIM
To investigate the effect of different magnetic force magnets on the MCA of the digestive tract.
METHODS
Two groups of magnets of the same sizes but different magnetic forces were designed and produced. A total of 24 Sprague-Dawley rats were randomly assigned into two groups (powerful magnet group and common magnet group), with 12 rats in each group. Two types of magnets were used to complete the colonic side-to-side anastomosis of the rats. The operation time and magnet discharge time were recorded. The anastomotic specimens were obtained 4 wk after the operation and then the burst pressure and diameter of the anastomosis were measured, and the anastomosis was observed the naked eye and subjected to histological examination.
RESULTS
The magnetic forces of the powerful and common magnet groups at zero distance were 8.26 N and 4.10 N, respectively. The colonic side-to-side anastomosis was completed in all 24 rats, and the operation success rate and postoperative survival rate were 100%. No significant difference was noted in the operation time between the two groups. The magnet discharge time of the powerful magnet group was slightly longer than that of the common magnet group, but the difference was not statistically significant ( = 0.513). Furthermore, there was no statistical difference in the burst pressure ( = 0.266) or diameter of magnetic anastomosis ( = 0.095) between the two groups. The gross specimens of the two groups showed good anastomotic healing, and histological observation indicated good mucosal continuity without differences on healing.
CONCLUSION
In the rat colonic side-to-side MCA model, both the powerful magnet with 8.26 N and the common magnet with 4.10 N showed no significant impact on the anastomosis establishment process or its effect.
PubMed: 38577092
DOI: 10.4240/wjgs.v16.i3.860