Domaines magnétiques concentriques dans des disques nanométriques de Permalloy à structure colonnaire

International audienceWe conducted a thorough experimental and numerical study of the micromagnetic properties of Permalloy (Ni80Fe20) microdisks exhibiting target domain structures at remanence. Vortex configurations are quite common in such microdisks and correspond to an in-plane flux closure configuration of cylindrical symmetry with an out-of-plane magnetized core. In contrast, target domain configuration are observed in thicker microdisks and are characterized by a vortex configuration of the in-plane component of the magnetization superposed to an out-of-plane component of magnetization which oscillates as a function of the distance to the microdisk center resulting in the formation of concentric domains. The ratio of the out-of-plane oscillatory component of the magnetization to the in-plane vortex one increases with the thickness of the microdisk. Hysteresis loops were measured under in-plane and out-of-plane field. The results at remanence and under magnetic field could be interpreted by micromagnetic simulations in which the microdisks were described as an assembly of partially coupled columns representing the granular nanostructure of the films from which the microdisks were patterned. Quite original magnetization processes take place in these microdisks exhibiting target domain remanent configuration. These include in particular entire flipping of the domain configuration and annihilation/creation of ring domains

Microstructured Magnetoelastic Membrane for Magnetic Bioactuators and Soft Artificial Muscles Applications

International audienceIn the growing field of mechanobiology, artificial mechano-reactive systems playan essential role in the generation of mechanical forces and control of materialdeformations. Free-standing magnetic nanoparticles have been studied for themechanical stimulation of living cells. Magnetic composite materials are alsoused to mimic muscles at macroscale. In this study, a new magnetically actuatedmembrane is focused, which can be used for various applications in soft roboticsor as a bioreactor. It consists of a few microns thick polydimethylsiloxane (PDMS)membrane in which an array of magnetic microdisks is embedded. Thesemembranes have a large tuneable flexibility, and they are transparent, biocompatible,and waterproof. They are usable in biology and optics, bothpotentially combined. The membrane deformations under magnetic field havebeen experimentally characterized and modeled. By growing pancreatic cells onsuch membranes, it has been demonstrated that insulin production from the cellscan be enhanced thanks to the mechanical stimulation of the cells provided bythe actuated membrane

Triggering the apoptosis of targeted human renal cancer cells by the vibration of anisotropic magnetic particles attached to the cells membrane

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Fabrication and control of synthetic antiferromagnetic nanoparticles released in solution for biological applications.

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Comparison of self polarization effects in synthetic antiferromagnetic and vortex magnetic microparticles and their use for triggering cancer cells apoptosis

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One-Step Soft Chemical Synthesis of Magnetite Nanoparticles under Inert Gas Atmosphere. Magnetic Properties and In Vitro Study

International audienceIron oxide nanoparticles have received remarkable attention in different applications. For biomedical applications, they need to possess suitable core size, acceptable hydrodynamic diameter, high saturation magnetization, and reduced toxicity. Our aim is to control the synthesis parameters of nanostructured iron oxides in order to obtain magnetite nanoparticles in a single step, in environmentally friendly conditions, under inert gas atmosphere. The physical-chemical, structural, magnetic, and biocompatible properties of magnetite prepared by hydrothermal method in different temperature and pressure conditions have been explored. Magnetite formation has been proved by Fourier-transform infrared spectroscopy and X-ray diffraction characterization. It has been found that crystallite size increases with pressure and temperature increase, while hydrodynamic diameter is influenced by temperature. Magnetic measurements indicated that the magnetic core of particles synthesized at high temperature is larger, in accordance with the crystallite size analysis. Particles synthesized at 100 °C have nearly identical magnetic moments, at 20 × 10 3 μB, corresponding to magnetic cores of 10-11 nm, while the particles synthesized at 200 °C show slightly higher magnetic moments (25 × 10 3 μB) and larger magnetic cores (13 nm). Viability test results revealed that the particles show only minor intrinsic toxicity, meaning that these particles could be suited for biomedical applications

Cancer treatment by magneto-mechanical effect of particles, a review

International audienceCancer treatment by magneto-mechanical effect of particles (TMMEP) is a growing field of research. The principle of this technique is to apply a mechanical force on cancer cells in order to destroy them thanks to magnetic particles vibrations. For this purpose, magnetic particles are injected in the tumor or exposed to cancer cells and a low-frequency alternating magnetic field is applied. This therapeutic approach is quite new and a wide range of treatment parameters are explored to date, as described in the literature. This review explains the principle of the technique, summarizes the parameters used by the different groups and reports the main in vitro and in vivo results

Magneto-optical micromechanical systems for magnetic field mapping

International audienceA new method for magnetic field mapping based on the optical response of organized dense arrays of flexible magnetic cantilevers is explored. When subjected to the stray field of a magnetized material, the mobile parts of the cantilevers deviate from their initial positions, which locally changes the light reflectivity on the magneto-optical surface, thus allowing to visualize the field lines. While the final goal is to be able to map and quantify non-uniform fields, calibrating and testing the device can be done with uniform fields. Under a uniform field, the device can be assimilated to a magnetic-field-sensitive diffraction grating, and therefore, can be analyzed by coherent light diffraction. A theoretical model for the diffraction patterns, which accounts for both magnetic and mechanical interactions within each cantilever, is proposed and confronted to the experimental data

Optical Response of Magnetically Actuated Biocompatible Membranes

International audienceBiocompatible suspended magneto-elastic membranes were prepared. They consist of PDMS (Polydimethylsiloxane) films, with embedded arrays of micrometric magnetic pillars made by lithography techniques. For visible light wavelengths, our membranes constitute magnetically tunable optical diffraction gratings, in transmission and reflection. The optical response has been quantitatively correlated with the membrane structure and deformation, through optical and magneto-mechanical models. In contrast to the case of planar membranes, the diffraction patterns measured in reflection and transmission vary very differently upon magnetic field application. Indeed, the reflected beam is largely affected by the membrane bending, whereas the transmitted beam remains almost unchanged. In reflection, even weak membrane deformation can produce significant changes of the diffraction patterns. This field controlled optical response may be used in adaptive optical applications, photonic devices, as well as for biological applications

Triggering the apoptosis of targeted cancer cells by the mechanical vibrations of synthetic antiferromagnetic or vortex microparticles

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