In silico assessment of electrophysiological neuronal recordings mediated by magnetoelectric nanoparticles

Magnetoelectric materials hold untapped potential to revolutionize biomedical technologies. Sensing of biophysical processes in the brain is a particularly attractive application, with the prospect of using magnetoelectric nanoparticles (MENPs) as injectable agents for rapid brain-wide modulation and recording. Recent studies have demonstrated wireless brain stimulation in vivo using MENPs synthesized from cobalt ferrite (CFO) cores coated with piezoelectric barium titanate (BTO) shells. CFO-BTO core-shell MENPs have a relatively high magnetoelectric coefficient and have been proposed for direct magnetic particle imaging (MPI) of brain electrophysiology. However, the feasibility of acquiring such readouts has not been demonstrated or methodically quantified. Here we present the results of implementing a strain-based finite element magnetoelectric model of CFO-BTO core-shell MENPs and apply the model to quantify magnetization in response to neural electric fields. We use the model to determine optimal MENPs-mediated electrophysiological readouts both at the single neuron level and for MENPs diffusing in bulk neural tissue for in vivo scenarios. Our results lay the groundwork for MENP recording of electrophysiological signals and provide a broad analytical infrastructure to validate MENPs for biomedical applications.

Versatile Strategy for Electrophoretic Deposition of Polyvinylidene Fluoride-Metal Oxide Nanocomposites

Polyvinylidene fluoride (PVDF) is an advanced functional polymer which exhibits excellent chemical and thermal stability, and good mechanical, piezoelectric and ferroelectic properties. This work opens a new strategy for the fabrication of nanocomposites, combining the functional properties of PVDF and advanced inorganic nanomaterials. Electrophoretic deposition (EPD) has been developed for the fabrication of films containing PVDF and nanoparticles of TiO₂, MnO₂ and NiFe₂O₄. An important finding was the feasibility of EPD of electrically neutral PVDF and inorganic nanoparticles using caffeic acid (CA) and catechol violet (CV) as co-dispersants. The experiments revealed strong adsorption of CA and CV on PVDF and inorganic nanoparticles, which involved different mechanisms and facilitated particle dispersion, charging and deposition. The analysis of the deposition yield data, chemical structure of the dispersants and the microstructure and composition of the films provided an insight into the adsorption and dispersion mechanisms and the influence of deposition conditions on the deposition rate, film microstructure and composition. PVDF films provided the corrosion protection of stainless steel. Overcoming the limitations of other techniques, this investigation demonstrates a conceptually new approach for the fabrication of PVDF-NiFe₂O₄ films, which showed superparamagnetic properties. The approach developed in this investigation offers versatile strategies for the EPD of advanced organic-inorganic nanocomposites.

Design of Ionic-Liquid-Based Hybrid Polymer Materials with a Magnetoactive and Electroactive Multifunctional Response

Multifunctional materials with sensor and actuator capabilities play an increasing role in modern technology. In this scope, hybrid materials with magnetic sensing and an electromechanical actuator response based on magnetic ionic liquids (MILs) and the polymer poly(vinylidene fluoride) (PVDF) have been developed. MILs comprising different cation alkyl chain lengths [C_nmim]⁺ and sharing the same anion [FeCl₄]^- were incorporated at 20 wt % into the PVDF matrix and the morphological, physical, chemical, and functional properties of the materials were evaluated. An increasing IL alkyl chain length leads to the formation of a porous structure, together with an increase in the electroactive PVDF β-phase content of the polymer and a decrease in the crystallinity degree and thermal stability. The magnetic susceptibility of the [C_nmim][FeCl₄]/PVDF films reveals a paramagnetic behavior. The multifunctional response is characterized by a magnetoionic response that decreases with increasing IL alkyl chain length, the highest magnetoionic coefficient (1.06 ± 0.015 V cm^-1 Oe^-1) being observed for [C₂mim][FeCl₄]/PVDF. The electromechanical actuator response is characterized by a highest displacement of 1.1 mm for the [C₄mim][FeCl₄]/PVDF film by applying a voltage of 4 V at a frequency of 100 mHz. Further, their solution processing makes these multiresponsive materials compatible with additive manufacturing technologies.

Enhanced magnetoelectric coupling and dielectric constant in flexible ternary composite electrospun fibers of PVDF-HFP loaded with nanoclay and NiFe2O4 nanoparticles

Magnetoelectric flexible composite fiber mats with superior room temperature magnetoelectric properties.

Shielding Effectiveness Study of Barium Hexaferrite-Incorporated, β-Phase-Improved Poly(vinylidene fluoride) Composite Film: A Metamaterial Useful for the Reduction of Electromagnetic Pollution

The present work reports the high electromagnetic interference (EMI) shielding effectiveness of ∼-93.5 dB at 8.63 GHz and -97.6 dB at 8.61 GHz in the X- and K_u-bands for 10 and 20 wt % of barium hexaferrite (BaH) nanoparticle-loaded poly(vinylidene fluoride) (PVDF)-based composite films with a thickness of ∼0.210 and 0.260 mm, respectively. BaH-PVDF composite films with a layer structure have been considered in the present report in order to establish an excellent EMI shielding material for the suppression of electromagnetic pollution, with good control on flexibility, surface area, and thickness. Structural and morphological measurements reveal that the polar β-phase crystallization of the BaH-PVDF composite films has been enhanced in comparison to the pure PVDF film, and these measurements also reveal the influence of BaH nanoparticles on structural alteration from nonpolar α-phase to the polar/electroactive β-phase of the PVDF matrix. The resultant BaH-PVDF composite films produce multiple interfaces between magnetic BaH nanoparticles and β-phase-enriched electroactive PVDF, which plays the most significant role for the enhancement of the EMI shielding effectiveness (SE) in the microwave/GHz frequency range. This high value of the EMI SE with >99.999999999% attenuation has not been found so far in the PVDF-based composite materials by anyone else. This particular feature of BaH-PVDF composite materials suggests that the BaH-PVDF composite films can be considered as the most useful ones for the fabrication of lightweight, flexible, and thickness-controlled EMI shielding materials for the reduction of pollution created by the electromagnetic waves in the microwave/GHz frequency region.

Electrical and room temperature multiferroic properties of polyvinylidene fluoride nanocomposites doped with nickel ferrite nanoparticles

The higher values of magneto-dielectric coupling is observed in flexible multiferroic polyvinylidene fluoride (PVDF) nanocomposites doped with nickel ferrite (NFO) nanoparticles.

S. K, M. S. J, Thomas S, Philip J, Rouxel D, Bhowmik RN, Kalarikkal N. Flexible and self-standing nickel ferrite–PVDF-TrFE cast films: promising candidates for high-end magnetoelectric applications

Polymer-based magnetoelectrics are identified as a newly emerging area of research due to their profound potential applications centered on spintronic technology.

S. K, Jayalakshmy MS, Thomas S, Rouxel D, Philip J, Bhowmik RN, Kalarikkal N. Dopamine functionalization of BaTiO3: an effective strategy for the enhancement of electrical, magnetoelectric and thermal properties of BaTiO3-PVDF-TrFE nanocomposites

Electro-active polymer–ceramic composites are emerging materials in the fields of nano/macro electronic and microelectromechanical device applications.