Soutik Betal

BaTiO3 Coated CoFe2O4–Core-Shell Magnetoelectric Nanoparticles (CSMEN) Characterization

Multiferroic behavior of magnetoelectric nanoparticles exhibiting both ferromagnetic and ferroelectric properties find significance in various applications. In this study, core-shell magnetoelectric nanoparticles (CSMEN) have been fabricated by coating CoFe2O4 nanoparticles with BaTiO3 by weight using hydro-thermal method. The core-shell structure was confirmed by electron microscopy and topographic scanning probe microscopic measurements were performed for further structural analysis. While magnetic force microscopy and ferromagnetic hysteresis loop measurements substantiated ferromagnetic behavior of the core, piezo response force microscopy confirmed ferroelectric behavior and single crystalline nature of BaTiO3 shell. As analyzed by TEM diffraction pattern both core and shell are in cubic phase with their respective diffraction spots depicting their single crystalline nature.

Magneto-elasto-electroporation (MEEP): In-vitro visualization and numerical characteristics

A magnetically controlled elastically driven electroporation phenomenon, or magneto-elasto-electroporation (MEEP), is discovered while studying the interactions between core-shell magnetoelectric nanoparticles (CSMEN) and biological cells in the presence of an a.c. magnetic field. In this paper we report the effect of MEEP observed via a series of in-vitro experiments using core (CoFe2O4)-shell (BaTiO3) structured magnetoelectric nanoparticles and human epithelial cells (HEP2). The cell electroporation phenomenon and its correlation with the magnetic field modulated CSMEN are described in detail. The potential application of CSMEN in electroporation is confirmed by analyzing crystallographic phases, multiferroic properties of the fabricated CSMEN, influences of d.c. and a.c. magnetic fields on the CSMEN and cytotoxicity tests. The mathematical formalism to quantitatively describe the phenomena is also reported. The reported findings provide insights into the underlying MEEP mechanism and demonstrate the utility of CSMEN as an electric pulse-generating nano-probe in electroporation experiments with a potential application toward accurate and efficient targeted cell permeation.

Thermal effects in magnetoelectric properties of NiFe2O4/Pb(Zr0.52Ti0.48)O3/NiFe2O4 tri-layered composite

ABSTRACT Layered composite electro-ceramics can be designed to exhibit the magnetoelectric (ME) effect based on stress transfer from magnetostriction of ferromagnetic layer to the ferroelectric layer. Many studies in search of giant ME coefficients in layered composites have been made but there are less studies regarding the ME effect in these ceramic materials as a function of temperature, mainly at low temperatures. With the influential increase in magnetoelectric sensing devices use in extreme, minute or precise field monitoring, a broadband temperature dependent analysis on ME effect of these sensors is much required. In this work the effect of temperature on ME effect in a NiFe2O4/Pb(Zr0.52Ti0.48)O3/NiFe2O4 layered composite are studied and any major/minute change have been analyzed. Dynamic ME measurements shows a maximum linear ME coefficient (αME = 238 mV/cm.Oe) by applying an AC magnetic field in a frequency of 600 Hz at room. Highly reduced αME values are observed at low temperatures. Magnetocapacitance effect studies showed a strong magnetoelectric coupling at room temperature and, also, a dramatic reduction in the magnetoelectric coupling at 200 K and 100 K. Analyzing the phenomena mathematically shows that there is a secondary effect interaction which influences the ME effect intensity depending on temperature.

Core-shell magnetoelectric nanorobot – A remotely controlled probe for targeted cell manipulation

We have developed a remotely controlled dynamic process of manipulating targeted biological live cells using fabricated core-shell nanocomposites, which comprises of single crystalline ferromagnetic cores (CoFe2O4) coated with crystalline ferroelectric thin film shells (BaTiO3). We demonstrate them as a unique family of inorganic magnetoelectric nanorobots (MENRs), controlled remotely by applied a.c. or d.c. magnetic fields, to perform cell targeting, permeation, and transport. Under a.c. magnetic field excitation (50 Oe, 60 Hz), the MENR acts as a localized electric periodic pulse generator and can permeate a series of misaligned cells, while aligning them to an equipotential mono-array by inducing inter-cellular signaling. Under a.c. magnetic field (40 Oe, 30 Hz) excitation, MENRs can be dynamically driven to a targeted cell, avoiding untargeted cells in the path, irrespective of cell density. D.C. magnetic field (−50 Oe) excitation causes the MENRs to act as thrust generator and exerts motion in a group of cells.

Low frequency piezoresonance defined dynamic control of terahertz wave propagation.

Phase modulators are one of the key components of many applications in electromagnetic and opto-electric wave propagations. Phase-shifters play an integral role in communications, imaging and in coherent material excitations. In order to realize the terahertz (THz) electromagnetic spectrum as a fully-functional bandwidth, the development of a family of efficient THz phase modulators is needed. Although there have been quite a few attempts to implement THz phase modulators based on quantum-well structures, liquid crystals, or meta-materials, significantly improved sensitivity and dynamic control for phase modulation, as we believe can be enabled by piezoelectric-resonance devices, is yet to be investigated. In this article we provide an experimental demonstration of phase modulation of THz beam by operating a ferroelectric single crystal LiNbO3 film device at the piezo-resonance. The piezo-resonance, excited by an external a.c. electric field, develops a coupling between electromagnetic and lattice-wave and this coupling governs the wave propagation of the incident THz beam by modulating its phase transfer function. We report the understanding developed in this work can facilitate the design and fabrication of a family of resonance-defined highly sensitive and extremely low energy sub-millimeter wave sensors and modulators.

Photoacoustic and magnetoelastic property of cobalt ferrite nanoparticles and its attenuation with barium titanate coating

We report an experimental study, where Cobalt Ferrite (CoFe2O4) nanoparticles exhibit Photoacoustic (PA) emission peak intensity of 235.2V/J when analyzed under the Opto-Acoustic measurement setup. PA emission peak intensity decreases to 210V/J when AC Magnetic field is applied and further when Barium Titanate coated cobalt ferrite nanoparticles were analyzed, the PA peak further reduces to 68.76667V/J and with application of AC magnetic field the peak completely disappears. The measurement depicts the Photoacoustic and magnetoelastic behavior of cobalt ferrite nanoparticles.

Achieving magneto-elasto-electroporation and cell transport using core-shell magnetoelectric nanoparticles(Conference Presentation)

Magneto-Elasto-Electroporation (MEEP) is a magnetically controlled acoustic-electroporation observed while core-shell Magneto-electric nanoparticles interact with Biological Cells. The surface polarity change of the piezoelectric coating (BaTiO3) due to absorption of pressure created due magneto-striction of core (CoFe2O4) in AC magnetic field results in electric field (Uext) change at the external vicinity of the cell membrane when nanoparticles are nearby. This results in transmembrane Voltage (Um) change which is basically the difference in Cell’s internal potential (Uint) and external potential. The nonlinear permeability change of cell membrane due to change in Um opens the nano-pores on the membrane. The magnetic moment of the nanoparticles further helps in penetration of the Magneto-electric nanoparticles inside the cell through these magneto-electrically controlled newly opened nano-pores on cell’s membrane. MEEP is analyzed through in-vitro analysis and Mathematical equations are formulated for numerically expressing its fundamental effect. TEM imaging, XRD analysis, Zeta-potentiometer measurement and AFM imaging are confirming the coating of the piezoelectric layer on Magneto-stricitve nanoparticles, Acoustic measurements confirms the photo-acoustic and magneto-acoustic property of CoFe2O4 nanoparticles and Fluorescence microscopy as well as Confocal microscopy are confirming the penetration of particle inside the Human Epithelial cells (HEP2). Further on application of repulsive magnetic field, nanoparticles are observed to transport a group of cells in controlled boundary conditions in microfluidic chamber. Hence these nanoparticles can be used for accurate and efficient drug delivery as well as cell transport applications

Cell permeation using core-shell magnetoelectric nanoparticles

ABSTRACT Nano-electroporation on biological cell membrane using core shell magnetoelectric nanoparticles (CSMEN) has been discussed in this paper. Pulsed electric field created by the CSMEN in presence of a.c. magnetic field interacts with the polar phosphate heads of the phospholipid bilayer membrane when they are sub-micron distance apart. This interaction primarily results in electrostatic repulsion between the negative phosphate heads and negative pulse electric field created by core-shell magnetoelectric nanoparticles. The repulsion forces the phospholipids to dislocate from their position resulting in opening of volcano shape nanopore on the cell membrane. This study will broadly demonstrate the potential of CSMEN for application as nano-probe or fluorescent dye marked probes for electroporation experiments and for the ultimate goal of achieving efficiently targeted drug delivery applications.

Control of crystalline characteristics of shell in core-shell magnetoelectric nanoparticles studied using HRTEM and holography

ABSTRACT Magnetoelectric layered composites can be designed to exhibit the magnetoelectric effect based on transfer of stress from magnetostriction of ferromagnetic layer to the ferroelectric layer. In this study Core-Shell magnetoelectric nanoparticles (CSMEN) have been fabricated by coating BaTiO3 on CoFe2O4 nanoparticles (∼50nm) by molar mass ratio using hydro-thermal method. The control factor in the fabrication process is the use of different shape and morphology of the CoFe2O4 core. The crystallinity of the barium titanate (BT) coating changes from single crystalline to polycrystalline nature depending on the BT coating thickness. The BT shell thickness during CSMEN fabrication largely varies with the morphology of the substrate which is the cobalt ferrite nanoparticle. The shape, size and coagulation are the morphological characteristics of cobalt ferrite nanoparticles which plays major role for single crystalline BT coating on it. The bigger the size or the uneven surface morphology/shape of cobalt ferrite nanoparticles, the bigger (polycrystalline) BT shells formation by the same process of fabrication. The process of coating of BT shell on cobalt ferrite nanoparticles is analyzed step by step to accurately measure the maximum thickness of shell to sustain single crystallinity. The maximum size of BT coating prepared by this method to sustain single crystallinity is up to 41.2 nm which is approximately ∼100 unit cells of barium titanate. High resolution transmission electron microscopy (HRTEM), selected area electron diffraction pattern (SAED) and holography have been used in this study to visualize and characterize the integrated morphology of CSMEN.