Magneto-piezoresistivity in iron particle-filled silicone: An alternative outlook for reading magnetic field intensity and direction

Abstract

Abstract. Elastomagnetic effect (strain induced by magnetic field application) and piezoresistivity (change of electron conductivity due to an induced strain) are coupled in composite materials constituted by magnetic and conductive microparticles into an elastic matrix. On the basis of these effects, the principle of a new method to read magnetization direction changes, in a random sequence, is proposed and experimentally demonstrated. We have produced new composite magnetopiezoresistive samples, constituted of thin chip shaped Fe microparticles inside a silicone matrix, which under an applied magnetic field along their longitudinal axis, undergo an induced strain depending on the local magnetization direction. The resulting resistivity change can be easily detected and used to deduce the local magnetization direction. The magnetization and strain processes are reversible so that after the removal of external magnetizing field the sample is ready for new measurements. A demonstrator prototype has been conceived, produced and tested. The experimental results provide interesting data encouraging to continue the research towards nano-scale devices in order to pursue the intriguing perspective to achieve a magnetic field gradient sensitivity able to reveal magnetization of semipermanent nanomagnets, polarized 'up' and 'down'.

Elastomagnetic nanofiber wires by magnetic field assisted electrospinning

“…The proof of the NPs magnetic moment preferential orientation within the magnetic electrospun nanofibers wire (MENW) can be obtained by comparing the longitudinal magnetization cycle with respect to the transverse one. In our case, a preferential orientation of the main geometric axis of the NPs should not be high because the Ni MNPs have low shape anisotropy (pseudo-spherical shape [33,42]). Taking this into account, Figure 5 clearly shows that longitudinal magnetization (black curve) is slightly easier than the transverse one (red curve).…”

“…Undoubtedly, the implementation of the MFAE technique reported in this work allowed to put together the peculiar properties of the obtained sample: good elasticity of the PCU matrix; high density of the incorporated magnetic nanoparticles; wire-shaped nanofiber systems; preferential longitudinal magnetization. Just the coupling of these properties is the prerequisite for providing a very high direct elastomagnetic effect: a great strain produced by magnetization [42]. To verify this expectation, the new MENWs were subjected to two fundamental tests: evaluation of longitudinal strain induced by longitudinal magnetization -in a horizontal plane -in the case of a sample clamped at an end (Figures 7a and 7b); determination of the deflection produced by a transverse magnetizing field in a horizontal plane, when a MENW is bound at both the ends (Figure 7c).…”

Electro-Active Polymers (EAPs): A Promising Route to Design Bio-Organic/Bioinspired Platforms with on Demand Functionalities

“…The progressive discovery of materials with new chemical functionalities ( i.e. , magnetic [ 115 ], optical [ 116 ], piezo [ 117 ], magnetopiezo [ 118 ]) is running towards the development of novel drug delivery systems able to face new application fields ( i.e. , diagnostic, teranostic), which were previously unsuited to traditional delivery systems.…”

Comparative analysis of electrospun PNIPAAm blends with some biodegradable polymers

“…In some polymers, alteration of a property such as color, conformation, solubility, etc., may be a response to being subjected to certain external stimuli, which may include, among others, temperature [8,31], light [32,33], electric or magnetic fields [17,34], and pH [31,35]. Such polymers are called smart polymers and they can be applied in many areas, for example, in filtration [36,37], cell growth/detachment [38,39], and sensors [33,40], as well as those already mentioned above (drug delivery, tissue engineering scaffolds, wound dressing, and biomedicine).…”