Magnetoelectric and magnetomechanical interactions in compliant composite materials

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The proposed continuation of the project is based on the preliminary results originating from the current stage 2018-2020. The primary goal is to design, fabricate and characterize compliant magnetoelectric (ME) layered structures comprising a magnetoactive elastomer (MAE) as the magnetostrictive phase and a flexible polymer as the piezolectric phase. The piezoelectric polymer will be either a commercial polyvinylidene fluoride or a polydimethylsiloxane-based microstructured ferroelectric material. The direct ME effect in such composite materials originates from the strain-mediated coupling between magnetostriction and piezoelectricity in constitutive materials. In this context, experimental investigations of deformation of MAE bodies in uniform magnetic fields are of importance. Available theories did not reach the state yet, where fabrication guidelines can be provided in order to design a MAE specimen with the desired magnetodeformation. Hitherto, experimental results on MAE magnetostriction are rather fragmentary, mostly refer to earlier generations of MAEs and are often contradicting. The development of soft MAEs in the running project already led to demonstration of a magnetically induced extensional strain, which can be considered as a record. Systematic investigations of deformations of macroscopic MAE bodies (e.g. cylinders and spheroids) in uniform magnetic fields will be performed in order to obtain the dependences on the sample shape (aspect ratio), material composition and the internal structural arrangement of microparticles. From these experiments, the piezomagnetic coefficient can be derived and the recently predicted large scale deformation (shape morphing) of spherical MAE samples should be observed. In the current project the large Wiedemann twist of a MAE tube was discovered. This effect should be investigated further. The dependences of the Wiedemann twist on the geometrical parameters, material composition and the internal structural arrangement of microparticles will be measured. Obtained data sets for linear and rotational deformations of MAE bodies will be used for comparison with the existing and future theoretical models. Possible applications of obtained results are magnetically controlled linear and torsional actuators, magnetic field sensors, energy harvesting devices etc.