Magnetic and ionic liquid inclusions in soft materials and engineering enhanced electro-magneto-mechanical response

Abstract

Magnetoelectric soft materials that polarize in the existence of external magnetic field and magnetize in response to an applied electric voltage have several promising technological applications. However, finding the suitable candidate for device fabrication has been a challenging task. Previous experiments and numerical modeling suggested an enhanced electrostrictive properties for soft materials composites made by depositing high permittivity liquid inclusions. Similarly, it has been reported that small magnetic inclusions significantly improve the magnetostrictive response of a soft composite. In this work, we highlight a simple yet effective mechanism to design soft materials composites with unusually large magnetoelectric coupling, merely by adding minute spherical liquid inclusions. Using a simple homogenization model, we explore the interplay of electrostatics, magnetostatics, soft solids and liquid inclusions on the effective coupling behavior of the soft composite while properly accounting for the capillary effects. This soft composite, which naturally allows large deformations, is also capable of generating electric voltage when subject to an external magnetic field. Meticulous selection of the size of liquid or solid inclusions, volume fraction and matrix materials properties significantly impacts the magnetoelectric coupling coefficient of the soft composite. In particular, choosing ferrofluids improves magnetoelectric response by 134% or higher. Moreover, in the absence of an electric field, a stronger magnetostrictive effect is revealed by ionic liquid inclusions compared to stiff ones, even in the presence of an applied mechanical strain.