Using electrets to design concurrent magnetoelectricity and piezoelectricity in soft materials

Abstract

Piezoelectricity and magnetoelectricity are contradictory properties with a rather limited set of natural (often hard) materials that exhibit both. Composite materials -almost always restricted to hard ones -provide a limited recourse with the attendant limitations of small strains, fabrication challenges among others. In this article, using the concept of electrets, we propose a simple scheme to design soft, highly deformable materials that simultaneously exhibit piezoelectricity and magnetoelectricity. We demonstrate that merely by embedding charges and ensuring elastic heterogeneity, the geometrically nonlinear behavior of soft materials leads to an emergent piezoelectric and magnetoelectric behavior. We find that an electret configuration made of sufficiently soft (nonpiezoelectric and nonmagnetic) polymer foams can exhibit simultaneous magnetoelectricity and piezoelectricity with large coupling constants that exceed the best-known ceramic composites. Moreover, we show that these properties can be tuned with the action of an external field.

2D Electrets of Ultrathin MoO2 with Apparent Piezoelectricity

“…[ 36 ] Recent theoretical modeling has well‐explained the origins of the apparent piezoelectric, flexoelectric, and pyroelectric behavior in electrets (in otherwise nonpiezoelectric) materials due to the interaction of Maxwell stress (or electrostriction), deformation nonlinearity, and the presence of the charges or dipoles. [ 37–41 ]…”

“…[36] Recent theoretical modeling has well-explained the origins of the apparent piezoelectric, flexoelectric, and pyroelectric behavior in electrets (in otherwise nonpiezoelectric) materials due to the interaction of Maxwell stress (or electrostriction), deformation nonlinearity, and the presence of the charges or dipoles. [37][38][39][40][41] To date, although electrets have been demonstrated for soft polymer foams, there is no example of a 2D electret material. In particular, a key aspect of electret is that charges must be stabilized since the electret state is metastable and the charges have a tendency to decay.…”

Diversifying temporal responses of magnetoactive elastomers

“…where the last term is a constraint to the incompressible materials , q is the Lagrangian multiplier which can be interpreted as the hydrostatic pressure. We assume that the relative permeability of the free space around the deformed body is equal to 1 and the perturbation field outside V vanishes because of the thin-film geometry (Coey 2011, Alameh et al 2015. The magnetic field and the perturbation field in the current configuration are given by…”

A new type of Maxwell stress in soft materials due to quantum mechanical-elasticity coupling

“…The many clever applications of the Maxwell stress concept in the context of soft multifunctional materials, that range from energy harvesting to soft loud speakers, are well-illustrated recently by the works of (Koh et al, 2011;Zhao et al, 2007Zhao et al, , 2010Li et al, 2013). In particular, Maxwell stress may be combined with the notion of electrets to design novels kinds of apparently piezoelectric materials (Kacprzyk et al, 1995;Paajanen et al, 2000;Bauer et al, 2004;Wegener and Bauer, 2005;Hillenbrand and Sessler, 2008;Deng et al, 2014a,b;Alameh et al, 2015).…”