Multiscale theory, mechanisms, and designs for giant flexoelectricity of elastomers

Soft materials which can undergo large deformations and exhibit a strong coupling between strain-gradient and polarization would have wide ranging applications in nanotechnologies, wearable sensors and electronics, soft robotics, and energy harvesting. This coupling--namely, the flexoelectric effect--is a universal phenomenon. While flexoelectricity is well understood for crystalline materials, the molecular-scale theoretical underpinnings of flexoelectricity in elastomers is lacking. In this talk, using statistical mechanics and network theory, we develop a multiscale constitutive model of elastomers consisting of polar monomers. This not only allows us to explain the flexoelectric effect across scales; it also agrees with a poorly understood, but experimentally validated, mechanism for achieving giant flexoelectricity in elastomers: combining stretching with bending. We conclude by discussing how polymer network architectures may be designed to tune the flexoelectric effect in different directions relative to the strain-gradient. This work contributes to our theoretical understanding and has important implications towards achieving high-fidelity soft sensors, energy harvesters, and soft robots with many degrees-of-freedom mechanisms.