介电弹性体中的机电滞回和共存态

人们正在开发活性聚合物来模拟生命的一个显著特征:对刺激做出反应的运动。大变形会导致有趣的现象;例如，最近的实验表明，电压可以使介电弹性体的一层变形为两种共存的状态，一种是扁平的，另一种是褶皱的。这一观察结果，以及在不同刺激下分析大变形的需要，使我们重新审视了电力学理论。在他的经典著作中，麦克斯韦证明了真空中导体之间的电力可以用真空中的应力场来计算。麦克斯韦应力后来被应用于可变形介质中。这种做法的理论基础并不牢固。费曼指出，区分材料内部的电力和机械力是一个尚未解决的问题，可能是不必要的。最近，电力学理论被重新表述，绕过了麦克斯韦应力的概念。本文进一步发展了机电失稳理论。 We show that the free energy of a typical dielectric elastomer is non-convex, such that homogenous deformation in a layer can become unstable and give way to coexistent states of two thicknesses. A region of the thin state has a large area, and wrinkles when constrained by nearby regions of the thick state. If the voltage is controlled to ramp, the elastomer may exhibit hysteresis, much like a ferroelectric. If the charge is controlled to ramp, the two states may coexist at a constant voltage, while the new state may grow at the expense of the old. The net flow of charge associated with the transition can be tuned, along with other characteristics of the coexistent states, by the degree of crosslink and the state of stress.