Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity
Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity
复制标题
DOI：
10.1073/pnas.2102477118
复制
发表时间：
2021-05-25
影响因子：
11.1
通讯作者：
Sharma, Pradeep
中科院分区：
文献类型：
--
作者：
Grasinger, Matthew;Mozaffari, Kosar;Sharma, Pradeep
软机器人需要能够大变形并且能够在外部刺激（例如电场）下致动的材料。能量收集、生物医学设备、柔性电子器件和传感器是由电活性软材料实现的一些其他应用。挠曲电现象是一种诱人的替代方案，指的是当受到应变梯度时电介质中电极化的发展。特别地，挠曲电性提供了高度期望的变形模式（挠曲）和电刺激之间的直接线性耦合。不幸的是，除了一些例外情况，挠曲电效应是相当弱的，相当大的弯曲曲率需要一个可观的机电响应。文献中的大多数实验似乎证实了聚合物中的适度挠曲电性，尽管令人困惑的是，一项奇异的工作在某些特定条件下测量了弹性体中的“巨大”效应。由于缺乏对弹性体中挠曲电性的微观基础和相称理论的理解，目前不可能解释弹性体上相互矛盾的实验结果或寻求可能设计大挠曲电性的途径。在这项工作中，我们提出了一个由极性单体组成的弹性体的新兴挠曲电性的弹性力学理论。该理论被证明是有效的，在广泛的普遍性，并导致两个巨人flexoelectricity和材料设计的关键见解。特别地，该理论表明，在标准弹性体网络中，结合拉伸和弯曲是获得巨大挠曲电性的机制，这也解释了上述令人惊讶的实验结果。
Soft robotics requires materials that are capable of large deformation and amenable to actuation with external stimuli such as electric fields. Energy harvesting, biomedical devices, flexible electronics, and sensors are some other applications enabled by electroactive soft materials. The phenomenon of flexoelectricity is an enticing alternative that refers to the development of electric polarization in dielectrics when subjected to strain gradients. In particular, flexoelectricity offers a direct linear coupling between a highly desirable deformation mode (flexure) and electric stimulus. Unfortunately, barring some exceptions, the flexoelectric effect is quite weak and rather substantial bending curvatures are required for an appreciable electromechanical response. Most experiments in the literature appear to confirm modest flexoelectricity in polymers although perplexingly, a singular work has measured a "giant" effect in elastomers under some specific conditions. Due to the lack of an understanding of the microscopic underpinnings of flexoelectricity in elastomers and a commensurate theory, it is not currently possible to either explain the contradictory experimental results on elastomers or pursue avenues for possible design of large flexoelectricity. In this work, we present a statistical-mechanics theory for the emergent flexoelectricity of elastomers consisting of polar monomers. The theory is shown to be valid in broad generality and leads to key insights regarding both giant flexoelectricity and material design. In particular, the theory shows that, in standard elastomer networks, combining stretching and bending is a mechanism for obtaining giant flexoelectricity, which also explains the aforementioned, surprising experimental