Mangum James M, Harerimana Ferdinand, Gikunda Millicent N, Thibado Paul M
Department of Physics, University of Arkansas, Fayetteville, AR 72701, USA.
Membranes (Basel). 2021 Jul 9;11(7):516. doi: 10.3390/membranes11070516.
Electrically conductive, highly flexible graphene membranes hold great promise for harvesting energy from ambient vibrations. For this study, we built numerous three-dimensional graphene ripples, with each featuring a different amount of compression, and performed molecular dynamics simulations at elevated temperatures. These ripples have a convex cosine shape, then spontaneously invert their curvature to concave. The average time between inversion events increases with compression. We use this to determine how the energy barrier height depends on strain. A typical convex-to-concave curvature inversion process begins when the ripple's maximum shifts sideways from the normal central position toward the fixed outer edge. The ripple's maximum does not simply move downward toward its concave position. When the ripple's maximum moves toward the outer edge, the opposite side of the ripple is pulled inward and downward, and it passes through the fixed outer edge first. The ripple's maximum then quickly flips to the opposite side via snap-through buckling. This trajectory, along with local bond flexing, significantly lowers the energy barrier for inversion. The large-scale coherent movement of ripple atoms during curvature inversion is unique to two-dimensional materials. We demonstrate how this motion can induce an electrical current in a nearby circuit.
具有导电性且高度灵活的石墨烯膜在从环境振动中收集能量方面具有巨大潜力。在本研究中，我们构建了众多三维石墨烯波纹，每个波纹具有不同程度的压缩，并在高温下进行了分子动力学模拟。这些波纹呈凸余弦形状，然后会自发地将其曲率反转成凹形。反转事件之间的平均时间随压缩程度增加。我们利用这一点来确定能垒高度如何依赖于应变。典型的从凸到凹的曲率反转过程始于波纹的最大值从正常中心位置侧向移向固定的外边缘。波纹的最大值并非简单地向下移向其凹形位置。当波纹的最大值移向外边缘时，波纹的另一侧被向内和向下拉动，并且它首先穿过固定的外边缘。然后，波纹的最大值通过快速屈曲迅速翻转到另一侧。这条轨迹，连同局部键的弯曲，显著降低了反转的能垒。在曲率反转过程中，波纹原子的大规模协同运动是二维材料所特有的。我们展示了这种运动如何在附近电路中感应出电流。
