Two- and three-dimensional self-folding of free-standing graphene by liquid evaporation
Two- and three-dimensional self-folding of free-standing graphene by liquid evaporation
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DOI：
10.1039/c8sm00873f
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发表时间：
2018-08-07
期刊：
影响因子：
3.4
通讯作者：
Xu, Baoxing
中科院分区：
文献类型：
--
作者：
Liu, Qingchang;Xu, Baoxing
二维（2-D）原子薄石墨烯比其块状石墨表现出了压倒性的优异性能，但其前所未有的性能的广泛应用和探索需要其几何形态的多样性，超越其固有的平面结构。在这项研究中，我们提出了一种自折叠方法，通过蒸发液体溶液将 2D 平面独立石墨烯转化为 2D 和 3D 折叠结构。这种方法涉及液体的表面能与石墨烯的变形能和范德华能之间的竞争。通过结合石墨烯尺寸和表面润湿性，开发了一种基于能量的理论模型来描述液体蒸发过程中的自折叠过程。通过研究矩形、圆形和三角形三种典型的石墨烯几何形状，提取并举例说明了液体蒸发的临界弹性毛细管长度。液体完全蒸发后，还获得了石墨烯能够通过范德华能量实现稳定折叠图案的临界自折叠长度。同时，进行全尺寸分子动力学 (MD) 模拟，以监测变形能和折叠图案随液体蒸发的演变。模拟结果证明了 2D 折叠球拍状和 3D 折叠锥状图案的形成，并且在能量变化和折叠图案方面与理论预测非常一致。这项工作为通过液体蒸发控制石墨烯和其他二维材料自折叠成复杂结构提供了定量指导。
Two-dimensional (2-D) atomically thin graphene has exhibited overwhelming excellent properties over its bulk counterpart graphite, yet the broad applications and explorations of its unprecedented properties require a diversity of its geometric morphologies, beyond its inherently planar structures. In this study, we present a self-folding approach for converting 2-D planar free-standing graphene to 2-D and 3-D folded structures through the evaporation of its liquid solutions. This approach involves competition between the surface energy of the liquid, and the deformation energy and van der Waals energy of graphene. An energy-based theoretical model is developed to describe the self-folding process during liquid evaporation by incorporating both graphene dimensions and surface wettability. The critical elastocapillary length by liquid evaporation is extracted and exemplified by investigating three typical graphene geometries with rectangular, circular and triangular shapes. After the complete evaporation of the liquid, the critical self-folding length of graphene that can enable a stable folded pattern by van der Waals energy is also obtained. In parallel, full-scale molecular dynamics (MD) simulations are performed to monitor the evolution of deformation energies and folded patterns with liquid evaporation. The simulation results demonstrate the formation of 2-D folded racket-like and 3-D folded cone-like patterns and show remarkable agreement with theoretical predictions in both energy variations and folded patterns. This work offers quantitative guidance for controlling the self-folding of graphene and other 2-D materials into complex structures by liquid evaporation.