Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA.
Nat Mater. 2013 Apr;12(4):321-5. doi: 10.1038/nmat3542. Epub 2013 Jan 20.
Crumpled graphene films are widely used, for instance in electronics, energy storage, composites and biomedicine. Although it is known that the degree of crumpling affects graphene's properties and the performance of graphene-based devices and materials, the controlled folding and unfolding of crumpled graphene films has not been demonstrated. Here we report an approach to reversibly control the crumpling and unfolding of large-area graphene sheets. We show with experiments, atomistic simulations and theory that, by harnessing the mechanical instabilities of graphene adhered on a biaxially pre-stretched polymer substrate and by controlling the relaxation of the pre-strains in a particular order, graphene films can be crumpled into tailored self-organized hierarchical structures that mimic superhydrophobic leaves. The approach enables us to fabricate large-area conductive coatings and electrodes showing superhydrophobicity, high transparency, and tunable wettability and transmittance. We also demonstrate that crumpled graphene-polymer laminates can be used as artificial-muscle actuators.
褶皱石墨烯薄膜被广泛应用于电子、储能、复合材料和生物医学等领域。虽然人们已经知道褶皱的程度会影响石墨烯的性质以及基于石墨烯的器件和材料的性能，但褶皱石墨烯薄膜的可控折叠和展开尚未得到证明。在这里，我们报告了一种可实现大面积石墨烯片可控折叠和展开的方法。我们通过实验、原子模拟和理论证明，通过利用粘附在双轴预拉伸聚合物基底上的石墨烯的力学不稳定性，并以特定的顺序控制预应变的松弛，石墨烯薄膜可以被折叠成具有自组织分层结构的褶皱，这种结构可以模拟超疏水叶子。该方法使我们能够制造出大面积的导电涂层和电极，这些涂层和电极具有超疏水性、高透明度以及可调节的润湿性和透光率。我们还证明了褶皱石墨烯-聚合物层压板可用作人工肌肉致动器。
