Graphene has exceptionally high in-plane strength, which makes it ideal for various nanomechanical applications. At the same time, its exceptionally low out-of-plane stiffness makes it also flimsy and hard to handle, rendering out-of-plane structures unstable and difficult to fabricate. Therefore, from an application point of view, a method to stiffen graphene would be highly beneficial. Here we demonstrate that graphene can be significantly stiffened by using a laser writing technique called optical forging. We fabricate suspended graphene membranes and use optical forging to create stable corrugations. Nanoindentation experiments show that the corrugations increase graphene bending stiffness up to 0.8 MeV, five orders of magnitude larger than pristine graphene and corresponding to some 35 layers of bulk graphite. Simulations demonstrate that, in addition to stiffening by micron-scale corrugations, optical forging stiffens graphene also at the nanoscale. This magnitude of stiffening of an atomically thin membrane will open avenues for a plethora of new applications, such as GHz resonators and 3D scaffolds.

石墨烯具有极高的面内强度，使其非常适合各种纳米机械应用。同时，其极低的平面外刚度也使其脆弱且难以处理，从而使平面外结构不稳定且难以制造。因此，从应用的观点来看，一种使石墨烯变硬的方法将是非常有益的。在这里，我们证明通过使用称为光学锻造的激光写入技术，石墨烯可以显着硬化。我们制造悬浮的石墨烯膜，并使用光学锻造来产生稳定的波纹。纳米压痕实验表明，波纹将石墨烯的弯曲刚度提高到0.8 MeV，比原始石墨烯大五个数量级，并对应于约35层的块状石墨。模拟表明，除了通过微米级的波纹进行硬化以外，光学锻造还在纳米级上使石墨烯硬化。原子薄膜的这种硬化程度将为众多新应用（例如GHz谐振器和3D支架）开辟道路。