In this work, the dependence of effective Young's modulus on the thickness of suspended graphene was confirmed through a drop impingement method. Large area suspended graphene (LSG) layers with a diameter of up to 400 μm and a nanometer thickness were prepared through transferring chemical vapor deposition grown graphene from copper substrates. 4, 8, and 12-layer LSG samples were found to be crumpled yet defect-free. The mechanical properties of LSG were first studied by observing its interaction with impinging droplets from an ink-jet nozzle. First, the effective Young's modulus was calculated by fitting the instant deformation captured by high speed photography within microseconds. Next, droplets deposited on LSG caused deformation and generated wrinkles and the effective Young's modulus was calculated from the number of wrinkles. The above methods yielded effective Young's modulus values ranging from 0.3 to 3.4 TPa. The results from these methods all indicated that the effective Young's modulus increases with the decreasing thickness or size of suspended graphene layers. Moreover, the crumpled LSG yields higher effective Young's modulus than ideal flat graphene. These comprehensive results from complementary methodologies with precise LSG thickness control down to the nanometer scale provide good evidence to resolve the debate on the thickness dependence of mechanical strength for LSG.

中文翻译：

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通过微滴撞击大面积悬浮石墨烯探索纳米厚弹性薄膜的机械性能

在这项工作中，有效杨氏模量对悬浮石墨烯厚度的依赖性通过液滴冲击法得到证实。通过从铜基板转移化学气相沉积生长的石墨烯，制备直径高达 400 μm 和纳米厚度的大面积悬浮石墨烯 (LSG) 层。发现 4、8 和 12 层 LSG 样品被弄皱但没有缺陷。LSG 的机械性能首先通过观察其与来自喷墨喷嘴的撞击液滴的相互作用来研究。首先，有效杨氏模量是通过拟合高速摄影在微秒内捕获的瞬时变形来计算的。接下来，沉积在 LSG 上的液滴引起变形并产生皱纹，有效杨氏模量由皱纹数计算。上述方法产生的有效杨氏模量值范围为 0.3 至 3.4 TPa。这些方法的结果都表明，有效杨氏模量随着悬浮石墨烯层的厚度或尺寸的减小而增加。此外，皱缩的 LSG 比理想的扁平石墨烯产生更高的有效杨氏模量。这些来自互补方法的综合结果以及精确的 LSG 厚度控制到纳米级，为解决关于 LSG 机械强度的厚度依赖性的争论提供了很好的证据。皱缩的 LSG 比理想的扁平石墨烯产生更高的有效杨氏模量。这些来自互补方法的综合结果以及精确的 LSG 厚度控制到纳米级，为解决关于 LSG 机械强度的厚度依赖性的争论提供了很好的证据。皱缩的 LSG 比理想的扁平石墨烯产生更高的有效杨氏模量。这些来自互补方法的综合结果以及精确的 LSG 厚度控制到纳米级，为解决关于 LSG 机械强度的厚度依赖性的争论提供了很好的证据。