This proposal describes a plan for combined experimental and theoretical efforts to expand the understanding of mechanical properties and electronic structure of graphene and other two-dimensional materials under ultrahigh strain. This proposal builds upon recent work published in Science by two of the PIs, in which unprecedentedly large elastic strains of approximately 25% were obtained prior to failure. The proposed work includes three experimental thrusts that build on these results. First, the directionally-dependent nonlinear mechanical properties of graphene will be measured up to ultrahigh strains by performing nanoindentation tests of graphene nanoribbons with known lattice orientation. Second, these techniques will be carried over to other two-dimensional materials. Third, the electronic properties of these materials will be studied under ultrahigh strain. A crosscutting theoretical thrust will explore the ability of ab-initio theory to predict these results, and the ab-initio results will be used to parameterize a continuum model.
Ultrahigh strain strain states are both a scientific and technological frontier. Given the many potential applications for which graphene is being studied, ranging from space elevators to electronic circuits, the results from this study will likely have widespread applications. Furthermore, the simplicity of these two-dimensional materials makes them a prime testbed for multi-scale modeling, ranging from the atomic level to the continuum. This work will sponsor two graduate students, who will learn a broad range of skills, including nanofabrication, nanomaterials synthesis, nanomechanical testing, and theory. In addition, the work is highly accessible to undergraduate and high school students: the PIs will support two undergraduates during the period of the grant, and at least one high school student. Finally, the PIs will develop simulations and animations to build a teaching module on the NanoEd resource portal maintained by the National Center for Learning and Teaching in Nanoscale Science and Engineering.
