Center for Mechanics of Solids, Structures and Materials

Mechanics of Graphene and Interfaces

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Research Objectives

The primary objectives of this project are: (1) Develop experimental techniques for characterizing the adhesive interactions between graphene and supporting substrates at the nano and meso scales; (2) Develop physics-based, experimentally calibrated theoretical models and numerical simulations of graphene interacting with surrounding materials; (3) Explore new mechanistic approaches to mechanistically produce large-area graphene films.

Principal Investigators

Kenneth M. Liechti, Rui Huang, Rodney S. Ruoff

Highlights

ripple1 Thermal rippling of graphene
Thermomechanical properties of monolayer graphene with thermal rippling are studied by both statistical mechanics analysis and molecular dynamics (MD) simulations. The amplitude of thermal rippling is found to depend on the membrane size by a power law with different exponents under zero stress and zero strain conditions. Such thermal rippling is responsible for the effectively negative in-plane thermal expansion of graphene at relatively low temperatures, while a transition to positive thermal expansion is predicted as the anharmonic interactions suppress the rippling effect at high temperatures. Moreover, subject to equi-biaxial tension, the in-plane stress-strain relation of graphene becomes nonlinear even at infinitesimal strain, and the tangent biaxial modulus of graphene depends on strain non-monotonically and decreases with increasing temperature.

blister2 A blister test for interfacial adhesion of graphene
Chemical vapor deposition (CVD) grown graphene had been transferred to a highly polished copper substrate from its seed foil. The graphene/photoresist composite film was pressurized with deionized water through a nominally 1-mm hole in the copper and the deflection of the membrane was measured by a full field interference method. The deflection profiles compared well with those obtained from a linear plate model that accounted for the initial strain in the membrane and a relaxed boundary condition at the edge of the blister. This was used to calculate the energy release rate as a function of delamination growth to obtain fracture resistance curves for the graphene/copper interface. The measured adhesion energy for the graphene/copper interface was higher than that of a photoresist/copper interface, but slightly lower than previous measurements for as-grown graphene on copper foil.

Selected Publications