Influence of liquid substrates on the mechanics of single-layer graphene*

Emerging 2D materials are excellent candidates for next generation technologies such as supercapacitors, filtration membranes and flexible solar cells. In particular, the price of production of high quality graphene, a 2D carbon honeycomb lattice, plummeted over the past decade. Only an atom thin, graphene does not obey the laws of continuum mechanics. A striking example is that electron-electron repulsion pilots the bending stiffness at zero temperature, not the elasticity of the atomic bonds.

The wrinkling of a floating graphene sheet under compression show that adsorption of liquid molecules dramatically disrupts graphene mechanics, yielding new records of flexibility at 0.02 kT. The addition of alcohols also promotes spontaneous wrinkling, even without compression. The mismatch in C-C bond length in graphene and alcohol produces a spontaneous curvature of the graphene sheet, under an ``atomic pinchers'' scenario. We characterize this new adsorption-induced wrinkling transition by coupled optical microscopy and Raman spectroscopy.
Our results open possibilities of simple methods to tune the equilibrium mechanics and geometry of large scale graphene-based devices.