Graphene Origami with Highly Tunable Coefficient of Thermal Expansion

The
coefficient of thermal expansion, which measures the change
in length, area, or volume of a material upon heating, is a fundamental
parameter with great relevance for many applications. Although there
are various routes to design materials with targeted coefficient of
thermal expansion at the macroscale, no approaches exist to achieve
a wide range of values in graphene-based structures. Here, we use
molecular dynamics simulations to show that graphene origami structures
obtained through pattern-based surface functionalization provide tunable
coefficients of thermal expansion from large negative to large positive.
We show that the mechanisms giving rise to this property are exclusive
to graphene origami structures, emerging from a combination of surface
functionalization, large out-of-plane thermal fluctuations, and the
three-dimensional geometry of origami structures.