Harnessing wrinkling morphologies of graphene on soft substrates for mechanically programmable interfacial thermal conductance

Strain engineering has been leveraged to tune the thermal properties of materials by introducing stress and manipulating local atomic vibrations, which poses a detrimental threat to the mechanical integrity of materials and structures and limits the capability to regulate thermal transport. Here, we report that the interfacial thermal conductance of graphene on a soft substrate can be regulated by harnessing wrinkling and folding morphologies of graphene, which could be well controlled by managing the pre-strain applied to the substrate. These obtained graphene structures are free of significant in-plane mechanical strain and only have infinitesimal distortion to the intrinsic thermal properties of graphene. The subsequent thermal transport studies with pump-probe non-equilibrium molecular dynamics (MD) simulation show that the thermal conductance between graphene structures and the substrate is uniquely determined by the morphological features of graphene. The atomic density of interfacial interactions, energy dissipation, and temperature distribution are elucidated to understand the thermal transport across each graphene structure and substrate. We further demonstrate that the normalized thermal conductance decreases monotonically with the increase of the equivalent mechanical strain, showing the capability of mechanically programmable interfacial thermal conductance in a broad range of strains. Application demonstrations in search of on-demand thermal conductance are conducted by controlling the geometric morphologies of graphene. This study lays a foundation for regulating interfacial thermal conductance through mechanical loading-induced geometric deformation of materials on a soft substrate, potentially useful in the design of flexible and stretchable structures and devices with tunable thermal management performance.