Multiscale Graphene Topographies Programmed By Sequential Mechanical Deformation

Multiscale Graphene Topographies Programmed by Sequential Mechanical Deformation

Po-Yen Chen^1,2*, Robert H. Hurt², Ian Y. Wong²

¹Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139

²School of Engineering, Brown University, Providence, RI 02912

Email: pychen@mit.edu

 

            Complex surface topographies emerge in ultrathin-layered materials undergoing large mechanical deformations. Yet, the ability to independently engineer feature size and orientational order across multiple length scales remains a challenge. In this study, we demonstrate hierarchical graphene surface architectures generated using various sequences and combinations of extreme mechanical deformation. The method involves multiple cycles of compression driven by thermal actuation of pre-stretched polymer substrates followed by polymer dissolution, graphene film transfer, and recompression. In each generation, the compression can be biaxial (2D) or unidirectional (1D), and the 1D contraction step can be aligned parallel or perpendicular to the previous step, leading to a family of different hierarchical wrinkle/crumple textures (Figure 1, the scale bars are 4 micrometers). Analysis of the three-generational genealogy of these graphene films shows that both directionality and sequence play a role in final texture, and that the characteristic length scale of the features increases with subsequent generations. This behavior can be explained through the increase in effective film thickness (which is directly related to feature size) as complex, out-of-plane textures are added in each successive generation. These films show systematic increases in hydrophobicity and electrochemical current density with each successive generation, and the final product of three-generational extreme compression shows superhydrophobicity (static contact angle >160 degree) and high electrochemical activity (20-fold increase in comparison with planar GO film). We believe this texturing concept can be extended to other 2D material films and has potential applications in anti-fouling substrates, stretchable electronics and advanced electrode architectures.

Figure 1. The genealogy of GO multigenerational structures from planar generation 0 (G₀) coatings to multiscale generation three (G₃) structures. A₀ indicates the area of initial planar film; A is the area of multigenerational GO film. All of the scale bars are 4 micrometers.