(571h) 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.