Shear Rheology Control of Wrinkles and Patterns in Graphene Oxide Films

Abstract

Drying graphene oxide (GO) films are subject to extensive wrinkling, which largely affects their final properties. Wrinkles were shown to be suitable in biotechnological applications; however, they negatively affect the electronic properties of the films. Here, we report on wrinkle tuning and patterning of GO films under stress-controlled conditions during drying. GO flakes assemble at an air-solvent interface; the assembly forms a skin at the surface and may bend due to volume shrinkage while drying. We applied a modification of evaporative lithography to spatially define the evaporative stress field. Wrinkle alignment is achieved over cm areas. The wavelength (i.e., wrinkle spacing) is controlled in the μm range by the film thickness and GO concentration. Furthermore, we propose the use of nanoparticles to control capillary forces to suppress wrinkling. An example of a controlled pattern is given to elucidate the potential of the technique. The results are discussed in terms of classical elasticity theory. Wrinkling is the result of bending of the wet solid skin layer assembled on a highly elastic GO dispersion. Wavelength selection is the result of energy minimization between the bending of the skin and the elastic deformation of the GO supporting dispersion. The results strongly suggest the possibility to tune wrinkles and patterns by simple physicochemical routes.

A Photoaddressable Liquid Crystalline Phase Transition in Graphene Oxide Nanocomposites

“…Increasing the wt% of rGO/brush hybrid forces the platelets to enhance their alignment and minimize the excluded volume . Accordingly, the diffraction peak q corresponding to the period between neighboring particles shifts to higher values when increasing the concentration of GO from 0.5 to 5 wt% (Figure c). The evolution of d with the inverse of the volume fraction (φ) holds a linear relationship as: d = t/φ , where t is the thickness of the diffracting elements forming the LC phase .…”

Buckling, crumpling, and tumbling of semiflexible sheets in simple shear flow

“…At high Reynolds number, one example of fluid-structure interactions with 2D objects that has attracted researchers' attention is the flapping of flags 20,21 . Relatively less work, though, has focused on the behavior of 2D semiflexible sheets in low-Reynoldsnumber flows, despite the increasing relevance of transition metal dichalogenides, graphene 22 , graphene oxide 23,24 , and 2D polymers 25,26 in advanced technologies. Xu and Green 27,28 looked at sheets under shear and biaxial extensional flow, and Babu and Stark 29 have studied tethered sheets in fluids, confirming predicted scaling laws of Frey and Nelson 30 regarding thermal fluctuations in the presence of hydrodynamic interactions.…”

“…36,37 . Furthermore, studies involving 2D materials whose functions depend significantly on coupled fluid motion are becoming more prevalent 23,[38][39][40][41][42][43][44][45] .…”

Delamination and Wrinkling of Flexible Conductive Polymer Thin Films

“…[ 16,17 ] This is a limiting factor for the performance of devices and a nuisance which needs to be avoided. On other occasions, however, this behavior can be harnessed to achieve additional functionality such as surface patterning at low cost [ 18–21 ] or to estimate the properties of materials. [ 15,17,22 ] Instabilities of thin films can be due to a variety of sources.…”