posted on 2017-06-05, 00:00authored byYinlong Tan, Zengyong Chu, Zhenhua Jiang, Tianjiao Hu, Gongyi Li, Jia Song
Gyrification in the human brain is
driven by the compressive stress
induced by the tangential expansion of the cortical layer, while similar
topographies can also be induced by the tangential shrinkage of the
spherical substrate. Herein we introduce a simple three-dimensional
(3D) shrinking method to generate the cortex-like patterns using two-dimensional
(2D) graphene oxide (GO) as the building blocks. By rotation-dip-coating
a GO film on an air-charged latex balloon and then releasing the air
slowly, a highly folded hydrophobic GO surface can be induced. Wrinkling-to-folding
transition was observed and the folding state can be easily regulated
by varying the prestrain of the substrate and the thickness of the
GO film. Driven by the residue stresses stored in the system, sheet-to-tube
actuating occurs rapidly once the bilayer system is cut into slices.
In response to some organic solvents, however, the square bilayer
actuator exhibits excellent reversible, bidirectional, large-deformational
curling properties on wetting and drying. An ultralarge curvature
of 2.75 mm–1 was observed within 18 s from the original
negative bending to the final positive bending in response to tetrahydrofuran
(THF). In addition to a mechanical hand, a swimming worm, a smart
package, a bionic mimosa, and two bionic flowers, a crude oil collector
has been designed and demonstrated, aided by the superhydrophobic
and superoleophilic modified GO surface and the solvent-responsive
bilayer system.