R. D. Kamien, S. Yang and A. G. Yodh
Building complex three-dimensional (3D) materials from pre-programmed two-dimensional films presents exciting challenges and opportunities. To achieve this goal, researchers inspired by the paper folding techniques of origami and kirigami have successfully utilized the mechanical instabilities of thin films, such as buckling.
This research study pushed beyond “flat films” and explored the role of topography in the swelling-induced buckling of bilayer films. To demonstrate the concept, we first created stripe patterns (by replica molding) on one-side of the swellable polymer (PDMS) film. Then a thin layer of non-swelling parylene was deposited uniformly onto the molded side of the PDMS. After swelling, the bilayer films buckle because of mismatched swelling ratios between the PDMS and parylene. Interestingly, simple topographic patterns on the bilayer film (like stripes) can lead to novel 3D structures, including half-pipes, helical tubules, and ribbons, all controlled via a few physical constraints.
The new research helps us better understand the role of topography in mechanical instabilities and introduces a simple method to harness instabilities to create desired 3D structures.
Jeong, Cho, Lee, Gong, Kamien, Yang, and Yodh, Topography-guided buckling of swollen polymer bilayer films into three-dimensional structures. Soft Matter 13, 956-962 (2017)