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This and the next image are from:
So Nagashima (1), Hamid Ebrahimi (2), Kwang-Ryeol Lee (1), Ashkan Vaziri (2) and Myoung-Woon Moon (1)
(1) Institute for Multidisciplinary Convergence of Matter Korea Institute of Science and Technology
Seoul 136–791, Republic of Korea
(2) Department of Mechanical and Industrial Engineering Northeastern University
Boston, Massachusetts 02115, USA
“Tunable nanochannels fabricated by mechanical wrinkling/folding of a stiff skin on a soft polymer”, Advanced Material Interfaces, Vol. 2, 1400493, 2015, DOI: 10.1002/admi.201400493
ABSTRACT: We present a straightforward method for fabricating nanochannels that exploits a type of thin film instability called folding, which emerges during post-instability evolution of surface wrinkles. In our experiments, a flat PDMS substrate was uniaxially stretched and treated with oxygen plasma for varying durations, resulting in formation of a stiff-oxidized skin of varying thickness on the surface. Thereafter, the stretch was released to induce a compressive strain, defined as the change in length per unit of the initial length of the substrate, in the skin. At small strain levels, wrinkles appeared on the substrate surface, forming open channels with a specific wavelength and amplitude. Further increase in the strain level triggered the transition from wrinkles to folds, creating well-defined closed channels with a diameter in the nanoscale range. The characteristic dimensions of the channels such as wavelength, amplitude, and diameter were robustly tunable by changing the duration of oxygen plasma treatment and strain level. Furthermore, the configuration of the channels was switchable from open to closed and vice versa by controlling the strain level.
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