Tunable Nanochannels Fabricated by Mechanical Wrinkling/Folding of a Stiff Skin on a Soft Polymer

DOI: 10.1002/admi.201400493 wavelength and amplitude ( Figure 1 a). Further increase in the strain level triggered the transition from wrinkles to folds, creating well-defi ned closed channels with a diameter in the nanoscale range (Figure 1 b). 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 confi guration of the channels was switchable from open to closed and vice versa by controlling the strain level. We demonstrated a unique application of the tunable nanochannels for “on demand” trapping and releasing gold (Au) nanoparticles. Surface morphological changes of a substrate treated with oxygen plasma for 20 min were analyzed by in situ atomic force microscopy (AFM) with respect to the nominal strain induced in the skin. The surface morphology can be categorized into three distinctive regimes: wrinkling, transition, and folding ( Figure 2 a). In the fi rst regime, wrinkles were observed on the surface, and the wavelength (λ W ) was decreased in a relatively linear fashion with an increase in the nominal strain (Figure 2 b), while the amplitude ( A W ) was increased approximately with the square root of the nominal strain (Figure 2 c). When a PDMS substrate is subjected to large deformation, the wavelength decreases while the amplitude increases with increasing strain Nanochannels can effectively be used for manipulating nanomaterials, such as DNA, [ 1–6 ] proteins, [ 7,8 ] and nanoparticles. [ 9 ]