Fig. 2. (A) Schematic depiction of wrinkle formation starting from a flat elastomeric PDMS substrate that is stretched and subsequently treated with oxygen plasma to form a thin silicon dioxide layer. Wrinkles form upon relaxation due to a mechanical mismatch between the bulk elastomer and the oxide top layer. (B) Amplitude (left axis and marked by circles) and periodicity (right axis and marked by rectangles) plotted vs. plasma dose of the applied post-treatment procedure (plotted lines are guides to the eye). (C) Corresponding AFM image of the wrinkled substrate after post-treatment (please note that for better comparison all images were scaled to the same height). (D) Corresponding cross-sections of the wrinkles after post-treatment, revealing a linear decrease in amplitude while the periodicity remains constant.