High Aspect Ratio Wrinkles on a Soft Polymer

Sk. Faruque Ahmed, Geon-Ho Nho, Kwang-Ryeol Lee, Ashkan Vaziri and Myoung-Woon Moon
 

Most Instability of a stiff thin film attached to a compliant substrate often leads to emergence of exquisite wrinkles with length scales that depend on the system geometry and applied stresses. These patterns have vast potential applications including in tissue engineering, flexible electronics and semiconductor industry. However, one of the limiting factors in the usage of these patterns is the low amplitude/wavelength ratio that can be achieved using the current surface engineering techniques. Here, we present an effective method that allows creating wrinkles with an amplitude/wavelength aspect ratio as large as 2.5 on a soft polymer. In this method, first, the surface of a poly(dimethylsiloxane) (PDMS) is pre-patterned using Ar ion beam. Then, an amorphous carbon film gets deposited on the pre-patterned polymeric surface using glancing angle deposition (GLAD). We show that the amplitude of the created patterns can be varied between several nm to submicron size by changing the carbon deposition time, allowing us to harness patterned polymeric substrates for a variety of applications. Specifically, we demonstrate a potential application of the high aspect ratio wrinkles for changing the surface optical band gap.