Microwrinkles by deposition of aluminum onto polydimethylsiloxane

We observed the variation in the size of microwrinkles according to the number of unit processing cycles, which consist of polydimethyl siloxane (PDMS) casting followed by the deposition of Al. As the number of processing cycles increases, the width of the microwrinkles narrows and their height increases. After five processing cycles were completed, the width of the microwrinkles stood at 1.7–3.7 μm. The top surface area of the microwrinkles became smaller upon additional processing cycles, thereby reducing the contact area between the water drops and the top surface. For this reason, the contact angle increased as the number of processing cycles increased. The contact angle measured after five processing cycles was 145°, implying that the microwrinkled surface was modified such that it became superhydrophobic.

► Microwrinkles were created by exploiting the gap between the thermal expansion coefficients of the cast PDMS and the Al.
► The width of the microwrinkles was reduced as the number of processing cycles—consisting of PDMS casting and Al deposition—increased, while the height of the wrinkles increased.
► After the completion of seven processing cycles, the width of the microwrinkles ranged ~ 3.6 μm and the contact angle measured on the substrate surface was 148°.