Formation of Nanowrinkles on Varied Polymers Using Reactive Ion Etching

The optical and mechanical properties of many materials can be altered by forming nanoscale structures on their surfaces, such as wrinkles, without altering the bulk properties of the materials. Such nanowrinkled materials have important applications in many fields, including the production of photodetectors and solar cells. Wrinkles are formed when compressive strain is applied to a stiff skin bonded to a softer, elastomeric main material, or substrate, causing the skin to buckle in a periodic fashion. The most commonly used method involves bonding a thin layer of metal to the substrate to create the skin. This method has trouble forming wrinkles with large amplitudes relative to their wavelengths, a trait that is desirable for many applications. A recently discovered method, however, forms nanowrinkles through altering the surface of the substrate, and has shown increased control over the average wavelength, amplitude, and orientation of the wrinkles. This is accomplished through reactive ion etching (RIE), in which the substrate is treated with plasma formed from various gases, such as argon (Ar), carbon tetrafluoride (CF4), and trifluoromethane (CHF3), creating a stiff skin . Applying this method to various polymers with different properties would be highly beneficial, with applications ranging from biomechanical work such as brain and cardiac monitors to flexible electronics for deformable transparent displays and microlens arrays.