Photopatternable Superhydrophobic Nanocomposites for Microfabrication

In this paper, we first report on direct-photolithography-based microfabrication of transparent super-hydrophobic micropatterns using novel photodefinable nanocomposites, combining the nanomorphology and hydrophobicity of polytetrafluoroethylene (PTFE) nanoparticles and the photopatternability and transparency of an SU-8 photoresist using both direct-mixing and coating-immobilization methods. The direct mixture of PTFE-SU-8 nanocomposite can be reliably spin-coated and photopatterned onto transparent substrates (e.g., glass or polymers) with a minimal feature resolution of 50 ??m. The resulting nanocomposite film possesses a contact angle of water at 150??, although its optical transparency is less than 30%. Furthermore, a modified coating-immobilization approach, employing spray coating and thermal immobilization of PTFE nanoparticles onto an SU-8 polymer matrix, significantly enhances superhydrophobicity, lithography resolution, as well as optical transparency. The highest optical transparency of 80% and a minimal feature resolution of 10 ??m have been achieved using the standard photolithography approach, while the contact angle of water above 165?? enables extraordinary superhydrophobicity with low hysteresis. The novel PTFE-SU-8 nanocomposites provide a unique combination of superhydrophobicity, optical transparency, and photopatternability, along with excellent adaptability and simple processability, which offer great extension to rapidly evolving micro-nanoengineering applications.