Effect of Ionizing Radiation on the Properties of Superhydrophobic Silicone Surfaces

Superhydrophobic surfaces may be useful for a variety of optical applications as these surfaces exhibit high contact angles with water (>150 degrees) and low-drag. These properties prevent the accumulation of water droplets on the optical surface that would otherwise occur due to condensation or the adhesion of droplets from precipitation. Challenges to producing robust superhydrophobic surfaces for optical applications include the development of cost-effective processes that are compatible with non-planar optical substrates as well as the identification of material systems that exhibit long-term reliability. We have developed a 3D printing technology to create superhydrophobic surfaces by dispensing arrays of high aspect ratio polymeric features onto optical substrates. In this paper, superhydrophobic surfaces were prepared by dispensing silicone elastomers into arrays of features on glass substrates. These samples were exposed to either Cobalt 60 gamma-rays or 63.8 MeV protons to simulate ionization-induced total dose environments that could be experienced in some space orbits. In addition exposure to other harsh environments, including salt water and 125 degrees C temperatures were evaluated. The effects of these exposure conditions on superhydrophobic properties, as measured by slip angles, are reported. Near-term potential space applications will be discussed.