Contact line dynamics of a superhydrophobic surface: application for immersion lithography

The dynamic contact line behavior of water on nanotextured rough hydrophobic and superhydrophobic surfaces is studied and contrasted to smooth hydrophobic surfaces for application in immersion lithography. Liquid loss occurs at the receding meniscus when the smooth substrate is accelerated beyond a critical velocity of approximately 1 m/s. Nanotexturing the surface with average roughness values even below 10 nm results in critical velocity larger than 2.5 m/s, the upper limit of the apparatus. This unexpected increase in critical velocity is observed for both sticky hydrophobic and slippery superhydrophobic surfaces. The authors attribute this large increase in critical velocity both in increased receding contact angle and in increased slip length for such nanotextured surfaces.