Friction of partially embedded vertically aligned carbon nanofibers inside elastomers

Vertically aligned carbon nanofibers partially embedded inside polyurethane (eVACNFs) are proposed as a robust high friction fibrillar material with a compliant backing. Carbon nanofibers with 50-150 nm in diameter and 20-30 mu m in length are vertically grown on silicon and transferred completely inside an elastomer by vacuum molding. By using time controlled and selective oxygen plasma etching, fibers are partially released up to 5 mu m length. Macroscale friction experiments show that eVACNFs exhibit reproducible effective friction coefficients up to 1. Besides high friction, the proposed fabrication method improves fiber-substrate bond strength, and enables uniform height nanofibers with a compliant backing.