Surface energy control of polymeric materials for contamination elimination in space environment

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The surface modification of polymeric materials by using hyperthermal atom beam was made in order to control contact angles of water relevance to contamination in low Earth orbit space environment. Two types of atom beam were currently used for a surface modification, i.e., atomic oxygen and atomic fluorine with translational energies ranging 5 to 10 eV. The translational energies in this range became available after laser detonation-induced beam formation technology was established for space environmental simulation purpose. In the present study, we used this new technology to control the surface free energy of polymers. This new technology also allows us to make low-temperature, damage-free surface modification without any charge-induced problems. From the experimental results obtained in this study, it was confirmed that the oxygen and fluorine concentrations increased with beam exposures. The formation of CF, CF_2 and CF_3 bonds were detected by X-ray photoelectron spectroscopy (XPS) when atomic fluorine beam was used to modify the surface, whereas carbonyl and carboxyl groups were formed when a polymer surface was exposed to atomic oxygen beam. It was demonstrated that the advancing contact angles of water both at polyimide and low-density polyethylene could be tunable between 60 and 135 degree by using this technique without major change of surface roughness. The capability of pattern formation of micro-scale flow channel at polymer surfaces using metal masks demonstrated the capability for avoiding contamination on polymer surfaces using this technique.