Enhanced mechanical properties of biomedical poly(ethylene terephthalate) surface modified by acetylene plasma immersion ion implantation-deposition

Plasma immersion ion implantation-deposition (PIII-D) as an innovative and hybrid technique has been applied for surface modification of polymeric materials, Our recent work on acetylene (C₂H₂) plasma immersion ion implantation and deposition of polyethylene terephthalate (PET) and Si (100) wafers which are placed on PET films to make the same electric contact as the PET samples reveals some encouraging results in terms of significantly increased surface hardness, elastic modulus as well as surface wettability. Further investigation shows that the improvement in mechanical properties of modified surface following C₂H₂ PIII-D modification generally increases with bias voltage. The elastic modulus and hardness of films deposited on Si wafers increase from 73.75 GPa and 5367.52 MPa to 123.51 GPa and 13223.02 Mpa when bias voltage increases from -5KV to -15KV. The change of surface structure may account for the improved mechanical properties. The structure analysis of Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy (XPS) reveal the formation of thin hydrogenated amorphous carbon (a-C:H) films with different structures and chemical bonds on the PET surface. Atomic force microscopy (AFM) shows that the reduced average surface roughness (Ra) decreases from 33.1 nm to 11.4 nm by C₂H₂ PIII-D. The wettability of the films is investigated by contact angle measurement. DLC deposited on PET shows water contact angle of 64.8° compared with 83.5° of the untreated PET. This reveals the increasing wettability of polymer surface by using C₂H₂ PIIID. This research shows PIIID exhibits a great potential for improving the surface mechanical properties of biomedical polymers.