Using UV laser surface treatment to modify the wettability characteristics of polyamide 6,6 and its effects on osteoblast cell activity

Lasers can be used to modify the surface characteristics of a number of different materials for many applications. This paper details the way in which a KrF 248 nm excimer laser can be utilized to surface pattern and whole area irradiate nylon 6,6. 50 and 100 µm dimensioned trench and hatch patterns were induced in addition to the whole area irradiative processing which covered an area of 3.75 cm2 with fluencies ranging from 26 to 70 mJcm-2. The surface topography and roughness were determined with the use of a white light interferometer. From this it was found that the largest roughness, Sa, was 1.53 µm which arose from the 100 µm hatch excimer patterned sample. Wettability characteristics were obtained for each sample using a sessile drop device in which it was observed that the contact angle increased by up to 25° for the patterned samples and decreased by up to 15° for the large area processed samples. It is believed that the observed increase in contact angle can be attributed to the likely existence of a mixed-state wetting regime in which both Wenzel and Cassie-Baxter regimes are present over the liquid-solid interface. As a result of the small variation in surface roughness for the large area processed samples the observed decrease in contact angle can be explained by a modification of the surface chemistry and an increase in polar component (γp) and total surface energy (γT). Osteoblast cell activity was analyzed by carrying out cytotoxicity and alkaline leukocyte phosphatase (ALP) activity experiments, two major factors which are linked to sufficient cell growth and proliferation.