Contact Friction Regulation of the UV Laser Textured PVA Hydrogel and Titanium Alloy Interface

Abstract The soft, hydrophilic and smooth surface of hydrogel displays extremely complex friction behavior. In this work, the ultraviolet laser post-processing created PVA hydrogel surface textures is found to be a one-step effective way for the contact friction regulation at the hydrogel-titanium alloy interface. Micro-grooves with various spacings and depths are fabricated by adjusting the laser scanline interval, laser energy density and the scanning times. Friction torques are measured by a strain-controlled parallel-plate rheometer to characterize frictional behaviors of micro-grooves. At the sliding velocity range of 0.085mm/s < v < 2.3mm/s, the effect of interlocking and ploughing force are the dominant origins of friction. Frictional stress increases with the decrease of the micro-groove spacing, but not with the increase of the micro-groove depth, which indicates that frictional stress doesn’t simply increase with an increase of hydrogel’s roughness. As the velocity increases from 2.3mm/s to 100mm/s, the surface wettability of textured hydrogel plays an important role in regulating friction. Both smooth hydrogel and laser textured hydrogels show stick-slip phenomenon which occurs in the same velocity range. These results take us a step closer to deriving a more effective, accurate, and dependable guideline for designing laser-textured surface grooves for sliding friction control of hydrogel applications.