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.
Complexity, rate, and scale in sliding friction dynamics between a finger and textured surface
