Measurement of sliding friction coefficient of micro-line patterned surfaces on ice

Although the sliding friction of patterned surfaces on ice has been investigated for over a century, physical analysis still needs to be improved. In this study, we investigate the friction coefficient on ice by changing the experimental conditions of temperature, gap between line patterns (20 μm and 200 μm), and sliding direction. In the temperature region of -17.7 °C < T <-2.5 °C, a longer gap (200 μm) patterned surface has a lower friction coefficient for both parallel and perpendicular sliding directions at the same temperatures. Interestingly, a lower friction coefficient is found when the sliding direction is perpendicular to the micro-structure patterns at T < -7.6 °C for gap = 20 μm and at T < -9.9 °C for gap = 200 μm. To understand this interesting phenomenon, a theoretical model is derived by modifying the model from the study by Oksanen and Keinonen. Based on this modified model, the surface with a shorter gap (20 μm) makes fewer contacts and the pattern direction determines the water layer elongation at each contact. This validates that friction on ice can be controlled using a micro-structure pattern and moreover suggests a method for finding an optimized micro-structured surface for reducing friction on ice.