Configuration dependence of softmatter sliding friction

Recently, the study of the soft-matter sliding friction is increasing its importance. For example, lubrication of joints and digestive system is key issue when we make them artificially. But the mechanism of these systems is not well-understood yet. We focused on the structural dependence of soft-matter sliding friction which contains lubrication. We use rheometer for measurement in this experiment. Changing the thickness of the rubber, we measured torque(M) and normal force(N). From these values, we estimated the factional coefficient(μ=3M/2aN). Results are shown in Fig1,2. We discovered the transition of factional coefficient between 1mm rubber and 5mm rubber. In the intermediate rotational speed, the differential of factional coefficient is about 102. This differential is explained by the difference of lubricating condition.