Preliminary Study on Tribological Behavior and Self-repairing Mechanism of Keratin Tissues

The tribological behaviors and deformation recovery of fingernails and chicken claws are preliminarily investigated using nano-indentation/scratch tester and Vickers hardness instrument. Experimental results indicate that the tribological properties of keratin tissues strongly depend on their microstructures. Because of the better fiber orientation, the friction coefficient on fingernail is a little lower than that on chicken claws at the same loading conditions. On the cross section of nail, even though the friction coefficient during scratching in the direction perpendicular to fibers is greater than that parallel to fibers, the scratch width is smaller. Moreover, due to the different structures and properties between the inner and outer of claw, the latter presents higher friction coefficient and smaller scratch width. Finally, both the indentation and scratch deformation of nail and claw under low load can be fully recovered after being immersed in water for 5 minutes and 30 minutes, respectively.