Feature and the characteristic of sliding resistance reduction of the earthworm’s non-smooth surface

The earthworm (Eisenia foetida) was used as research object, and three surface specimens: motionless, extending and shrinking were prepared. The surface feature of the earthworm was analyzed by using the OLYMPUS stereo microscope and its image analysis system OLYCIATM M3. The results showed that the earthworm surface was typical wavy non-smooth structure, the body department texture was small and dense, while the forehead texture was big and thin, and the non-smooth unit density of the body department was bigger than that of the forehead. The ratio of the width and height of the non-smooth structure unit about the forehead motionless, extending and shrinking specimens were 1.65:1:0.78 and 0.23:1:1.27, respectively, while those of the body surface specimens were 1.65:1:0.81 and 0.33:1:1.28, respectively. The sliding resistance experiments of earthworm’s unfolding surface specimens and steel specimens were conducted by means of a tiny adhesion testing system. The test results showed that the shrinking specimen had the best reducing sliding resistance ability, then was motionless specimen and the extending specimen, respectively. The reducing sliding resistance ability of the forehead was better than that of the body. Compared with the steel specimen, the rate of reducing sliding resistance of the forehead and the body shrinking were 39% and 29%, respectively. This study will afford basic data for bionic research of biologic non-smooth surface and exposing biomimetic coupling mechanism.