Abstract
According to the dynamic characteristics of the adhesion desorption process between gecko-like polyurethane setae and the contact surface, the microcontact principle of an elastic sphere and plane is established based on the Johnson–Kendall–Robert model. On this basis, combined with the cantilever beam model, microscale adhesive contact models in the case of a single and an array of setae are obtained. The contact process is numerically simulated and verified by the adhesion desorption test. After that, the effects of external preload, the elastic modulus of setae material, the surface energy, and the surface roughness on the contact force and depth during the dynamic contact process of setae are studied. The results show that the error between the simulation and test is 15.9%, and the simulation model could reflect the real contact procedure. With the increase in preload, the push-off force of the setae array would grow and remain basically constant after reaching saturation. Increasing the elastic modulus of setae material would reduce the contact depth, but have little effect on the maximum push-off force; with the increase in the surface energy of the contact object, both the push-off force between the objects and the contact depth during desorption would increase. With the increase in wall roughness, the push-off force curve of the setae array becomes smoother, but the maximum push-off force would decrease. By exploring the dynamic mechanical characteristics of the micro angle of setae, the corresponding theoretical basis is provided for the numerical simulation of the adsorption force of macro materials.
Highlights
In recent years, substantial progress has been achieved in gecko-inspired adhesive technology since the discovery of the uniquely layered footpad structure of geckos [1,2].Geckos can climb on almost any surface, or even stand upright or upside down, because their layered structure is composed of inclined villi, and the end of each villus is composed of many thin setae [3]
The van der Waals force exists in the molecules on the surface of various objects without any requirements regarding the environment, so it is employed by animals such as geckos to adhere to the surfaces of various objects [9]
The root mean square (RMS) was Figure 11a shows the relationship between the adsorption force and the preload on used to describe the dispersion between the experimental data and the simulation data, and the setae array when the mean square error of the roughness was 1
Summary
Substantial progress has been achieved in gecko-inspired adhesive technology since the discovery of the uniquely layered footpad structure of geckos [1,2]. Persson proposed a simple model to study the effect of surface roughness on the adhesion of gecko foot setae. This model simplifies the tongue depressor at the end of the setae and regards the tongue depressor as an equivalent plane. We could explore the principle of the microstructure of gecko feet to study the adhesion characteristic of polyurethane setae array materials. The dynamic mechanical properties of setae in microcontact are further studied by integrating the JKR contact theory model with the cantilever beam model. Through the established mathematical model, the influence mechanism of roughness, surface energy, and elastic modulus on the microcontact dynamic characteristics of polyurethane, the setae array is analyzed.
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