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Discover the secret on the toes of tree frogs-- breakthrough in bionic adhesion by Xue Longjian and his team
Author:School of Power and Mechanical Engineering  Date:2017-10-18  Clicks:

ACS Nano (American Chemical Society Nano) (impact factor 13.942), the international authoritative journal in the field of materials, published the research results of Professor Xue Longjian on the bionic adhesion. Xue is a young scholar of Thousand Talents Program from School of Power and Mechanical Engineering in Wuhan University.

This essay entitled Hybrid Surface Patterns Mimicking the Design of the Adhesive Toe Pad of Tree Frog is highlighted at the headline on the website of American Chemical Society with Professor Xue as its first author.

It is known that tree frogs, the animals living in a humid environment, can jump and crawl with ease above and among the leaves of plants. This is because that the tree frog mainly relies on its toes with strong adhesion and friction, which are mainly determined by the microstructure of the toes and the mucus.

Researchers found that the microstructure of the tree frog toes is mainly pentagonal and hexagonal, and there are several microns of wide channels between the polygons. These channels allow the liquid on the contact interface to be emitted out of the contact interface to achieve direct contact between the solid for high adhesion and friction. The latest study shows that the polygonal structure of some tree frogs is actually composed of keratin nanofiber bundles.

This finding inspires Xue Longjian task group to prepare a micro-nano composite hexagonal columnar array. The structure consists of a higher modulus polystyrene (PS) nanorods and a soft silicone rubber polydimethylsiloxane (PDMS). Moreover, the PS nanorods are vertically distributed in the PDMS positive hexagonal columnar array. When there is a chemical bond between PS and PDMS, the stress can be effectively transferred between the two materials.

When the composite columnar array is disengaged from the contact surface, the presence of the PS nanorods allows the position of the maximum stress to move from the edge of the micrometer column to the center, and the stress minimum is distributed at the edge of the micrometer column. This stress distribution effectively inhibits the separation of the contact interface from the edge of the micrometer column, increasing the adhesion of the structure. The increased adhesion and relatively high structural stiffness enhance the friction of the structure. Then synchronous enhancement of the adhesion and friction is achieved in the biomolecule-like adhesive structure.

The results of this study are operational and instructive for other material systems. The imitation of the surface structure of the tree frog toes illustrates the significance of this composite structure for the survival of the tree frog, and further promotes people’s understanding about the bionic adhesion.

In recent years, Xue Longjian cooperating with foreign research teams of high-level has achieved a lot in the field of biomolecule sticky materials. Related works are published in Nature Communications, Nano Letters, Advanced Functional Materials and other magazines.

 

The paper: http://pubs.acs.org/doi/10.1021/acsnano.7b04994

Rewritten by Jing Huichao

Edited by: Shen Yuxi, Hu Sijia

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