Effects of surface roughness on the van der Waals force between macroscopic bodies

Three forms of animals’ adhesion were analyzed: hairy adhesive pads, smooth adhesive pads and claw. Scanning electron microscope (SEM) was used to observe the surface of friction plate with different particle diameters. It’s found that the particle could be seen as conical shape. The self-designed lever-like testing equipment was also used to measure the adhesive force of drosophila melanogaster contacting 6 substrates with different roughness. It was shown that adhesive force decreased first and finally rose with the increase of surface roughness. When the roughness (R value) was about 68.5nm, it showed that the lowest adhesive force was 0.0085mN. Then model of the Van der Waals force was established. In this model, contact form between seta and the substrate was divided into five states, and the theoretical adhesive force at each state was calculated, which successfully simulated with the actual value. However, when surface roughness reached the situation that the gap between adjacent particles was greater than 2μm, the gripping function of the claw made the actual value greater than theoretical one. It was concluded that adhesive force was a compound function of the Van der Waals force generated by hairy adhesive force and the gripping force generated by claw. So it was also speculated that the fibrous fine pads of insects were the basic form adhesion on smooth surface of the substrate.

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First direct measurement of van der Waals force

AccessScience ◽

10.1036/1097-8542.br0718131 ◽

2015 ◽

Keyword(s):

Direct Measurement ◽

Van Der Waals ◽

Van Der Waals Force

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FLUCTUATION-INDUCED RADIATIVE HEAT TRANSFER AND VAN DER WAALS FORCE FOR SPHERICAL SHAPES

Proceeding of First Thermal and Fluids Engineering Summer Conference ◽

10.1615/tfesc1.fnd.012853 ◽

2016 ◽

Author(s):

Yi Zheng ◽

Alok Ghanekar

Keyword(s):

Heat Transfer ◽

Radiative Heat Transfer ◽

Radiative Heat ◽

Van Der Waals ◽

Van Der Waals Force

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First-Principles Study on Graphene/Mg2Si Interface of Selective Laser Melting Graphene/Aluminum Matrix Composites

Metals ◽

10.3390/met11060941 ◽

2021 ◽

Vol 11 (6) ◽

pp. 941

Author(s):

Zhanyong Zhao ◽

Shijie Chang ◽

Jie Wang ◽

Peikang Bai ◽

Wenbo Du ◽

...

Keyword(s):

Interfacial Energy ◽

First Principles ◽

Lattice Mismatch ◽

Van Der Waals ◽

Aluminum Matrix ◽

Van Der Waals Force ◽

Aluminum Matrix Composites ◽

Matrix Composites ◽

Charge Density Difference ◽

Interface Charge

The bonding strength of a Gr/Mg2Si interface was calculated by first principles. Graphene can form a stable, completely coherent interface with Mg2Si. When the (0001) Gr/(001) Mg2Si crystal plane is combined, the mismatch degree is 5.394%, which conforms to the two-dimensional lattice mismatch theory. At the interface between Gr/Mg2Si, chemical bonds were not formed, there was only a strong van der Waals force; the interfaces composed of three low index surfaces (001), (011) and (111) of Mg2Si and Gr (0001) have smaller interfacial adhesion work and larger interfacial energy, the interfacial energy of Gr/Mg2Si is much larger than that of α-Al/Al melt and Gr/Al interfacial (0.15 J/m2, 0.16 J/m2), and the interface distance of a stable interface is larger than the bond length of a chemical bond. The interface charge density difference diagram and density of states curve show that there is only strong van der Waals force in a Gr/Mg2Si interface. Therefore, when the Gr/AlSi10Mg composite is stressed and deformed, the Gr/Mg2Si interface in the composite is easy to separate and become the crack propagation source. The Gr/Mg2Si interface should be avoided in the preparation of Gr/AlSi10Mg composite.

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