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Modelling clustering of vertically aligned carbon nanotube arrays.

Schaber CF, Filippov AE, Heinlein T, Schneider JJ, Gorb SN - Interface Focus (2015)

Bottom Line: Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties.To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters.The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications.

View Article: PubMed Central - PubMed

Affiliation: Functional Morphology and Biomechanics, Zoological Institute , Kiel University , Am Botanischen Garten 1-9, 24118 Kiel , Germany.

ABSTRACT
Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications.

No MeSH data available.


Related in: MedlinePlus

Clusters of VACNTs after friction tests with normal loads of (i) 289 µN, (ii) 673 µN and (iii) 3860 µN; top view scanning electron microscopy images (a) and schematic side views (b) of the surface of the arrays. The curve in b(i) depicts the surface of the spherical probe and the arrow points in sliding direction during friction tests.
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RSFS20150026F1: Clusters of VACNTs after friction tests with normal loads of (i) 289 µN, (ii) 673 µN and (iii) 3860 µN; top view scanning electron microscopy images (a) and schematic side views (b) of the surface of the arrays. The curve in b(i) depicts the surface of the spherical probe and the arrow points in sliding direction during friction tests.

Mentions: Here we examined the clustering behaviour of 1 mm long arrays of vertically aligned multi-walled carbon nanotubes (VACNT) firmly bound to a substrate, which are good candidates for mimicking gecko foot hairs [9]. The thickness of single carbon nanotubes (CNTs) of between 5 and 20 nm is well in the range of that known for contact elements of gecko hairs [10]. The experimentally determined coefficient of friction on pristine surfaces of VACNT arrays is very high. It decreases with consecutive sliding cycles on the same location to still remarkably stable values. This decrease of friction is accompanied by clustering of the VACNTs, which stabilizes the mechanical properties of the arrays [11]. The size of the clusters depends on the normal force applied on the sample during friction tests (figure 1).Figure 1.


Modelling clustering of vertically aligned carbon nanotube arrays.

Schaber CF, Filippov AE, Heinlein T, Schneider JJ, Gorb SN - Interface Focus (2015)

Clusters of VACNTs after friction tests with normal loads of (i) 289 µN, (ii) 673 µN and (iii) 3860 µN; top view scanning electron microscopy images (a) and schematic side views (b) of the surface of the arrays. The curve in b(i) depicts the surface of the spherical probe and the arrow points in sliding direction during friction tests.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4590422&req=5

RSFS20150026F1: Clusters of VACNTs after friction tests with normal loads of (i) 289 µN, (ii) 673 µN and (iii) 3860 µN; top view scanning electron microscopy images (a) and schematic side views (b) of the surface of the arrays. The curve in b(i) depicts the surface of the spherical probe and the arrow points in sliding direction during friction tests.
Mentions: Here we examined the clustering behaviour of 1 mm long arrays of vertically aligned multi-walled carbon nanotubes (VACNT) firmly bound to a substrate, which are good candidates for mimicking gecko foot hairs [9]. The thickness of single carbon nanotubes (CNTs) of between 5 and 20 nm is well in the range of that known for contact elements of gecko hairs [10]. The experimentally determined coefficient of friction on pristine surfaces of VACNT arrays is very high. It decreases with consecutive sliding cycles on the same location to still remarkably stable values. This decrease of friction is accompanied by clustering of the VACNTs, which stabilizes the mechanical properties of the arrays [11]. The size of the clusters depends on the normal force applied on the sample during friction tests (figure 1).Figure 1.

Bottom Line: Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties.To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters.The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications.

View Article: PubMed Central - PubMed

Affiliation: Functional Morphology and Biomechanics, Zoological Institute , Kiel University , Am Botanischen Garten 1-9, 24118 Kiel , Germany.

ABSTRACT
Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications.

No MeSH data available.


Related in: MedlinePlus