Schaber Clemens F, Filippov Alexander E, Heinlein Thorsten, Schneider Jörg J, Gorb Stanislav N
Functional Morphology and Biomechanics, Zoological Institute , Kiel University , Am Botanischen Garten 1-9, 24118 Kiel , Germany.
Functional Morphology and Biomechanics, Zoological Institute , Kiel University , Am Botanischen Garten 1-9, 24118 Kiel , Germany ; Department of Electronic and Kinetic Properties of Non-linear Systems , Donetsk Institute for Physics and Engineering, National Academy of Sciences , 83114 Donetsk , Ukraine ; FG Systemdynamik und Reibungsphysik , Technische Universität Berlin, Institut für Mechanik , Sekr. C8-4, Raum M 122, Straße des 17. Juni 135, 10623 Berlin , Germany.
Interface Focus. 2015 Aug 6;5(4):20150026. doi: 10.1098/rsfs.2015.0026.
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.
先前的研究表明，垂直排列的碳纳米管（VACNTs）阵列具有很强的摩擦特性。实验表明，在对同一VACNT点进行重复测量时，摩擦系数从第一个滑动周期到第二个滑动周期有显著下降，但在连续周期中保持稳定值。在摩擦测试中施加剪切力时，VACNTs会形成簇，自组织作用使阵列的机械性能稳定。在摩擦测试期间，垂直施加到阵列表面的载荷在300 μN至4 mN范围内增加时，簇的尺寸会增大，而摩擦系数会减小。为了更好地理解实验结果，我们构建并对一个简约模型进行了数值研究，该模型用最少的可调参数再现了系统的主要特征。我们使用著名的莫尔斯势函数计算球形摩擦探针与阵列束之间的范德华力，以预测簇的数量、大小、瞬时摩擦力和平均摩擦力，以及VACNTs在连续滑动周期和不同法向载荷下的行为。模型计算得到的数据与实验数据非常吻合，有助于使VACNT阵列适用于仿生应用。
