Vertically-aligned carbon nanotubes (VACNTs) have extraordinary structural and mechanical properties, and have been considered as potential candidates for creating dry adhesives inspired by adhesive structures in nature. Catalytic chemical vapor deposition is widely used to grow VACNTs; however, the influential mechanism of VACNT preparation parameters (such as H₂ concentration) on its adhesion property is not clear, making accurate control over the structure of VACNTs adhesive an ongoing challenge. In this article, we use electron beam-deposited SiO₂/Al₂O₃ as a support layer, Fe as catalyst, and C₂H₄/H₂ gas mixtures as a feed gas to prepare VACNTs, while varying the ratio of the reducing atmosphere (H₂) from 0% to 35%. VACNTs synthesized at a 15% H₂ concentration (5 mm × 5 mm in size) can support a maximal weight of 856 g, which indicates a macroscopic shear adhesive strength of 34 N/cm². We propose a hydrogen-concentration-dependent model for the shear adhesive performance of VACNTs. By adjusting the amount of hydrogen present during the reaction, the morphology and quality of the prepared VACNTs can be precisely controlled, which significantly influences its shear adhesive performance. These results are advantageous for the application of carbon nanotubes as dry adhesives.

The crawling process of snakes is known to have fascinating tribological phenomena, whereas investigations on their frictional properties depending on patterned cuticles are insufficient. In this study, we have designed and fabricated biomimetic microstructures inspired by the geometric microunits of Achalinus spinalis cuticle using polyurethane acrylate (PUA) material and performed its tribological analysis. The micro-morphology of this Achalinus-inspired textured polymer surface (AITPS) is characterized by the closely and evenly quasi-rectangular microgrooves, periodically arranged along certain orientations. We have compared the frictional performance of our fabricated AITPS with other competitive microstructure, using a smooth steel ball and commercial clay as an interacting surface. After performing massive friction tests with steel ball and clay, AITPS still maintains good resistance reduction performed compared to the patterned surface with straight microgrooves, which is most likely due to the reduction of actual contact areas at the frictional interface.