Transfer of vertically aligned carbon nanotube arrays onto flexible substrates for gecko-inspired dry adhesive application

Abstract

The gecko's extraordinary climbing ability has inspired scientists to develop synthetic dry adhesives that mimic the structure and function of gecko feet. The vertically aligned carbon nanotube (VACNT) array has been considered a potential candidate for developing gecko-inspired dry adhesive materials due to its outstanding structural and mechanical properties. However, the limited choices of growth substrates and poor interfacial bonding between VACNTs and growth substrates have restricted their application as gecko-inspired dry adhesive materials. Here, we report a versatile transfer method for transferring VACNT arrays onto flexible polymer substrates using a thermal oxidation process. This transfer method mainly focused on using the VACNT array as a gecko-inspired dry adhesive. Using the transfer method developed in our study, VACNT array-based gecko-inspired dry adhesive materials with improved adhesion property, structural stability, and self-cleaning ability can be developed. A thermal oxidation process was used to obtain free-standing VACNT arrays, resulting in the production of top-transferred and bottom-transferred structural VACNT array-based dry adhesive materials. The shear adhesive strength of the transferred VACNT array was enhanced using this method. The interfacial bonding strength of the transferred VACNT array increased nearly 15 times according to nanoscratch tests. The flexible structure of the transferred VACNT array exhibited better antifouling properties by mimicking digital hyperextension (DH) motion, which is a natural peeling motion of the gecko foot with a unique dynamic self-cleaning mechanism. These findings show that our method is an efficient method for transferring VACNT arrays and an important process for fabricating gecko-inspired VACNT array-based dry adhesive materials with high structural stability, self-cleaning ability, and high adhesive strength.