Surface properties of vertically aligned carbon nanotube arrays

This study focuses on the structural changes of vertically aligned carbon nanotube (CNT) arrays while measuring their adhesive properties and wetting behaviour. CNT forests grown by chemical vapor deposition with a height of similar to 100 mu m, an outer CNT diameter of similar to 10 nm and a density of the order of similar to 10(10) CNTs/cm(2) show an average adhesion of 4 N/cm(2) when pressed against a glass Surface. The applied forces lead to the collapse of the regular CNT arrays which limits their reusability as functional dry adhesives. Goniometric water contact angle (CA) measurements oil CNT forests show a systematic decrease frorn an initial value of similar to 126 degrees to a final CA similar to highly orientated graphite. Environmental scanning electron microscopy shows that this loss of hydrophobicity is due to an evaporation induced compaction of CNTs together with the loss of their vertical alignment. We observe the formation of cellular patterns for controlled drying. (c) 2007 Elsevier B. V. All rights reserved.