Interfacial shear stress between single-walled carbon nanotubes and gold surfaces with and without an alkanethiol...

A novel and effective technique is developed to make the first determination of shear stress between dielectrophoretically assembled single-walled carbon nanotubes (SWNTs) and surfaces. The results demonstrate that we can vary the shear stress by a factor of 20 by functionalizing a gold surface with different alkanethiols. The interfacial shear stress between a small bundle of SWNTs and a gold surface with and without self-assembled monolayers of alkanethiol (2-phenylethanethiol or 2-aminoethanethiol) is determined. The measurements are based on simple NEMS cantilever beams, a nanomanipulator, and a scanning electron microscope (SEM). It is emphasized that the measured quantity is the slack in the nanotube (not the shear stress) induced by the nanomanipulation. The shear stress is determined from the slack through a mechanics model. An average shear stress of 87 MPa between SWNTs and gold surfaces is obtained. For the tests on the self-assembled 2-aminoethanethiol surface, an average shear stress of 142 MPa is obtained. For the self-assembled 2-phenylethanethiol surface, the shear stress is determined to be around 7.2 MPa with an estimated work of adhesion of 0.5 J/m(2).