The effect of contact length on adhesion between carbon nanotubes on silicon dioxide

The force of adhesion was measured for single walled carbon nanotubes grown over lithographically defined silicon dioxide trenches. We varied contact lengths between the nanotubes and silicon dioxide from $230to850nm$⁠. Suspended nanotubes were pushed vertically into the trenches with an atomic force microscope tip, causing them to slip along the surface. Previous work done at shorter contact lengths found that tension was constant with contact length [J. D. Whittaker et al., Nano Lett. 6, 953 (2006)]. This study finds that when the nanotube contact length approaches $1μm$⁠, the tension at which nanotubes slip begins to increase with contact length. This indicates that contact length independent adhesion is a uniquely nanoscale behavior.