Tuning carbon nanotube bandgaps with strain
  We show that the band structure of a carbon nanotube (NT) can be dramatically altered by mechanical strain. We employ an atomic force microscope tip to simultaneously vary the NT strain and to electrostatically gate the tube. We show that strain can open a bandgap in a metallic NT and modify the bandgap in a semiconducting NT. Theoretical work predicts that bandgap changes can range between +100meV and -100meV per 1% stretch, depending on NT chirality, and our measurements are consistent with this predicted range. 
E. D. Minot, Yuval Yaish, Vera Sazonova, Ji-Yong Park, Markus Brink,   Paul L. McEuen