• carbon nanotubes;
  • energy storage;
  • hybrid materials;
  • nanotechnology;
  • mechanics
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Superstrong, ultralong, individual carbon nanotubes (CNTs) are deposited with TiO2 particles and visualized under an optical microscope with excellent strain-relaxation reversibility and high fatigue resistance capability. The CNTs with perfect structures have tensile strengths of up to 200 GPa, densities to 1.34 TPa, energy density as high as 1125 Wh kg−1 and the power density can be up to 144 MW kg−1 for mechanical energy storage. The superb mechanical properties confirm the potential of an individual CNT as an effective storage medium with mechanical energy for nano-electromechanical systems, flexible devices, sensors, actuators, antennas, etc.