Finding the source of their durability: Many high-strength materials can fail after repeated exposure to subcritical loading; therefore, understanding the causes of fatigue is key to extending the longevity of the material in use. Bai et al. used chemical vapor deposition to produce centimeter-long carbon nanotubes. They then decorated these nanotubes with titanium dioxide nanoparticles for optical visualization and studied them using noncontact acoustic resonance tests. The authors determined that fatigue lifetime is dependent on the formation of the first defects on straining and is higher at lower temperatures. Science , this issue p. 1104

Great effort has been applied to scientific research on the controllable synthesis of carbon nanotubes (CNTs) with high semiconducting selectivity or high areal density toward the macroscale applications of high-performance carbon-based electronics. However, the key issue of compatibility between these two requirements for CNTs remains a challenge, blocking the expected performance boost of CNT devices. We report an in situ acoustic-assisted assembly of high-density monochromatic CNT tangles (m-CNT-Ts), consisting of one self-entangled CNT with a length of up to 100 mm and consistent chirality. On the basis of a minimum consumed energy model with a Strouhal number of approximately 0.3, the scale could be controlled within the range of 1 × 10⁴ to 3 × 10⁴ μm² or even a larger range. Transistors fabricated with one m-CNT-T showed an on/off ratio of 10³ to 10⁶ with 4-mA on-state current, which is also the highest on-state current recorded so far for single CNT–based transistors. This acoustic-assisted assembly of chiral-consistent m-CNT-Ts will provide new opportunities for the fabrication of high-performance electronics based on perfect CNTs with high purity and high density.