The effects of various tensile velocities on nanocrack formation were studied.

A tunable nanocrack was created by mechanical stretching/compression cycles.

The tensile velocity was found to have a significant effect on the crack density.

A low detection limit of 500 ppm of H₂ in air was demonstrated.

Narrow nanocracks (w: 55–100 nm) and high crack density provides enhanced sensing properties in air.