Scientists Create Carbon-Nanotube Foam That “Remembers” Exactly How Hard It Was Hit

Scientists created a carbon-nanotube foam that "remembers" how it was squeezed, demonstrating a form of persistent mechanical memory. The foam, made from vertically aligned multiwalled carbon nanotubes, retained its shape and mechanical properties even after being compressed and released, unlike conventional cushioning materials. The material showed return point memory, similar to magnetic hysteresis in hard drives, and could be used to control the speed of impact waves. The foam, which was only 0.2 inches wide, retained a stable mechanical memory, and its behavior was not affected by compression speed or deformation rate. This could lead to smarter helmets, shock-absorbing liners, and mechanical computers that process signals without electronics.

• The foam retained a stable mechanical memory, unlike conventional cushioning materials.
• The material showed return point memory, analogous to magnetic hysteresis in hard drives.
• The foam's behavior was not affected by compression speed or deformation rate.

The foam's memory was not stored in electronic components or mechanical pieces but in nanoscale friction between neighboring nanotubes. The researchers developed a deformation-dependent stick-slip friction model that reproduced the observed recovery, hysteresis, and return point memory. The material's memory was reusable, not a permanent record of every force it has experienced. The foam's ability to store and act on information without electronics was demonstrated through experiments.

• The foam's memory was stored in nanoscale friction between nanotubes.
• The material's memory was reusable, not a permanent record of every force it has experienced.
• The foam's behavior was not affected by compression speed or deformation rate.

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