Carbon nanotube foams reveal a new kind of mechanical memory

Researchers at the University of Wisconsin–Madison have discovered a novel material that can store mechanical memory: a foam composed of vertically aligned carbon nanotubes. In their study published in Physical Review X, they demonstrated that this material exhibits "return-point memory," meaning it can return to its original mechanical state after being squeezed and released, without any permanent deformation or damage.

This material represents a significant advancement over traditional computer designs that rely on bistable structures, which can only function in two states, like a simple switch. The carbon nanotube foam, however, allows for more nuanced and continuous memory, similar to how magnetic hard drives store information. The foam's ability to retain its shape without fading or relaxation over time is attributed to friction at the nanoscale level, where neighboring nanotubes stick and slip against each other as the material compresses.

Interestingly, the researchers found that the mechanical properties of the foam could be tuned in two ways: by squeezing it harder, the foam becomes stiffer, and by shaking it, the foam becomes softer. This tunability opens up new possibilities for applications beyond simple memory storage, such as shock absorption, vibration filtering, or even passive computing.

The team suggests that the friction-based approach used in this study could inspire similar developments in other materials, potentially leading to a wider range of foams and fibers capable of remembering mechanical forces.