Carbon nanotube foams reveal a new kind of mechanical memory

Amazing stuff! More than a curiosity, I presume!

"... a foam made of carbon nanotubes that remembers exactly how hard it was squeezed, then returns to its original shape with no lasting damage. ...

To search for such a material, ... team turned to foams made of vertically aligned carbon nanotubes. They repeatedly compressed the foam until its response stabilized, then tracked how it behaved under partial unloading and reloading.

The foam displayed "return-point memory": When pushed partway, released, then pushed again, it returns to the exact mechanical state it was in before. ..."

From the abstract:

"Mechanical memory and computing are gaining significant traction as potential means to complement traditional electronics for robust and energy efficient performance in extreme environments.

However, progress has largely focused on bistable metamaterials, while traditional constitutive memory phenomena have been largely overlooked—primarily due to the absence of compelling experimental demonstrations in elastically recoverable materials.

Here, we report constitutive return point memory (RPM) in elastically recoverable, vertically aligned carbon nanotube (VACNT) foams, analogous to magnetic hysteresis-based RPM utilized in hard drives.

Unlike viscoelastic fading memory, VACNTs exhibit nonvolatile memory arising from rate-independent nanoscale friction. We find that the interplay between RPM and frictional dissipation enables independent tunability of the VACNTs’ dynamic modulus, allowing for both on-demand softening and stiffening.

We leverage this property to experimentally demonstrate tunable wave speed in a VACNT array with elastic interlayers, paving the way for novel shock limiters, elastodynamic lensing, and wave-based analog mechanical computing."

Carbon nanotube foams reveal a new kind of mechanical memory

Nanotube Material Has Perfect Memory "A carbon nanotube foam springs back to its initial state, regardless of the speed of the compression, a property that could lead to a new type of shock absorber."

Enduring Mechanical Memory from the Constitutive Response of Elastically Recoverable Nanostructured Materials

Perfect padding. Vertically aligned carbon nanotube (VACNT) foam can be synthesized into cushion-like cylinders that are roughly 5 mm wide (left). Microscope images of the foam reveal a “forest” of fibers, each of which consists of multiple carbon nanotubes (right).

Fig. 1 Fading memory and return point memory.

Total recoil. Researchers tested the stress response of VACNT foams when a compressive strain is applied. The results show that the material retains a mechanical memory that doesn’t fade.