I guessed this might be buckthorn, but no

cellulose nanocrystals (CNC)

from the article:

"At the nanoscale, CNCs are stronger and stiffer than Kevlar. If the crystals could be worked into materials in significant fractions, CNCs could be a route to stronger, more sustainable, naturally derived plastics."

the original paper:

Printable, castable, nanocrystalline cellulose-epoxy composites exhibiting hierarchical nacre-like toughening

<https://link.springer.com/article/10.1007/s10570-021-04384-7> (paywall)