Nature is an excellent teacher – even for material scientists. Researchers, including scientists at the Max Planck Institute of Colloids and Interfaces, have now observed a remarkable mechanism by which polymer materials are formed. In order to capture prey, velvet worms shoot out a sticky secretion that stiffens into strong threads under the action of force. The extraordinary thing about these threads is that they can be dissolved and then reformed again. The fact that reversible polymer fibres can be drawn from the previously liquid secretion is a very interesting concept for researchers. It is quite possible that one day it will be possible to synthesize novel recyclable materials based on the principle of velvet worms.
Some animals produce amazing materials. Spider silk, for example, is stronger than steel. Mussels secrete byssus threads, which they use to cling tightly to stones under water. The material secreted by velvet worms is no less impressive. These small worm-like animals, which look like a cross between an earthworm and a caterpillar, spray a sticky liquid to ward off enemies or catch prey that is particularly deadly for prey such as woodlice, crickets and spiders: As soon as they try to wriggle out of the slimy threads, their struggles cause the threads to harden, leaving no hope of escape.
“The shear forces generated by the prey’s struggles cause the slime to harden into stiff filaments,” explains Alexander Bär, a doctoral student at the University of Kassel, who is studying under the velvet-worm expert Georg Mayer. In order to investigate the slime of an Australian velvet worm species, the biologist worked closely with researchers from the Max Planck Institute of Colloids and Interfaces in Potsdam. The chemist Stephan Schmidt, for example, now a junior professor at Heinrich Heine University in Düsseldorf, helped to elucidate the nanostructure of the slime. A research group headed by biochemist Matt Harrington in the Biomaterials Department of the Potsdam Institute focused on other questions concerning the chemical composition and molecular processing. The interdisciplinary group of scientists was particularly interested in how the composition and structure of the secretion changes during thread formation.