Nanofibers have found use in numerous applications, ranging from lightweight car parts to high-strength materials. Now, thanks to a new understanding of a certain group of spiders, they may soon be easier to work with.
Although most spiders' webs consist of smooth silk threads coated in a sticky natural glue, cribellate spiders do things differently. The threads of their webs are more like a "bristly wool," that actually gets embedded into the bodies of their prey.
As the spiders are making their webs, they excrete thousands of silk nanofibers from their abdomen. Utilizing two rows of specialized rear-leg bristles known as the calamistrum, they grasp those fibers and "comb" them together to form the threads. The spiders themselves don't get caught on those threads as they're making them.
In order to get a better idea of why they don't, an international team of scientists started by shaving the calamistrum off of cribellate "lace weaver" spiders. When they subsequently examined the rear legs of the arachnids after the animals had done some web-building, the researchers noted a buildup of silk nanofibers. This suggested that the calamistrum not only helps comb the fibers, but also prevents them from sticking to the spider.
Additionally, the team found that the surface of each calamistrum bristle was covered in a fingerprint-like pattern of nanoripples. Tests showed that by minimizing the total contact area between the nanofibers and the bristle, those ripples reduced adhesive van der Waals forces, thus keeping the fibers from sticking.
The scientists proceeded to laser-etch similar patterns onto poly(ethylene terephthalate) (PET) foils, which they then coated with a thin layer of gold. When those foils were subsequently pressed against spider silk, they resisted sticking almost as effectively as an actual calamistrum.
It is now hoped that the technology could be put to use in tools that would allow for the simpler and easier handling of human-made nanofibers, making them more practical for widespread use.
A paper on the research, which was led by Dr. Anna-Christin Joel of Germany's Aachen University, was recently published in the journal ACS Applied Nano Materials.
Source: American Chemical Society via EurekAlert