Mimicking nonstick spiders

Spiders are giving humans a hand (rather, a leg) when geckos get us into sticky situations. Researchers have long known that engineered micro- and nanostructures that mimic gecko feet can make surfaces supersticky. But what to do when surfaces shouldn’t stick to something, say tools or processing equipment? Anna-Christin Joel of Aachen University realized that cribellate spiders have a solution to this problem. The webs of these spiders derive their stickiness from structure—a wool-like coating of silk nanofibers—rather than protein glues. Tiny comb-like structures called calamistra on the spiders’ legs are able to fluff up this silk without sticking to it.

Working with Werner Baumgartner of Johannes Kepler University Linz, Joel and her team showed that the geometry of calamistrum ripples (shown) minimize van der Waals interactions and, thus, adhesion with the nanofibrous silk. The team took this information a step further, using laser light to create ridges in polymer films to emulate calamistra. They showed that modified films adhered less to cribellate spider silk than the native polymer (ACS Appl. Nano Mater.2020, DOI: 10.1021/acsanm.0c00130). Such surfaces could be useful for handling and processing electrospun nanofibrous threads employed in filtration, Joel says.