Nanofibre production in spiders without electric charge

Abstract

Technical nanofibre production is linked to high voltage, because nanofibres are typically produced by electrospinning. In contrast, spiders have evolved a way to produce nanofibres without high voltage. These spiders are called cribellate spiders and produce nanofibres within their capture thread production. It is suggested that their nanofibres become frictionally charged when brushed over a continuous area on the calamistrum, a comb-like structure at the metatarsus of the fourth leg. Although there are indications that electrostatic charges are involved in the formation of the thread structure, final proof is missing. We proposed three requirements to validate this hypothesis: (1) the removal of any charge during or after thread production has an influence on the structure of the thread; (2) the characteristic structure of the thread can be regenerated by charging; and (3) the thread is attracted to or repelled from differently charged objects. None of these three requirements were proven true. Furthermore, mathematical calculations reveal that even at low charges, the calculated structural assembly of the thread does not match the observed reality. Electrostatic forces are therefore not involved in the production of cribellate capture threads.

Silk physico-chemical variability and mechanical robustness facilitates intercontinental invasibility of a spider

“…They are distinguishable by their flat, relatively large sheet webs containing dense, irregular lines of cribellate (i.e. lacking glue) capture silk 13 , which they often build on vegetation and urban structures (see photographs in Framenau et al . 12 ; Pompozzi et al .…”

Functional trade-offs in cribellate silk mediated by spinning behavior

“…The reserve warps usually coil into a unique spiral morphology that is thought to enhance extensibility 6,11 . In a classic cribellate thread the nanofibers are combed into characteristic puffs using the calamistrum 5,12 . Removing the calamistrum does not hinder uloborid spiders from using their hind legs to manipulate and produce functional threads, but greatly reduces cribellar puffs, indicating that combing is a crucial stereotyped behavior in cribellate spiders 13 .…”

Wetting and supercontraction properties of spider-based nanofibers

“…Spider dragline silk has been fascinating human-being for thousands of years due to its excellent mechanical properties [1][2][3][4][5][6][7][8][9][10][11][12], and it is a source for biomaterials [13][14][15][16] for tissue engineering applications [17][18][19], and many methods have been proposed to produce artificial fibers mimicking the natural silks [20,21]. The classical approach is to use spider silk proteins to fabricate nanofibers by the electrospinning, though some properties can be enhanced, but it is far behind the natural silks.…”