Abstract
The rapid squirt of a proteinaceous slime jet endows velvet worms (Onychophora) with a unique mechanism for defence from predators and for capturing prey by entangling them in a disordered web that immobilizes their target. However, to date, neither qualitative nor quantitative descriptions have been provided for this unique adaptation. Here we investigate the fast oscillatory motion of the oral papillae and the exiting liquid jet that oscillates with frequencies f~30–60 Hz. Using anatomical images, high-speed videography, theoretical analysis and a physical simulacrum, we show that this fast oscillatory motion is the result of an elastohydrodynamic instability driven by the interplay between the elasticity of oral papillae and the fast unsteady flow during squirting. Our results demonstrate how passive strategies can be cleverly harnessed by organisms, while suggesting future oscillating microfluidic devices, as well as novel ways for micro and nanofibre production using bioinspired strategies.
Highlights
The rapid squirt of a proteinaceous slime jet endows velvet worms (Onychophora) with a unique mechanism for defence from predators and for capturing prey by entangling them in a disordered web that immobilizes their target
We demonstrate that the fast oscillations of the jet slime and papillae in Onychophora are the result of a syringelike system that, by means of a geometric amplifier, allows for fast squirt using slow muscular contraction
We present a physical simulacrum that reproduces the instability in the same range of parameters of the natural system opening new venues for selfsupported microfluidic devices and applications[19,20,21,22]
Summary
The rapid squirt of a proteinaceous slime jet endows velvet worms (Onychophora) with a unique mechanism for defence from predators and for capturing prey by entangling them in a disordered web that immobilizes their target. We demonstrate that the fast oscillations of the jet slime and papillae in Onychophora are the result of a syringelike system that, by means of a geometric amplifier, allows for fast squirt using slow muscular contraction.
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