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MSE Seminar Series: Paula Mellado
Friday, March 13, 2015
1:00 p.m.-2:00 p.m.
Room 2110, Chemical and Nuclear Engineering Bldg.
For More Information:
JoAnne Kagle
301 405 5240
jkagle@umd.edu

Bio-inspired microfluidics: The case of the velvet worm

Paula Mellado
School of Engineering and Sciences
Adolfo Ibañez University, Santiago, Chile

The rapid squirt of a proteinaceous slime jet endows the ancient velvet worms (Onychophora) with a unique mechanism for defense from predators and for capturing prey [1–6] 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 [1, 2, 7, 8]. We have investigated the mechanism that allows velvet worms the fast oscillatory motion of their oral papillae and the exiting liquid jet that oscillates with frequencies ƒ ~ 30 – 60  Hz. Using anatomical images and high speed videography, we show that even without fast muscular action of the papilla, a strong contraction of the slime reservoir and the geometry of the reservoir-papilla system suffices to accelerate the slime to speeds up to ν ~ 5  m/s in about  ∆t ~ 60  ms. A theoretical analysis and a physical simulacrum allow us to infer 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. Inspired by the physics of the velvet worm squirting system we propose several applications that can be implemented using this instability. Ranging from high-throughput droplet production, printing, micro-nanofiber production between others [9] .

[1] Belt, T. The naturalist in Nicaragua: A narrative of a residence at the gold mines of Chontales; journeys in the savannahs and forests; with observations on animals and plants in reference to the theory of evolution of living forms, vol. 561 (ICON Group International, 1888).

[2] Bouvier, E. Monographie des Onychophores, vol. I (Masson et Cie., 1905).

[3] Claude-Joseph. Sur un peripate du chili. Annales des Sciences Naturelles, Zoologie et Biologie Animale (Serie 10), 285-299 (1928).

[4] Alexander, A. Notes on onychophoran behavior. Annals of the Natal Museum 14, 35-43 (1957).

[5] Alexander, A. Peripatus: _erce little giant. Annals of the Natal Museum 14, 35{43 (1958).

[6] Read, V. & Hughes, R. Feeding behaviour and prey choice in macroperipatus torquatus (onychophora). Proceedings of the Royal society of London. Series B. Biological sciences 230, 483-506 (1987).

[7] Morera-Brenes, B. & Monge-N_ajera, J. A new giant species of placented worm and the mechanism by which onychophorans weave their nets (onychophora: Peripatidae). Revista de biolog–a tropical 58, 1127-1142 (2010).

[8] Haritos, V. et al. Harnessing disorder: onychophorans use highly unstructured proteins, not silks, for prey capture. Proceedings of the Royal Society B: Biological Sciences 277, 3255-3263 (2010).

[9] Kang, E. et al. Digitally tunable physicochemical coding of material composition and topography in continuous micro_bres. Nature Materials 10, 877-883 (2011).

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