Biological fluid mechanics

Scanning electron microscope images of the integument of the water-walking insect Mesovelia. The rough, waxy hairs support a plastron air bubble, which allows the insect to breathe while submerged underwater. Respiration occurs through spiracles, an example of which is shown in (d). (Photo credit: M. Prakash).


An idealized model of an insect's hair mat showing the characteristic "L" shaped hairs (from Flynn & Bush, J. Fluid Mech. in-press).


The air-water interface. The plastron surface has negative curvature and the air bubble is consequently sub-atmospheric in many cases of biological relevance (from Flynn & Bush, J. Fluid Mech. in-press).


The rough, waxy exterior surface of many insects and spiders confers water-repellent properties that allow arthropods to walk on water, survive accidental collision with rain drops and even breathe while submerged. In the latter case, respiration occurs via a "plastron" air bubble, across whose surface there is an exchange of oxygen and carbon dioxide. Working with John W. M. Bush (MIT), I have, by way of theoretical modeling, examined circumstances in which the respiratory function of the plastron is particularly advanced, such that arthropods may remain below the water surface indefinitely. As indicated by the following reprint, this analysis combines biology, surface and gas-phase chemistry as well as interfacial mechanics and may have important biomimetic applications.

I am also interested in seed dispersal from germinating flowers, work conducted with the thoughtful assistance of Steve Vogel (Duke Univ.) and also pattern formation in migrating herds, work conducted with a number of colleagues from MIT and the Technical Univ. of Catalonia.

Movies:
Boatman grooming him/herself. Such grooming behavior is thought to increase the area of the insect's plastron, the silvery air bubble located along the abdomen. (Movie credit: J. W. M. Bush)

Recent publications:
Breathing underwater: the mechanics of plastron respiration ( J. Fluid Mech. in-press, with J. W. M. Bush) (.pdf)