Dynamics of biofluids

orientationalorderActive hydrodynamics

Swimming bacteria and cellular membranes are examples of soft materials that inhabit an environment that involves mechanical and chemical stimuli on a regular basis. The ability to respond to mechanical impulses and hydrodynamics of an viscous medium enable micro-organisms to swim and communicate, and these same forces facilitate the transport of proteins and nutrients throughout cells.

Studying these systems requires an understanding of the interplay between elasticity and fluid mechanics, as well as the forces provided by internal sources of chemical energy that generally power micro-organisms and nanoscopic machines.

Stokesian jellyfish: Viscous locomotion of bilayer vesicles
A. A. Evans, S. E. Spagnolie, and E. Lauga
Soft Matter 1737-1747 (2010)

Fluid transport by active elastic membranes
A. A. Evans and E. Lauga
Phys. Rev. E 84 031924 (2011)

Confinement effects on swimming organisms:

It is rare to find organisms swimming entirely unimpeded by neighbors or boundaries, and the effects of walls and other swimmers has drastic consequences for the trajectories and behavior of many kinds of creatures.

Orientational order in concentrated suspensions of spherical microswimmers
A. A. Evans, T. Ishikawa, T. Yamaguchi, and E. Lauga
Phys. Fluids 23 111702 (2011)

Propulsion by passive filaments and active flagella near boundaries
A. A. Evans and E. Lauga
Phys. Rev. E 82 041915 (2010)

Measuring mechanical properties of biomembranes:

The materials that coat the surfaces of our lungs are notoriously fragile substances, but understanding how these monolayers of surfactant flow and respond to external stimuli is vital to learning how these fluids function. Similarly, cellular membranes are partially composed of a bilayer of the same molecules, usually some kind of phospholipid, whose structure and function depend on the flow and elastic properties of the crosslinking proteins and embedded macromolecules. Probing the viscoelasticity of these materials tricky, since conventional rheological techniques may be destructive to the sample, or misrepresent the material response entirely. New methods are emerging using non-contact or submerged particle interfacial microrheology (or SPIM) which may be used to determine the rheological characteristics of fragile materials, and elevate our understanding of hydrodynamics near complex interfaces.

swimmem

Measurement of Monolayer Viscosity Using Non-Contact Microrheology
R. Shlomovitz, A. A. Evans, T. Boatwright, M. Dennin, and A. J. Levine
Phys. Rev. Lett. 110 137805 (2013)

Probing interfacial dynamics and mechanics using submerged particle microrheology I: theory
R. Shlomovitz, A. A. Evans, T. Boatwright, M. Dennin, and A. J. Levine
Phys. Fluids 26 071903 (2014)

Probing interfacial dynamics and mechanics using submerged particle microrheology II: experiment
T. Boatwright, M. Dennin, R. Shlomovitz, A. A. Evans, and A. J. Levine
Phys. Fluids 26 071904 (2014)

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