Osmotic Phenomena
Osmosis refers to general phenomena in mechanical systems where pressures and forces are generated in a fluid or gas solvent by solute particles which are confined by semi-permeable membrane boundaries or electric fields. Such forces and pressures play a fundamental role in many biological systems and technological devices. Some examples in biology include mechanisms responsible for exchange of nutrients and wastes in microscopic capillaries in tissues and means of propulsion in cell motility. In technological applications, microscopic devices have been designed which utilize osmotic effects to pump fluids or utilize osmotic effects to actuate forces via swelling. The classical theories for osmotic pressure, such as van't Hoff's relation, become inaccurate for microscopic systems where solute particles interact on length scales comparable to the size of the confining chamber. Classical theories of osmosis also typically assume systems are in thermodynamic equilibrium.
To study systems in regimes applicable to biological systems and microscopic devices we are developing theory to describe microscopic osmotic phenomena both in equilibrium and non-equlibrium settings. Some recent work includes studying how osmotic pressures generated by polymer solutes depend on polymer topology, stiffness, and excluded volume. In related work, a pumping mechanism for a microfluidic device has been proposed which uses reversible chemical reactions to drive fluid flows.
Select Publications
- A Microfluidic Pumping Mechanism Driven by Non-equilibrium Osmotic Effects, Atzberger, P.J., Isaacson, S.A., and Peskin, C.S., Physica D: Nonlinear Phenomena, Vol. 238, Iss. 14, July, pp. 1168-1179, (2009),[PDF] [DOI]
- Theoretical Framework for Microscopic Osmotic Phenomena, Atzberger, P.J. and Kramer, P.R. , Phys. Rev. E, 75, 1, (2007). PDF] [DOI]