Molecular understanding of osmosis and a multiscale framework to investigate confined fluid properties

Understanding the fluid structure and behavior in nanoscale confinements is of major importance in a wide variety of applications including biological and engineering devices. A critical biological application in which the physics at the nanoscale is important is osmosis. Critical functions of life as well as technology to develop better water filtration systems depends on a fundamental understanding of osmosis. In this thesis, first, a molecular understanding of osmosis in uncharged and charged semi-permeable membranes is developed using Molecular Dynamics (MD) simulation studies. Specifically, we identify key inter-molecular forces that initiate osmosis in uncharged and charged membranes and explain the significance of various inter-molecular forces as the system evolves to a steady-state. We also investigate the effect of size-asymmetric electrolytes on osmosis through uncharged semi-permeable membranes. Second, we develop a multiscale framework to investigate fluids in confinement. Since the atomistic simulations are extremely computational, they become intractable at very large length scales. Also, the classical continuum theory breaks down at the atomistic level. Towards the goals of bridging the two scales, we formulate a semi-classical framework to predict the concentration and potential profiles of LJ fluids confined in channels of widths ranging from 2 sigma to 100 sigma (sigma is the fluid-fluid LJ parameter). The semi-classical framework utilizes the Nernst-Planck equation coupled with a theoretical potential formulation to obtain the accurate concentration and potential profiles in a channel. The results obtained from the semi-classical framework are then compared with results obtained from MD simulations in the channel.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2010

Author dc:creator

• Raghunathan, Anjan V.

Contributors dc:contributor

• Aluru, Narayana R.
• Georgiadis, John G.
• Ravaioli, Umberto
• Tajkhorshid, Emad

• Multiscale simulations
• Nanofluidics
• Osmosis

Statement dc:rights

• Copyright 2010 Anjan V Raghunathan

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/15563

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/15563