National Center for Design of
Biomimetic Nanoconductors

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Narayan Aluru

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Narayan Aluru is an associate professor in the UIUC Mechanical & Industrial Engineering and a full-time faculty member in the Beckman Institute for Advanced Science and Technology. His research interests span computational methods for applications in microelectromechanical systems (MEMS), nanoelectromechanical systems (NEMS), micro and nanofluidics and bionanotechnology. He is currently funded on projects focusing on the development of efficient computational methods for multiphysics analysis of MEMS, physical models and multiscale theories for analysis of MEMS, liquid and gas transport through microscale channels, and investigation of fundamental issues in nanofluidics.

Research

Aluru’s nanofluidics research is most closely related to the Center goals. His group has performed in-depth studies on the transport of water and electrolytes in confined nanochannels. First, they have performed detailed comparisons on ion concentrations and velocity profiles obtained from molecular dynamics (MD) and continuum theory. Their results (Qiao et al., 2003) indicate that the finite size of the ions and the discreteness of the water molecules – that are neglected in the continuum theory – play an important role. To account for the molecular effects, they have extended the classical continuum theory for ion concentrations by developing a modified Poisson-Boltzmann equation using the concept of electrochemical potential correction. To compute the electrochemical potential correction, they have introduced an embedding multiscale method. They have also extended the embedding multiscale method to compute the velocity profiles accurately in nanochannels (Qiao et al., 2004). The key idea in the embedding multiscale method is to resolve the interfacial layer, where molecular effects are dominant, by MD simulations and to incorporate the MD results into the continuum theory.

Second, Aluru’s group has reported charge inversion and flow reversal in nanochannel electroosmotic flows (Qiao et al., 2004). Specifically, they have shown that for a large surface-charge density and concentration of the electrolyte, the concentration of the co-ions in the interfacial layer can exceed the concentration of the counter-ions (classical text books predict that the concentration of the counter-ions is always larger than the concentration of the co-ions). This is referred to as charge inversion. An important consequence of charge inversion is flow reversal. As the electroosmotic force is proportional to the difference between the counter-ion and co-ion concentrations, when charge inversion occurs, the electroosmotic force changes direction and causes flow reversal.

Third, the group has reported that the water flux and the ionic conductivity through two oppositely charged nanochannels, that are otherwise similar, differ by a factor of more than three and the co-ion fluxes are in the opposite direction. Such a behavior cannot be predicted by the classical transport theory and they have shown that the asymmetry originates from the different properties of water and ions in the interfacial layer (Qiao et al., 2005).

Fourth, they have also investigated water and ion transport through carbon nanotubes (CNTs) and have shown that confinement can induce anomalous immobilization of water in CNTs (Mashl et al., 2003). They have also reported that functionalized CNTs can be used to mimic some of the properties of biological ion channels (Joseph et al., 2003).

Finally, Aluru’s group has used their models and simulation tools to compare with experimental data on ion transport through molecular gates and silicon nitride nanochannels. In collaboration with Prof. Paul Bohn (Chemistry, UIUC), they have shown that their models can be used to predict current-voltage and current-time characteristics in molecular gates. In collaboration with Prof. Greg Timp (ECE, UIUC), they have shown that their combined MD and continuum approach can be used to predict conductivity in silicon nitride nanopores. 

Within the Center, there will be a strong direct connection between Aluru’s theoretical work and Brinker’s experimental work on chemically decorated nanopores.

Related Publications

J. Mashl, R., S. Joseph, N. R. Aluru, and E. Jakobsson. "Anomalously Imobilized Water: A New Water Phase Induced by Confinement in Nanotubes," Nano Letters, 3:5, 589-592, 2003.

Joseph, S., R. J. Mashl, E. Jakobsson and N. R. Aluru. "Electrolytic Ttransport in Modified Carbon Nanotubes," Nano Letters, 3:10, 1399-1403, 2003.

Qiao, R. and N. R. Aluru. "Scaling of Electrokinetic Transport in Nanometer Channel," Langmuir, 21:19, 8972-8977, 2005.

Qiao, R. and N. R. Aluru. "Surface-Charge-Induced Asymmetric Electrokinetic Transport in Confined Silicon Nanochannels," Applied Physics Letters, 86, 14--143105, 2005.

Chatterjee, A. N. and N. R. Aluru. "Combined Circuit/device Modeling and Simulation of Integrated Microfluidic System," Journal of Microelectromechanical Systems, 14:1, 81-95, 2005.

Chatterjee, A. N., D. M. Cannon, E. N. Gatimu, J. V. Sweedler, N. R. Aluru and P. W. Bohn. "Modeling and Simulation of Ionic Currents in Three-Dimensional Microfluidic Devices with Nanofluidic Interconnect," Journal of Nanoparticle Research, 7:4-5, 507-516, 2005.

R. Qiao and N. R. Aluru, ``Ion concentrations and velocity profiles in nanochannel electroosmotic flows'', Journal of Chemical Physics, Vol. 118, No. 10, pp. 4692-4701, 2003.

R. Qiao and N. R. Aluru, ``Charge inversion and flow reversal in a nanochannel electro-osmotic flow'', Physical Review Letters, Vol. 92, No. 19, Art. No. 198301, 14 May 2004.

Related Links

Comprehensive List of Publications

Narayan Aluru's Beckman Institute Profile

Narayan Aluru's Mechanical and Industrial Engineering Profile

The National Center for Design of Biomimetic Nanoconductors is funded by Grant Number PHS 2 PN2 EY016570B from the National Institutes of Health through the NIH Roadmap for Medical Research and is based at the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign. Partner institutions include University of Chicago, Illinois Institute of Technology, Sandia National Laboratories, Wabash College, University of California, Davis, and the University of New Mexico, University of Illinois at Chicago, Weill Cornell Medical College, and the National Institute of Standards and Technology.