Research Focus

Our understanding of biological systems critically depend on the tools available to analyze biomolecules and sub-cellular biological components. Advances in modern biology generally coincide with breakthroughs in our ability to separate and identify the target biomolecules out of a highly complex intracellular milieu of diverse biomolecules. Our group's research is focused at developing new tools and technologies for biomolecule separation and analysis using advanced microfluidics and nanofluidics. Toward the eventual goal of all-integrated microfluidic biomolecule analysis systems, currently we are focusing on the following two research areas.

1. Biomolecule separation using nanofluidic molecular sieve: Currently, most of biomolecule purification and separation uses random nanoporous materials as molecular sieving matrix. We are developing MEMS(Micro-Electro-Mechanical System)-based nanofluidic molecular sieves that can filter and separate various biomolecules based on their size or charge density. Unlike polymeric gels or nanoporous molecular filters, nanofluidic molecular sieves and filters could be engineered to have precise physical and chemical characteristics, therefore can have higher separation efficiency and selectivity.
    
2. Microfluidic multidimensional separation system: Multidimensional separation processes, such as protein 2-D gel electrophoresis, are required to analyze complex biomolecule samples such as blood serum or cell extract. Conventional multidimensional separation techniques suffers from difficulties in manual coupling between two heterogeneous separation techniques, say isoelectric focusing and SDS-PAGE. We are currently developing microfluidic protein 2D separation devices that can couple both separations seamlessly and efficiently, without the need of manual operation. The possibility of coupling such devices to mass spectrometry is also studied for a streamlined biomolecule analysis and identification.

Selected Publications

J. Han and A. K. Singh (2003) “Chip-based Miniaturization of Isoelectric Focusing and Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis of Proteins,” Electrophoresis, submitted.

J. Han, and H. G. Craighead. (2002), "Characterization and Optimization of an Entropic Trap for DNA Separation," Analytical Chemistry, 74, 394-401.

J. Han, and H. G. Craighead. (2000), "Separation of Long DNA Molecules in a Microfabricated Entropic Trap Array," Science, 288, 1026-1029.

C.-F. Chou, R. H. Austin, O. Bakajin, J. O. Tegenfeldt, J. A. Castelino, S. S. Chan, E. C. Cox, H. G. Craighead, N. Darnton, T. A. J. Duke, J. Han, and S. Turner. (2000), "Sorting biomolecules with microdevices," Electrophoresis, 21(1), 81-90.

J. Han, S. W. Turner, and H. G. Craighead. (1999), "Entropic trapping and escape of long DNA molecules at submicron size constriction," Physical Review Letters, 83, 1688-1691. Also see erratum.

J. Han, and H. G. Craighead. (1999), "Entropic trapping and sieving of long DNA molecules in a nanofluidic channel," Journal of Vacuum Science & Technology, A: Vacuum, Surfaces, and Films, 17, 2142.

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