49. Manipulation of Single DNA Molecules by Induced-Dipole Forces in Micro-Fabricated Structures 

Chip Asbury, Paolo Prati, and Ger van den Engh 
Department of Molecular Biotechnology, University of Washington, WA 98195 
asbury@biotech.washington.edu 

We are exploring the use of induced-dipole forces in oscillating, divergent electric fields, for trapping, moving and stretching DNA molecules. These forces, which are distinct from electrophoretic forces, can be generated by means of microscopic metal patterns on quartz substrates. Micro-fabrication techniques can be employed to generate large numbers of traps on a single wafer. This technology lends itself well for massive automation and parallelization of DNA sample preparation. 

Unlike electrodes for electrophoresis, DNA trapping can be achieved with floating electrodes. Voltage applied by external wires to the fluid is passively distributed among hundreds of microelectrodes. The electric field lines concentrate on the electrode edges exerting strong attractive forces on DNA molecules in solution. If the electrode gaps are small, significant trapping forces can be obtained without inducing electrolysis. The magnitude of these forces appears to vary with DNA molecular weight. 

We have built several devices for manipulating small quantities of DNA, such as shift registers, DNA concentrators, etc.. We are now developing more complex structures that combine DNA dipole traps with more elaborate manipulations. We have made electrophoresis capillaries with concentrating traps at the entrance and exit. We have constructed capillaries with a series of traps along their length for size dependent DNA separation. We are working on a device that guides DNA molecules along a precise trajectory past a fluorescence detector. We are also exploring the use of traveling waves to concentrate DNA from a large area. 

We will describe these and other structures and will present the conditions under which these devices are most efficiently used.