14. Next-Generation DNA Hybridization and Self-Assembly

The new era of nanotechnology presents many challenges and opportunities. One area of considerable challenge is nanofabrication, in particular the development of fabrication technologies that can evolve into viable manufacturing processes. Considerable efforts are being expended to refine classical top-down approaches, such as photolithography, to produce silicon-based electronics with nanometer-scale features. So-called bottom-up or self-assembly processes are also being researched and developed as new ways of producing heterogeneous nanostructures, nanomaterials and nanodevices. It is also hoped that there are novel ways to combine the best aspects of both top-down and bottom-up processes to create a totally unique paradigm change for the integration of heterogeneous molecules and nanocomponents into higher order structures. Over the past decade, sophisticated microelectrode array devices produced by the top-down process (photolithography) have been developed and commercialized for DNA diagnostic genotyping applications. These devices have the ability to produce electric field geometries on their surfaces that allow DNA molecules to be transported to or from any site on the surface of the array. Such devices are also able to assist in the self-assembly (via hybridization) of DNA molecules at specific locations on the array surface. Now a new generation of these microarray devices are available that contain integrated CMOS components within their underlying silicon structure. The integrated CMOS allows more precise control over the voltages and currents sourced to the individual microelectrode sites. While such microelectronic array devices have been used primarily for DNA diagnostic applications, they do have the intrinsic ability to transport almost any type of charged molecule or other entity to or from any site on the surface of the array. These include other molecules with self-assembling properties such as peptides and proteins, as well as nanoparticles, cells and even micron-scale semiconductor components. Microelectronic arrays thus have the potential to be used in a highly parallel electric field “pick and place” fabrication process allowing a variety of molecules and nanostructures to be organized into higher order two- and three-dimensional structures. This truly represents a synergy of combining the best aspects of “top-down” and “bottom-up” technologies into a novel nanomanufacturing process.