Electrophoresis in microfabricated devices using photopolymerized polyacrylamide gels and electrode-defined sample injection

Microfabrication techniques have become increasingly popular in the develop ment of the next generation of DNA analysis systems. While significant prog ress has been reported by many researchers, complete microfabricated integr ated DNA analysis devices are still in the earliest stages of development. Most miniaturized analysis systems have incorporated noncross-linked polyme r solutions as the separation medium of choice and the operation of these s ystems necessitates the use of high electric fields and long separation len gths. In this paper, we present two techniques that may help alleviate this problem and accelerate the development of the so-called 'lab-on-a-chip' sy stems. We present the use of photodefinable polyacrylamide gels as a sievin g medium for DNA electrophoresis. These gels offer the significant advantag es of faster curing times, locally controlled gel interface, and simpler ha ndling over chemically polymerized gels. We also introduce an electrode-def ined sample compaction and injection technique. This technique helps achiev e sample compaction without migration into the gel and offers significant c ontrol over the size and application of the sample plug. The use of these t echnologies for double-stranded DNA separations in microfabricated separati on systems is demonstrated.