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

Microfabrication techniques have become increasingly popular in the development of the next generation of DNA analysis systems. While significant progress has been reported by many researchers, complete microfabricated integrated DNA analysis devices are still in the earliest stages of development. Most miniaturized analysis systems have incorporated noncross‐linked polymer solutions as the separation medium of choice and the operation of these systems necessitates the use of high electric fields and long separation lengths. 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’ systems. We present the use of photodefinable polyacrylamide gels as a sieving medium for DNA electrophoresis. These gels offer the significant advantages of faster curing times, locally controlled gel interface, and simpler handling over chemically polymerized gels. We also introduce an electrode‐defined sample compaction and injection technique. This technique helps achieve sample compaction without migration into the gel and offers significant control over the size and application of the sample plug. The use of these technologies for double‐stranded DNA separations in microfabricated separation systems is demonstrated.