I-shaped microchannel array chip for parallel electrophoretic analyses.

We demonstrate electrophoresis in I-shaped microchannels with a new design and operation principle. Unlike the conventional T- or cross-shaped microchannels, the simple I-shaped design makes it straightforward to integrate parallel microchannels with electrodes onto a microchip. The operation of the I-shaped microchannels has been enabled by the autonomous solution filling technique, which exploits the high gas solubility in poly(dimethylsiloxane) (PDMS). We fabricated an I-shaped microchannel array (IMA) chip by integrating 12 independent microchannels and 2 electrodes onto a 3 cm x 2 cm area in a PDMS-glass hybrid microchip. For autonomous regulation of stable sample plugs in all the microchannels, we discovered that O2 plasma treatment of the PDMS-made reservoirs is effective. On the IMA chip, size-dependent separation of double-stranded (ds) DNA and sequence-specific separation of single-stranded DNA were achieved. Specifically, 10 fragments in a 100-1000-bp dsDNA ladder were separated using hydroxyethylcellulose as a sieving matrix within a separation length of 2 mm, and polymerase chain reaction products of the wild-type K-ras gene and its point mutant were separated using a probe DNA-poly(dimethylacrylamide) conjugate on the basis of affinity capillary electrophoresis. The IMA chip presented here opens up a new possibility of large-scale integration of microchannels for high-throughput electrophoretic analyses.