An adaptable microvalving system for on-chip polymerase chain reactions.

On-chip genetic analysis systems are beginning to provide a viable alternative to conventional gene profiling and amplification devices, through minimal reagent use, high detection resolution, and the potential for high-throughput parallel testing of the genetic material, even from single cells. Despite the advantages, there are many difficulties inherent in creating an integrated microfluidic diagnostic platform. One major challenge is the accurate control and manipulation of fluid, and particularly the immobilization of reaction mixtures during heating phases of polymerase chain reactions (PCR). In this paper we present a pumping and valving system based on the use of three servomotor-controlled valve fingers that actuate microchannels within a poly-dimethylsiloxane (PDMS) fluidic chip. We characterize the valving ability of the system in terms of fluid loss and show the successful fluid retention of the system over 35-cycle PCR runs at temperatures of up to approximately 96 degrees C. In addition, we demonstrate the system's ability to perform PCR by successfully amplifying a sample of beta2 microglobulin transcript obtained from the peripheral blood of a patient with multiple myeloma. This work has proven to be a successful approach to multi-use valving and a viable method of alleviating the fluid control difficulties inherent in performing a PCR reaction in an on-chip environment. In addition, it opens the door for further automation and integration with other chip-based genetic analysis platforms.