We investigated the adsorption of Taq enzyme, using sessile droplets, on different microfluidic materials. In propagating adsorption materials, the contact angle (CA) of a sessile Taq droplet continually recedes and collapses due to adsorption. Contrastingly, in contained adsorption materials it exhibits an initial reduced CA due to an instantaneous adsorption, however remains timeinvariant. Spectrophotometer analysis on SU8, a propagating adsorption material, reveals a gradual loss of Taq from the droplet onto the surface during droplet collapsing, as opposed to a rapid saturated adsorption in Teflon, a contained adsorption material. AFM micrographs of the adsorbed surfaces suggest a network-like structure in SU8 and distinctly different pillar-like structures in Teflon. With this understanding, we have successfully applied a SU8-Teflon coating to impart a time-invariant contact angle with minimal loss of Taq in surface microfluidic devices.

Integrated PCR-CE chip technology has immense potential to be applied in clinical diagnostics. In this work we demonstrate the application of our integrated PCR-CE chip for the detection of the respiratory pathogen Bordetella pertussis. A series of experiments with varying cell concentrations (200,000-2 cfu) were performed to obtain the analytical detection limits of the chip. We find that the chip technology is well suited for sensitive detection of Bordetella pertussis, using genetic material from less than even 2 cfu. We also utilized an off-chip real-time PCR method to compare and validate our on-chip approach.

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