(316a) The Economical Fabrication of Surface-Directed Microfluidic Platforms and the Characterization of Capillary Dynamics

The field of microfluidics promises the capacity to automate sophisticated laboratory analyses into a platform that can be implemented by a user with minimal analytical experience. Such devices have been successfully developed. However, the fabrication methods traditionally employed to manufacture microfluidic devices are cost ineffective and time intensive. Consequently, current production techniques render exploiting this technology for clinical application problematic. This work describes an alternative fabrication technique to mitigate the aforementioned problems. By patterning hydrophilic regions upon an otherwise hydrophobic substrate, spontaneous capillary pumping of fluids with high surface tension is achieved after bringing opposing patterns within close proximity.

Hydrophilic conduits are patterned with cellulose acetate or silica sol gel on a variety of commodity polymeric substrates. Patterning technologies implemented thus far include thick film printing, pen plotting and ink jet printing. However, optimal patterning technologies are still under current investigation. Successful platforms are fabricated on materials including polypropylene, polystyrene, and polyvinyl acetate-co-vinyl chloride. The microfluidic patterning technology demonstrates the ability to facilitate spontaneous capillary pumping with a high degree of reproducibility. Furthermore, fluids progress throughout the device with a great deal of precision and rapid succession.

In particular, a micro-device is fabricated demonstrating biological catalysis within enzyme doped silica sol gel matrices. The substrate, O-nitrophenyl-β-D-galactopyranoside, is hydrolyzed to O-nitrophenol and D-galactose yielding a distinct visible yellow response within minutes. The demonstration alludes to the efficacy of such a microfluidic fabrication methodology toward developing cost effective ?lab on a chip' type technologies.

In addition to discussing fabrication technology, we present a model describing the fluid transport from a priori principles along with experimental validation. The driving force for fluid transport within the microfluidic platforms is characterized as intrinsically substantial for the surface-directed flow technique. Furthermore, peculiar phenomena arise such as the entrance condition wherein initial velocity becomes unbounded for an infinitesimally small amount of time. Consequently, methods to treat this phenomenon are addressed with sufficient detail.

The results of our study indicate that robust microfluidic platforms can in fact be produced reliably and economically. In addition, the extension of these results suggest that autonomous microscale total analytical systems can be fabricated with limited rigor and mechanical components warranting immediate implementation of clinical applications.