| This dissertation presents advancements in the field of polymeric microfluidic devices, both in terms of fabrication and application, with the utilization of a new material and development of the associated fabrication techniques, as well as the application of polymeric microfluidic devices to droplet applications.; Through a progression of development phases, thermoset polyester (TPE) was determined to be suitable for the fabrication of microfluidic devices. TPE can be replica molded against photolithographically patterned silicon masters. Masters were pretreated with hexamethyldisilazane to prevent adhesion of TPE and ensure high quality replication of features, reproducing fairly complex and multilayer features with dimensions as small as a few mum. Curing of TPE devices was accomplished in less than three hours, through the use of a combination of ultraviolet and thermal initiators, resulting in rigid, nonelastomeric final devices. For applications requiring devices with short working distances, such as in the use of high numerical aperture objectives for fluorescence imaging or optical trapping, a thin (∼100 mum) layer of TPE can be fabricated. TPE can also be sealed to glass substrates following exposure to oxygen plasma. The surface properties of TPE were characterized, and TPE was shown to support electroosmotic flow (EOF) toward the cathode that was stable for days using electric fileds up to 600 V/cm. TPE devices also exhibited excellent optical transparency to visible light and were shown to be compatible to a wide range of solvents, including nonpolar solvents.; Finally, an approach for the simultaneous generation of multiple droplets in a poly(dimethylsiloxane) device is described. Small nozzles, with a cross-section of 7 mum by 7 mum, were fabricated at the outlets of a microfluidic gradient generator design, separating the aqueous phase output channels from a large channel containing the oil phase. By controlling the oil phase flow in a pulsitile manner, droplets were simultaneously generated at multiple nozzles. |
