| The field of microfluidics has the potential to revolutionize the analysis of chemical and biological systems by rapidly testing small quantities of materials in inexpensive devices. One advantage of microfluidics that has not been extensively investigated is the potential portability of these lab-on-a-chip systems. The goals of this dissertation are to understand flow control elements for portable microfluidic applications and develop a fabrication method to construct disposable, polymeric microdevices.; To construct these flow control elements, a novel fabrication method, Contact Liquid Photolithographic Polymerization (CLiPP), is presented to fabricate rapidly complex, three-dimensional polymeric microdevices using a variety of materials. By adding photoiniferter molecules in the monomer formulations, covalent bonding occurs between the multiplicity of materials and layers within the microdevice. In addition, the photoiniferter molecules enable grafting from the polymer to control the surface chemistry of the channels.; Three micropumping systems are developed and characterized to function over a wide range of fluid flow rates (0.1--1000 muL/min) with the aid of little to no external power. The operating principle to actuate each micropump is different. One micropump utilizes the swelling of fluid-responsive polymer particles to displace fluid, while the other two micropumps use gas, generated from either an effervescent reaction or the electrolysis of water, to transport liquid. Each micropump is directly integrated in a microfluidic device and evaluated for ease of fabrication. Models are developed to describe the micropumps and show good agreement with experimental results. These models are then used to investigate methods of controlling fluid flow rates.; In addition to investigating portable micropumps, other flow control elements, such as valves, mixers, and resistant heaters, are examined for field-use microfluidic applications. Variables pertaining to the formation of low-modulus polymers, porous polymer networks, and conductive pastes are analyzed to determine their impact in these unit operations. |
