Low-cost, polymer microsystems for drug delivery and dosing

This dissertation describes the development of a low-cost, micro-scale drug delivery systems with dosing accuracy down to 1 muL/min. Both fabrication and device design innovations are included.;The feasibility of using polymer injection molding to make microscale parts is demonstrated using analytical methods, numerical models, and experimental results. Micro rods with cross-sections of 140 mum x 200 mum and 100 mum x 140 mum are injection molded out of cyclic olefin copolymer (Topas). Their aspect ratios are greater than 15:1 and 7:1, respectively---a fourfold improvement over previous efforts [60,61,62].;Investment molding, a combination of injection molding and investment casting, is used to create hollow microneedles. Plastic is injection molded around a sacrificial element placed that is etching after molding to create a hollow part. Microneedles with internal diameters of 35 mum are created. Prismatic needle with rectangular cross-section (280 mum long, and 130-160 mum x 100 mum) and a tapered needle with triangular cross-sections (300 mum long and with two 105 mum sides and one 150 mum side) are demonstrated.;A simple microscale, flow sensing method---bubble-time-of-flight---that requires no calibration, is developed. The method measures flow rate by detecting the time required for a bubble to traveling down a microchannel. A device consisting of a micromachined silicon wafer capped with a glass wafer is able to detect bubbles using the thermo-resistive response of two thin film resistor. Fluid flows between 100 muL/min and 1 muL/min are detected with error below 1% at the low-end. Lower flow rates (∼100 nL/min) are also detected but not verified due to the limitations of the test setup.;Low-cost processes are utilized to make the components of the bubble-time-of-flight sensor. Substrates that have the same features as the silicon and glass wafers used in the silicon/glass device are injection molded out of Topas. Metal lift-off is utilized to create gold, thin film resistors on these parts with critical dimensions of at least 30 +/- 1 mum. In addition, shadowmasking, a non-lithographic method, is able to pattern metal to 50 +/- 3 mum. Solvent bonding adheres the two parts together though, the quality of the bond is not sufficient to create a functional device.