The design and development of an electromagnetically actuated nozzle/diffuser micropump

This research presents the design and development of a magnetically actuated nozzle/diffuser micropump for use in the treatment of glaucoma. The micropump is composed of a cast poly(dimethylsiloxane) (PDMS) body containing all fluidic features, a spin coated PDMS membrane for sealing the fluidic features, and commercial silicone tubing for an inlet and an outlet. All components of the micropump are sealed together using only PDMS. The micropump has a final thickness of approximately 1mm due to a novel in-plane inlet and outlet tube attachment method, is flexible due to an all PDMS construction, easily fabricated due to a simple fabrication procedure, and is made of materials which show evidence of good biocompatibility. The pump is wirelessly actuated using a solenoid actuator and a small magnetic or ferromagnetic object placed on the surface of the PDMS membrane. The geometry of the solenoid has been optimized to produce the greatest magnetic field strength. Research work also involved the characterization of the thickness and Young's Modulus of PDMS and iron-PDMS composite membranes. Various pumps were fabricated and tested. For the most successful design, a peak flow rate of 135.0muL/min and a maximum back pressure of 25mmH2O were obtained using an actuation frequency of 12Hz, duty cycle of 25%, and a 4-40 low strength steel nut for membrane actuation. Results show that increasing the membrane thickness, using the most strongly attracted membrane actuator, and using a 50% actuation duty cycle increases micropump performance. The results also suggest that using a magnetic material as opposed to a ferromagnetic material would allow for the membrane actuator to be reduced in size. The peak flow rate of the micropump is significantly greater than the rate of aqueous humor production (2.8 +/- 0.8muL/min), meaning that the performance of the micropump is sufficient for the intended application.