Miniature Solid-State Pumps for Biomedicine

We will develop a new kind of pump for biomedicine. The pump is a small, piezoelectric device that has no conventional moving parts and is only a few mm in overall size. Digital electrical pulses produce individual pumping "strokes," and the pump can be operated at up to 20,000 hz. In our prototype, each pulse delivers approximately 51 pl of fluid; modeling studies indicate that larger and smaller volumes can be produced. The combination of miniature size, precise volumetric control, and digital operation make the piezoelectric pump an attractive candidate for many biomedical applications. Pilot studies indicate that the pumps will work in the laboratory, to pump fluids into cells or tissues, and would also work after implantation into body cavities, to pump fluids directly into tissues or organs. The pump design has evolved from the ink-jet technology utilized at MicroFab. These jets consist of an inner glass capillary tube with a precision-formed orifice surrounded by a piezoelectric outer wall that contracts when activated electronically. The present work will (i) characterize the viscous hydrodynamic behavior that underlies the pumping in our devices, (ii) determine optimum pump shapes and surfaces for pumping, and (iii) build and evaluate prototype pumps.