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Design and Fabrication of a Ferrofluidic Miniature Pump

Ashouri, Majid | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49019 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad; Moosavi, Ali
  7. Abstract:
  8. This thesis presents the prototype design and fabrication of magnetically actuated miniature pumps which utilize self-sealing capability of ferrofluid-covered permanent magnets in both pumping and valving mechanisms. The contactless external actuation feature of the design enables integration of the pump with other PMMA-based microfluidic systems with low cost and disposability. The body of the 1st fabricated prototype pump consists of three nozzle/diffuser elements and two pumping chambers connected to the ends of a flat-wall pumping cylinder. A cylindrical permanent magnet placed inside the pumping cylinder acts as a piston which reciprocates by using an external magnetic actuator driven by a motor. The magnetic piston is covered by a ferrofluid to provide self-sealing capability. Three-dimensional numerical simulations are also carried out to study the performance of the pump. In the 2nd design, the valving action is performed by employing one active valve along with two nozzle/diffuser elements. Two cylindrical permanent magnets are placed inside the flat-wall channels; one magnet acts as the active valve and the other one serves as a reciprocating piston actuating the working fluid. In order to seal the gaps between the channel walls and the permanent magnet of the valve/piston, ferrofluid is used to cover the surfaces of both magnets. The valve and the piston are actuated using external permanent magnets driven by two separate stepper motors. In the 3rd pump, the minichannel consisting of a cylindrical pumping chamber, a check valve, an inlet and an outlet, comprises six bonded layers of PMMA. A cylindrical permanent magnet that is placed inside the chamber and is externally actuated by a motorized off-center permanent magnet, functions as a revolving piston which sweeps the perimeter of the cylinder. Ferrofluid is used to cover the gaps between the magnetic piston and the channel walls, also serves as a separating plug between the inlet and the outlet of the chamber preventing recirculation of the pumped fluid inside the chamber. This novel revolving piston design eliminates the need for an inlet valve. Pressure head is maintained using one ball check valve at the outlet of the pump. With total volume of about 6 cm3, the pumps are capable of pumping the water at flow rates of up to 1000 µL/min and backpressures of up to 1 kPa
  9. Keywords:
  10. Micropumps ; Ferrofluid ; Microchannel ; Microvalve ; Magnetic Actuation

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