Literature Review for Micropumps
A survey through the literature reveals that one of the very first documented reports of the concept of a micropump (or miniaturized pump to be exact) can be found in  in 1975. In the patent, the proposed miniaturized pump, which was designed for implantation into the human body, consists of a variable volume chamber bounded by two apposed piezoelectric disk benders, forming a bellows, connected to a solenoid valve (Fig.1). The pump is driven by a rectangular wave pulse generator coupled with a transformer for high voltage amplification. As illustrated in Fig. 1-1(a), in response to a pulse of one polarity (positive), the solenoid valve is activated to retract the plunger against the spring to open the outlet and close the inlet. At the same time, the variable volume chamber begins to expel some of its contents because the voltage induced in the secondary of the transformer causes the disk benders to flex inward. With reference to Fig. 1-1(b), the current flow from the pulse generator stops suddenly at the end of the rectangular wave pulse. This deactivates the solenoid and allows the spring to return the armature to its extended position thus opening the inlet and closing the outlet. In addition, this sudden cessation of current flow through the primary of the transformer induces a large voltage in the secondary which now has a polarity opposite to that of the preceding half cycle. This causes the disk benders to flex in the opposite direction (outward) so that fluid is drawn into the variable volume chamber from the reservoir.
KeywordsShape Memory Alloy Electrostatic Actuation Pump Chamber Pump Membrane Piezoelectric Disc
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