Page 241 - Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim

APPLICATIONS 221

Polyimide
diaphragm Adhesive

Pump case Heater Actuator
chamber
shells of PSU

(j> 0.95 mrn t 03.8mm f I I 0 0.96 mm Valve
Valve // Inlet valve ~", , * i I " T , , seat
orifice
4> 150 urn

Figure 7.64 Micropump fabricated in a small-scale production line. From Schomburg et al. (1998)

250

200-

^ 150

100-

50-
5 Hz
1 I
20 40 60 80 100 120
Pressure generated at outlet (hPa)
Figure 7.65 Typical flow rate as a function of the micropump pressure at various driving
frequencies

(Jiang et al. 1998). This states that

Q oc rj&Vf a r]fwA (7.16)

where n is a coefficient relating to the valve leakage or efficiency, f is the actuating
frequency, AV is the difference in volume between the pump mode and the supply
mode, and is proportional to wA, where A is the diaphragm area within the pump
chamber.
The deflection of the actuation diaphragm in a micropump fabricated by AMANDA
process can be one-to-two orders of magnitude higher than that of the silicon micropump.
Also, the excellent conformity of the valve membrane leads to a high efficiency n.
All these characteristics are associated with a high output flow rate and back pres-
sure (Figure 7.65). However, the working frequency of this micropump is relatively low