Page 242 - Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim

222 MICROSTEREOLITHOGRAPHY FOR MEMS

because thermal pneumatic actuation was adopted, which may not be acceptable in some
applications requiring high flow uniformity. The technical data of this type of micropump
are listed in Table 7.1. It should be noted that both the housings and the diaphragms of the
micropump are made of polymer and can be selected according to the special demands of
the particular application, for example, biomedical fluid delivery. Another advantage of
AMANDA is that it is a batch-fabrication process and therefore enables the production
of a micropump at a relatively low cost.
Several types of microvalves have been developed with AMANDA (Schomburg et al.
1998). For example, a bistable microvalve, which consists of a preformed polyimide
membrane that is able to occupy two stable positions (Figure 7.66). In the top position,
the membrane closes the inlet duct of the fluid chamber, whereas, in the bottom position
it clears that opening. In this case, the valve is controlled pneumatically. The technical

Table 7.1 Technical specification of a micropump. From Insti-
tute for Mikro
Pump attributes: Values
Dimensions of the pump (mm) 9.3 x 10 x 1.2
Maximum height with fluidic ports (mm) 7.9
Outer diameter of fluidic ports (mm) 0.91
Flow rate without back pressure (^il/min) 150-250
Maximum pressure generated (hPa) 70–120
Life under laboratory conditions (load cycles) >315 million
Drive voltage (V) 10-15
Drive pulse width (ms) 1–2
Drive frequency (Hz) 5-30
Power consumption (mW) ~ 150
Pump case Polysulfone
Pump membrane Polyimide
Adhesive bonds Epoxy resin
Heater coil Gold
Fluidic connection tube Stainless steel
Note: Values for operation at 22 °C.

Figure 7.66 Cross section of a bistable micropump (top) and a bistable microvalve (bottom)