Biomedical Engineering Reference
In-Depth Information
The number of orifi ces is dependent on the number of grooves. The back of the grooves
is then sealed with an acoustic energy absorbing polymer. Figure 11.4 shows the com-
plete printhead fabrication process.
When the grooves are formed by sawing the channels in the piezoelectric mate-
rial rectangular block, the walls are formed into actuators as well. The voltage applied
through the walls causes an electric current to fl ow through. The electric current is trans-
formed into a mechanical moving force to drive a small amount of droplets from the fl uid
channel out of the orifi ce. The mechanical motion is shown in Fig. 11.5. The amount of
current will determine the size of the droplets. This droplet is then dispensed from the
printhead. Table 11.3 shows some of the data obtained from the inkjet printing method.
Any forms of contamination at the orifi ce will lead to the misdirection of the drop-
lets; hence, the inkjet printing method requires that the orifi ce be free of contaminations.
Damages at the orifi ce must be repaired in order to prevent the altering of the size of the
Polyimide orifice plate
Fluid manifold
Cover plate
Bond pad for
flex circut
Thin PZT
Orifice
Seal
Bottom PZT
FIGURE 11.4
Printhead with cover, orifi ce plate and channel sealing.
Cover plate
Electric field
Voltage
Voltage
PZT
Polling
direction
FIGURE 11.5
Mechanical motion of the actuator.
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