2. Actuators
Actuator principles
Electro-statics actuators : with a spring and electrodes , force created with electrical field
++ Accuracy, little wear, low power, good integration
— : high operating voltages, non linear, electric break-down
microvalve
! Think about surface forces which may be big and connect materials together
Piezo-electric actuators
Applying voltage create deformation
Typically Quartz or Lead-Zircon-Titanate
++: large force possible, geometric variety
— : very high voltage, very small displacement, strong heating, drift
micropump
Shape-memory alloy
Different crystal phase between martensite and austenite state
Martensite state can be easily deformed, when heated to austenite → go back to original state
Example: pass electrical current to heat and go back to original shape
++: large displacement and forces, simple principle, abrasion free
—: poor efficiency, poor dynamics, heat dissipation problem
valve, microgripper
Electro-magnetics actuators
large compared to other technics !
++ High efficiency, low voltage, large travel ranges
—: high current, heat dissipation, integration problematic
The coanda-effect
A gas jet or liquid tends to flow along a convex surface (toggle effect can be used)
toggle valve