Biomedical Engineering Reference
In-Depth Information
Skin
Suction
Pushing
(a)
(b)
Figure 7.12
We feel a pushing sensation from suction pressure [40]
7.3.7 Thermal Tactile Displays
Thermomechanical actuators provide good performance in terms of displacement, force,
and work per cycle. Thermopneumatic micropumps and microvalves are based on sealed
cavities that have a flexible side [43]. The cavities are filled with a low boiling point
liquid (for instance methyl chloride) and a resistive heater is built inside.
When the heater increases the temperature in the cavity, the pressure grows because of
gas resulting from the liquid-gas phase transition and the flexible side of the cavity is
displaced. Figure 7.13 shows the actuator proposed in [44]. It consists of a small cylinder
made of copper with one end sealed with tin and the other with a flexible diaphragm.
A signal diode has been chosen as the heater due to its small size, although it can be
1.5mm
s
2mm
1
diode
guide
dielectric
cable
Heating
I
Ground
Side view
Figure 7.13
Thermomechanical actuator [44]
