Piezoresitance
The piezoresistive effect describes the changing electrical resistance of a material due to applied mechanical stress. The piezoresistive effect differs from the piezoelectric effect. In contrast to the piezoelectric effect, the piezoresistive effect only causes a change in resistance, it does not produce electrical charges.
Piezoresistive effect in semiconductors
The piezoresistive effect of semiconductor materials can be several magnitudes larger than the geometrical piezoresistive effect in metals and is present in materials like germanium, polycrystalline silicon, amorphous silicon, and single crystal silicon.