a) Use thermal expansion or contraction of materials.
b) Use various materials with different coefficients of thermal expansion.
EXAMPLE:
The fine adjusting of the mechanical stage of a microscope can be performed by utilizing the controlled linear expansion of an electrically heated metal rod.
Bi-metallic plates made up of materials which have different coefficients of thermal expansion, are often used as thermo-mechanical actuators to open or close the windows of a greenhouse, for example.