When an electric current flows through a solid or liquid with finite conductivity, electric energy is converted to heat through resistive losses in the material. The heat is generated on the microscale when the conduction electrons transfer energy to the conductors atoms through collisions.

Joule heating is in some cases unwanted, and efforts are made to reduce it. However, many applications rely on Joule heating; some of these use the effect directly, such as cooking plates, while other applications, such as microvalves for fluid control, use the effect indirectly through thermal expansion.

Deformation of a Thermomechanical Microvalve

In this example, a parametric study shows how an increasing voltage applied to each of the legs of a microvalve leads to increased temperature, imposing deformation.