The Piezoresistivity, Boundary Currents predefined multiphysics coupling interface (), found under the Structural Mechanics>Piezoresistivity branch () when adding a physics interface, combines the Solid Mechanics and Electric Currents in Shells interfaces to simulate the piezoresistive effect. This multiphysics interface is appropriate for situations in which the thickness of the piezoresistive layer is much less than that of the structural layer.

When this multiphysics interface is added using the Model Wizard, a Solid Mechanics interface and an Electric Currents in Shells interface are added to the Model Builder.

In addition, the Multiphysics Couplings node is added, which automatically includes the multiphysics coupling feature Piezoresistivity, Boundary Currents.

The participating Electric Currents in Shells interface by default adds the Piezoresistive Shell node with its selection set to all domains. This node can also be added manually to the interface similar to any other material model therein. All piezoresistivity properties are entered in this node.

The Piezoresistivity, Boundary Currents multiphysics coupling node can be active only on the selection where both features Piezoresistive Shell and Linear Elastic Material (or Hyperelastic Material) are active.

When physics interfaces are added using the predefined couplings, for example Piezoresistivity, Boundary Currents, specific settings are included with the physics interfaces and the coupling features.

For example, if both Solid Mechanics and Electric Currents in Shells interfaces are added, COMSOL Multiphysics adds an empty Multiphysics Couplings node. You can choose the available coupling feature Piezoresistivity, Boundary Currents but the modified settings are not included. In this example the Piezoresistive Shell node needs to be added manually.

When setting up a model, the coordinate systems used for the participating physics interfaces should be consistent. In particular, the selected item for the Coordinate system menu under the Solid Mechanics>Linear Elastic Material>Coordinate System Selection section should match the one for the Coordinate system menu under the Electric Currents in Shells>Piezoresistive Shell>Coordinate System Selection section.