The Piezoresistivity, Shell predefined multiphysics coupling interface (), found under the Structural Mechanics>Piezoresistivity branch () when adding a physics interface, is used when the structural layer is thin enough to be treated by the Shell interface, but the conducting and piezoresistive layers are still much thinner than the structural layers.

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

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

The participating Electric Currents in Shells interface by default adds the Piezoresistive Shell node with its selection set to all domains. (Such a node can also be added manually to the corresponding interface.) All piezoresistivity properties are entered in this node.

The Piezoresistivity, Shell multiphysics coupling node can be active only on the selection where both a Piezoresistive Shell and a Linear Elastic Material feature are active.

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

For example, if both Shell and Electric Currents in Shells interfaces are added, COMSOL adds an empty Multiphysics Couplings node. You can choose the available coupling feature Piezoresistivity, Shell 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 Shell>Linear Elastic Material>Shell Local System>Coordinate System Selection section should match the one for the Coordinate system menu under the Electric Currents, Shell>Piezoresistive Shell>Coordinate System Selection section.