The Piezoresistivity, Boundary Currents Interface
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, Shell 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, Shell interface are added to the Model Builder.
In addition, the Multiphysics Couplings node is added, which automatically includes the multiphysics coupling feature Piezoresistive Effect, Boundary Currents.
The participating Electric Currents, Shell interface by default adds the Piezoresistive Material 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 Piezoresistive Effect, Boundary Currents multiphysics coupling node can be active only on the selection where both features Piezoresistive Material and Linear Elastic Material (or Hyperelastic Material) are active.
In previous versions of COMSOL Multiphysics (up to version 5.2), a specific physics interface called Piezoresistivity, Boundary Currents was added to the Model Builder. Now, a predefined multiphysics coupling approach is used, improving the flexibility and design options for your modeling. For specific details, see The Multiphysics Branch and Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.
Settings for Physics Interfaces and Coupling Features
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.
However, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.
For example, if both Solid Mechanics and Electric Currents, Shell interfaces are added, COMSOL Multiphysics adds an empty Multiphysics Couplings node. You can choose the available coupling feature Piezoresistive Effect, Boundary Currents but the modified settings are not included. In this example the Piezoresistive Material node needs to be added manually.
Coupling features are available from the context menu (right-click the Multiphysics Couplings node) or from the Physics toolbar, Multiphysics menu.
Physics Interfaces and Coupling Features
Use the online help in COMSOL Multiphysics to locate and search all the documentation. All these links also work directly in COMSOL Multiphysics when using the Help system.
Coordinate Systems
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, Shell>Piezoresistive Material>Coordinate System Selection section.
Coupling Feature
The following multiphysics coupling feature node is described in this section:
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Piezoresistive Effect, Boundary Currents
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Theory for the Piezoresistivity Interfaces
Piezoresistive Pressure Sensor Application Library path: MEMS_Module/Sensors/piezoresistive_pressure_sensor