The MEMS Module enables the stationary and dynamic performance of devices to be modeled in two and three dimensions, together with circuit-based modeling of active and passive devices. In the frequency domain, powerful tools are available to model devices driven by a combination of AC and DC signals or forces. Predefined physics interfaces, referred to as MEMS physics interfaces, address a wide range of physical phenomena that are employed in MEMS sensors and actuators. MEMS physics interfaces are available for simulating structural mechanics, electrostatics, electric currents, piezoelectricity, piezoresistivity, thin-film fluid flow, heat transfer, and electrical circuits. These physics interfaces can also be coupled arbitrarily to solve multiphysics problems, and a number of predefined couplings are also available as MEMS physics interfaces. These include electromechanics (for combining electrostatic forces with structural mechanics), Joule heating, Joule heating and thermal expansion, and fluid-structure interaction (for combining fluid flow with structural mechanics).
For each of the MEMS physics interfaces, the underlying physical principles are expressed in the form of partial differential equations, together with corresponding initial and boundary conditions. COMSOL’s design emphasizes the physics by providing users with the equations solved by each feature and offering the user full access to the underlying equation system. There is also tremendous flexibility to add user-defined equations and expressions to the system. For example, to model Joule heating in a structure with temperature-dependent elastic properties, simply enter in the elastic constants as a function of temperature — no scripting or coding is required. When COMSOL Multiphysics compiles the equations, the complex couplings generated by these user-defined expressions are automatically included in the equation system. The equations are then solved using the finite element method and a range of industrial strength solvers. Once a solution is obtained, a vast range of postprocessing tools are available to analyze the data, and predefined plots are automatically generated to show the device response. COMSOL Multiphysics offers the flexibility to evaluate and visualize a wide range of physical quantities, including predefined quantities such as the temperature, the electric field, or the stress tensor (available through easy-to-use menus), as well as arbitrary user-defined expressions.