MEMS Module

Multiphysics Coupling for Hygroscopic Swelling

When Solid Mechanics is combined with one of the Transport of Diluted Species or Transport of Diluted Species in Porous Media interfaces, a new multiphysics coupling called Hygroscopic Swelling is created. It has the same settings as the Hygroscopic Swelling subnode to the material model nodes. With this new multiphysics coupling, you are able to transfer a concentration of moisture, computed in the Transport of Diluted Species or Transport of Diluted Species in Porous Media interfaces, into a hygroscopic swelling strain.

Moisture concentration and deformations in a MEMS pressure sensor due to hygroscopic swelling. (The particular example shown here uses the shell interface in addition to the hygroscopic swelling feature. The shell interface is available with the Structural Mechanics Module.) Moisture concentration and deformations in a MEMS pressure sensor due to hygroscopic swelling. (The particular example shown here uses the shell interface in addition to the hygroscopic swelling feature. The shell interface is available with the Structural Mechanics Module.)

Moisture concentration and deformations in a MEMS pressure sensor due to hygroscopic swelling. (The particular example shown here uses the shell interface in addition to the hygroscopic swelling feature. The shell interface is available with the Structural Mechanics Module.)

Perforations Feature for Thin-Film Flow

A new perforations feature is available for thin-film damping, enabling the modeling of thin-film flow in structures with etch holes.

The perforations feature acts as a sink for gas that is proportional to both the ambient pressure and to the pressure difference with respect to the ambient pressure on the other side of the perforated surface. The constant of proportionality is known as the Perforation admittance (Y) and can either be defined directly or determined from the model as per Bao (M. Bao and H. Yang “Squeeze film air damping in MEMS”, Sensors and Actuators A: Physical, vol. 136, no. 1, 3–27, 2014).

The Perforations settings window with the Bao model being used for the Perforation admittance. The Perforations settings window with the Bao model being used for the Perforation admittance.

The Perforations settings window with the Bao model being used for the Perforation admittance.

Out-of-Plane Motion Option for Border Flow Boundary Condition

A new option is available for the Border Flow boundary condition for thin-film flow. Selecting Out-of-plane motion for the Border flow type calculates the pressure gradient at the boundary using the model of Gallis and Torczynski (M. A. Gallis and J. R. Torczynski, “An Improved Reynolds-Equation Model for Gas Damping of Microbeam Motion”, Journal of Microelectromechanical Systems, vol. 13, pp. 653 - 659, 2004). This model has been shown to agree well with detailed CFD and Monte Carlo simulations that model both the thin-film flow domain and the surrounding gas. The model applies for both rarefied and non-rarefied flows up to Knudsen numbers of approximately one.

Point Matrix Evaluation Feature Enables the Display of Tensor Quantities at a Point

The new Point Matrix Evaluation feature (available in the base package) enables the convenient display of tensor quantities at a point. This is particularly useful for the Piezoelectric Devices interface, which defines tensor material properties in both the local and the global coordinate systems. Consequently, it is now possible to view, for example, the elasticity matrix in the global as well as the local system.

New Tutorial: Micropump Mechanism

Micropumps are key components of microfluidic systems, with applications ranging from biological fluid handling to microelectronic cooling. This tutorial simulates the mechanism of a valveless micropump that is designed to be effective at low Reynolds numbers, thus overcoming hydrodynamic reversibility. Valveless pumps are often preferred in microfludic systems because they minimize the risk of clogging and are gentle on biological material. The Fluid-Structure Interaction interface is used to solve for the flow of the fluid and the associated deformation of the structure. Additionally, the Global ODEs and DAEs interface is used to demonstrate how to perform a time-resolved integration of the total flow throughout the pumping cycle.

Fluid flow and von Mises stress within a passive microfluidic flow rectification system. A pumping mechanism is drawing fluid up into the vertical shaft from the horizontal channel. The channel contains two tilted flaps, which respond to the fluid flow by bending. In this case, when fluid is drawn into the vertical channel, asymmetric bending of the flaps results in a much larger flow from the left-hand channel than from the right channel. Fluid flow and von Mises stress within a passive microfluidic flow rectification system. A pumping mechanism is drawing fluid up into the vertical shaft from the horizontal channel. The channel contains two tilted flaps, which respond to the fluid flow by bending. In this case, when fluid is drawn into the vertical channel, asymmetric bending of the flaps results in a much larger flow from the left-hand channel than from the right channel.

Fluid flow and von Mises stress within a passive microfluidic flow rectification system. A pumping mechanism is drawing fluid up into the vertical shaft from the horizontal channel. The channel contains two tilted flaps, which respond to the fluid flow by bending. In this case, when fluid is drawn into the vertical channel, asymmetric bending of the flaps results in a much larger flow from the left-hand channel than from the right channel.

New Tutorial: Piezoelectric Rate Gyroscope

A tuning-fork-based piezoelectric rate gyroscope is analyzed in this tutorial example, which uses the Piezoelectric Devices interface. The direct piezoelectric effect is used to drive an in-plane tuning fork mode, which is coupled to an out-of-plane mode by the Coriolis force, and the resulting out-of-plane motion is sensed by the reverse piezoelectric effect. The geometry of the tuning forks is designed to make sure that the eigenfrequencies of the nearby modes are separated in frequency space. The frequency response of the system is computed and the rotation rate sensitivity is evaluated.

Drive mode (left) and sense mode (right) for a piezoelectric rate gyroscope. The two modes are coupled together by the Coriolis force. Drive mode (left) and sense mode (right) for a piezoelectric rate gyroscope. The two modes are coupled together by the Coriolis force.

Drive mode (left) and sense mode (right) for a piezoelectric rate gyroscope. The two modes are coupled together by the Coriolis force.

New Tutorial: Piezoelectric Energy Harvester

This tutorial shows how to analyze a simple cantilever-based piezoelectric energy harvester using the Piezoelectric Devices interface. A sinusoidal acceleration is applied to the energy harvester and the output power is evaluated as a function of frequency, load impedance, and acceleration magnitude.

Input mechanical power, output electrical power and voltage as a function of load impedance. Input mechanical power, output electrical power and voltage as a function of load impedance.

Input mechanical power, output electrical power and voltage as a function of load impedance.

New Tutorial: Piezoelectric Valve

Piezoelectric valves are frequently employed in medical and laboratory applications due to their fast response times and quiet operation. Their energy-efficient operation dissipates little heat, which is often important for these applications.

In this tutorial, a piezoelectric valve is actuated by a stacked piezoelectric actuator. To model this, the Piezoelectric Devices interface is used in conjunction with the Contact feature. A hyperelastic seal is compressed against a valve opening by the actuator, and the contact pressure is computed.

The von Mises stress on the surface of a piezoelectric valve. The von Mises stress on the surface of a piezoelectric valve.

The von Mises stress on the surface of a piezoelectric valve.

New Tutorial: Disc Resonator Anchor Losses

This tutorial shows how to compute the anchor loss limited quality factor of a diamond disc resonator, using the Solid Mechanics interface. The resonator is anchored to a substrate by a polysilicon post and power is transmitted to the substrate through the post. A perfectly matched layer is used to represent the essentially infinite substrate. The tutorial is based on a paper presented at the COMSOL Conference 2007 in Grenoble (P. Steeneken "Parameter Extraction and Support-Loss in MEMS Resonators", COMSOL Users Conference 2007, Grenoble).

Total displacement of the structure shown with a color scale such that the anchor losses are clearly visible. Total displacement of the structure shown with a color scale such that the anchor losses are clearly visible.

Total displacement of the structure shown with a color scale such that the anchor losses are clearly visible.