Micro Electro Mechanical Systems (MEMS) consist of micron scale components which interact with their surrounding environment as sensors, actuators or both. Classic examples of consumer MEMS devices include accelerometers, micromirrors and microphones. The technology continues to advance, with gravity sensing and biomedical devices emerging.

Xi has design experience with both electrostatic and piezoelectric signal transduction, for mass market and bespoke industrial applications. Relative to macro scale systems, the large surface area to volume ratios in MEMS increase the importance of electromagnetic and fluid dynamic effects. A multiphysics approach is therefore fundamental to the design of MEMS devices for which Xi has a proven track record in across physical domains and orders of scale.

The fabrication process for MEMS devices emerged from semiconductor techniques where thin layer deposition, photolithographic patterning and etch steps define the geometry. By selectively patterning and etching sacrificial layers it is possible to release mechanical structures which can form the basis of a transducer. An understanding of how this process flow affects structural topology and device behaviour can be critical to the manufacturability of a device.

MEMS geometries often demand a fully-coupled multiphysics approach, with the sensitivity of mechanical structures to both viscous damping and electrostatic spring softening being two common examples. Device reliability can be a significant concern but stiction, thermal cycling, shock and vibration can all be mitigated through simulation.

COMSOL Multiphysics is our principal modelling platform, which gives us the ability to solve for a range of physical domains including structural mechanics, acoustics, fluid dynamics and electromagnetics. We have extensive experience with all kinds of MEMS concerns: the use of shell or membrane elements to compute thin film mechanics; contact simulations for stress or stiction recovery analysis; fully-coupled electro-mechanics for pull-in and resonance extraction.

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