One thing to realize about MEMS is that it is mostly used for sensors (accelerometers, gyros, pressure, magnetometers) and actuators. There's a whole journal by that name.
Fundamentally, an oscillator/resonator is the sensing of nothing.
You want the frequency of output to be completely independent of acceleration, strain, rotation, pressure, magnetic/electric field, etc). That's really hard to do and involves a combination of building very robust silicon packaging, minimizing (making symmetric) all contacts to the outside to shield it, and compensating for every possible effect you can measure.
A sensor of nothing is an interesting way of looking at it, I like that characterization. Ideally you shouldn’t be able to infer a single thing about the environment from the signal
Yeah, like all sensors, basically anything you make in MEMS is a temperature sensor, a pressure sensor, an acceleration sensor, and a strain gauge all in one. The trick is to make it only sense the thing you want.
Fundamentally, an oscillator/resonator is the sensing of nothing.
You want the frequency of output to be completely independent of acceleration, strain, rotation, pressure, magnetic/electric field, etc). That's really hard to do and involves a combination of building very robust silicon packaging, minimizing (making symmetric) all contacts to the outside to shield it, and compensating for every possible effect you can measure.