Nowadays, MEMS (Micro-Electro-Mechanical Systems) accelerometers play a crucial role in various applications such as inertial navigation, earthquake detection, spacecraft guidance, geophysical sensing, and structural monitoring.

These microfabricated structures offer advantages such as small size, lightweight, low cost, low power, and easy integration with semiconductor technology, making them widely adopted in different fields.

Researchers at INL have recently published a study introducing a micromachining technique to create complex MEMS structures for multi-axis sensing. The developed sensor uses a capacitive open-loop operation and features a hierarchical design resembling matryoshka dolls. This design allows for simple fabrication and operation, making it suitable for structural monitoring systems.

The sensor comprises a double proof-mass hierarchical design with separate electrode sets for in-plane differential measurements. It operates based on changes in capacitance resulting from accelerations in different directions – accelerations in the xx and yy directions affect the gap of the differential sensing electrodes, leading to a differential capacitance change, while zz acceleration affects non-differentially their overlapping area. To detect zz acceleration direction, out-of-plane parallel plates are added to the device using suspended metallic membranes.

Inês Garcia, one of the authors of this study and a member of the IMiNa research group, explains that “the proposed design does not require any complicated integration or post-assembly process, allowing for the fabrication of a small footprint 3-axis MEMS accelerometer”.

The study, under the project (Link4S)ustainability , successfully validated that the proposed fabrication process can produce functional multi-structure silicon-on-insulator (SOI)-based devices with integrated suspended metallic membranes.