MetalMUMPs-Based Piezoresistive Strain Sensors for Integrated On-Chip Sensor Fusion

In this paper, polysilicon-based microelectro-mechanical system (MEMS) piezoresistive strain sensors manufactured with acoustic emission sensors and accelerometers on the same device are introduced. Three strain sensors are placed in horizontal, vertical, and angled directions to extract the principle strains, and manufactured using MetalMUMPs. The influences of sensor position on the silicon substrate and trenching to the strain transfer from structure under loading to polysilicon layer are numerically demonstrated and experimentally validated. The characterization experiments include monotonic, cyclic, and fatigue mechanical loading and thermal loading. The performance of MEMS strain sensors is compared with conventional metal gauges. While the strain transfer from structure to polysilicon is limited due to the stiffness of package, and the location of strain sensors on the substrate, the gauge factor of MEMS strain sensors is about twice of metal gauges. Combining strain sensors on the same package of other structural health monitoring (SHM) sensors can tackle several limitations of SHM methods, such as the need of redundant measurement to increase the reliability and define idle/active mode of acoustic emission sensor using strain sensor to reduce the power consumption, and enable integrating energy harvesting devices.