Methodologies for damage identification in MEMS structures

While significant research is focused on the design and fabrication of the MEMS devices, studies on in-service failure evolution and the consequences of failure/damage are limited. Long term embedding and reliable performance of MEMS devices in systems require understanding of failure evolution and recalibration/retuning of the devices. The objective of this research is to study the effects of micro-mechanical damage on MEMS device response and develop techniques for monitoring device failure. This work entails the development and validation of models for simulating device performance and emulating the response of damaged devices. A device level to system level hierarchical methodology is developed to simulate the electro-mechanical operation of MEMS devices. The methodology is illustrated using MEMS-based accelerometer as an example. The response of undamaged devices and devices with a damaged mechanical stage can be simulated using this method. The emulation of a damaged device is carried out using a special finite element developed to represent cracks in the mechanical stage of the MEMS device. An inverse damage detection methodology is formulated using the emulated device response, a local optimization technique and the response from a physical device which enables detection and localization of damage. The damage detection method can establish, while in operation, the extent and the location of damage in the MEMS device. Experimentation with a commercial MEMS accelerometer is performed to measure the characteristics of a physical device and the effectiveness of the damage detection method. Some correlations with experiments are presented. The impact of this research is on improved device reliability and robustness as well as self-calibration features of MEMS devices.