A multi-axis piezoresistive MEMS sensor for acoustic emission
In this study, we present an approach for three-dimensional acoustic emission (AE) sensing based on the structure of a liquid-on-piezoresistive beam. The sensor has three piezoresistive beams, covered with silicone droplets, facing three orthogonal directions in order to produce directivity, and to measure three-dimensional AE. Since droplet surface tension is dominant over gravity at microscale, the liquid can keep its shape in any position. Different with conventional AE sensor, the proposed three-dimensional sensor can be downscaled since the beams were piezoresistor-based. Indeed, the assembled chips have the dimensions of 2.8mm×2.8mm×2.8mm. Experiment results demonstrate that the device has different frequency characteristics depending on vibrating direction, thus it can measure both in-plane and out-of-plane AE waves. Furthermore, the device has a clear bi-directional pattern, which is useful for AE source localization.