A smart acoustic emission and mechanical impedance hybrid sensor with static force detecting and dynamic measuring capabilities

This paper presents a state-of-the-art intelligent acoustic emission (AE) and mechanical impedance hybrid sensor (Fig. 1). The sensor can be operated in two modes: 1) sensing acoustic waves emitted from an external source with the function of being able to detect the static force at installation; 2) measuring the mechanical impedance of the interested object/material by exerting a dynamic force on the object and sensing its feedback velocity. This unique sensor is composed of three major core elements: a micromachined wavy-shaped sensing element made with multi-layer piezoelectric polymer (PVDF) films; a micromachined strain gage made on a patterned SU-8 flexible substrate for force/velocity detection; a diced PZT plate for AE sensing and AE coupling to PVDF element. The device working principle, fabrication and testing are described in the text. Experimental results of pencil lead fracture and material characterization demonstrate the functionality of the developed sensor.