Fatigue testing of integrated thin film metal membranes for implantable biomedical pressure sensors

Abstract

The longevity of thin film membranes is vital for the lifetime monitoring of fluid pressure inside the human body. However, aging and mechanical fatigue of the thin film material hinders the long-term reliability of implantable pressure sensors. Despite this, designers tend to neglect the fatigue life analysis of thin films in the design and fabrication of MEMS pressure sensors. Here, we present a low-cost fatigue testing system, which is custom designed from a modern multimedia speaker and subwoofer system. The subwoofer acts as an acoustic booster to amplify the sound vibrations into large stress amplitudes required for displacing the thin film membranes. A Keyence laser displacement sensor records the displacements of the thin films triggered in response to the sound-based stress amplitudes. A scanning electron microscope (SEM) is used in observing the surfaces of the thin films. An FEA parametric study and the fatigue testing results show significant correlations, except for the displacements values as the input Gaussian random vibrations are exaggerated in the experiments to visualize the bursting nature of the thin film membranes.