A 3D tactile sensing element concept based on tridimensional piezoelectric aluminum nitride (AlN) membranes is presented. Detection modes for normal and shear forces are investigated by FEM simulations. Based on these results a design of a functionalized sensing system is performed. The simulation focuses on the mechanical response of pyramidal structures on force transmission across the whole membrane surface. Therefore, an embedded device configuration is defined. The overall aim of these investigations is to find an optimized sensor electrode configuration and to verify the ability to detect normal and shear forces with one element. Additionally, first high aspect ratio pyramidal AlN membrane structures have been successfully fabricated.

This work aims for utilizing human ocular motion for the self-sufficient power supply of a minimally invasive implantable monitoring system for intraocular pressure (IOP). With a proven piezoelectric functionality (d(33) > 5 pm/V), nanocrystalline thin films of aluminum nitride (AlN) provide a good capability for micromechanical energy harvesting (EH) in medical applications. Many d31-mode microcantilever architectures are poorly suited for human-induced EH: Resonant mass-spring-damper systems are tested under high, narrow-band excitation frequencies. However, human motions, e.g. vibrations of eyeballs are marked by their low frequency, unpredictable, mainly aperiodic and time-varying signature. Different vibration types and directions are 3-dimensionally superimposed. Saccadic eye movements are favorable for inertial microgenerators because of their high dynamic loading w

We present tunable lenses based on aluminum nitride membranes. The achievable tuning range in the refractive power is 0 to 25 dpt with an external pressure load of <= 20 kPa. The lenses are manufactured using MOEMS technology. For 500-nm-thick membranes with a diameter of 3 mm, a spherical deflection profile is found. The system provides good long-term stability showing no creep or hysteresis. A model for the refractive power versus applied pressure is derived and validated experimentally. Based on this model, design guidelines are discussed. One essential parameter is the residual stress of the aluminum nitride layer that can be controlled during deposition

A fast identification method of membrane structure parameters is investigated for an early stage of the manufacturing process. The approach consists of performing optical measurement of the modal responses of the membrane structures. This information is used in an inverse identification algorithm based on a FE model.Device characteristics can be determined by measured modal frequencies which are fed into a model based on the FE simulations. The number of parameters to be identified is thereby generally limited only by the number of measurable modal frequencies. A quantitative evaluation of the identification results permits furthermore the detection of defects like cracks which cannot be classified within a FE model.The approach is validated by first measurements which have shown a good correlation between simulated and measured modal frequencies.