The optoacoustic stimulation of the peripheral hearing organ activates the central hearing system. For the potential application in hearing aids, we additionally used an absorber on the tympanic membrane that increased the central neuronal activation.
Significance: Optoacoustic stimulation offers an alternative stimulation strategy for the hearing organ. To serve as the base for a novel auditory prosthesis, the optoacoustic stimulation must be biocompatible and energy-saving.
Aim: Enhancing the efficiency of optoacoustic stimulation while reducing the energy input in a suited animal model.
Approach: Optoacoustically induced auditory brainstem responses (oABRs) were recorded after the pulsed laser irradiation of the tympanic membrane (TM) in mice. The results were compared with the ABRs induced through acoustic click stimulation. In addition, self-adhesive absorbing films were applied on the TM before the optoacoustic stimulation to investigate their effect on the resulting ABRs.
Results: Using an absorbing film on the TM during optical stimulation led to considerably enhanced oABR wave I amplitude values compared with the stimulation of the bare TM. When using our stimulation strategy, we induced oABR waves in the 50% to 60% range of the acoustical stimulation reached with 80-dB SPL click stimuli.
Conclusions: The mouse model can be used for certain developmental work for an optoacoustic auditory prosthesis. Using absorbing films on the TM during optical stimulation considerably enhances oABR wave I amplitude. Optimization of the stimulation strategy could further enhance the efficiency within biocompatibility margins.
Microstructural and crystallographic characterizations of electromigration induced voiding and damage in Al and Al-2% Cu interconnects are presented. Scanning electron and focussed ion beam micrographs show that extended voiding in wide lines and transgranular slit voids in near bamboo lines are the preferred failure morphologies. Electron back scattered diffraction analysis of transgranular slit failure sites show a preferred <110> slit void orientation. Estimates of stresses required for stress assisted void growth in unpassivated interconnects are shown to be reasonably close to measured stress levels in films and interconnects. The transgranular void process is shown to be preferred over boundary voiding based on usual estimates for the variation of surface energy and random boundary energies in Al. Finally, line edge void growth into transgranular slit failures at favorably stressed and crystallographically oriented grain sites is presented as an empirical model for the observed electromigration induced failures in near bamboo interconnects lines.
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