Magnetoelectric Sensors for Frequency Conversion

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This project is concerned with the research and development of resonant magneto electric (ME) sensors for applications in the fields of magneto encephalography (MEG) and magneto cardiography (MKG). The utilization of these sensors and a frequency conversion method are considered especially promising for achieving a sufficiently low limit of detection in the measurement of low frequency bio magnetic signals, due to resonance amplification and reduction in current noise. ME sensors are to be developed by micro- and nanosystems technology, based on results obtained by multiscale modelling including the readout electronics for front-ends, for the detection of weak bio-magnetic signals while minimizing the noise level. The project will be conducted in close collabora-tion between modelling (Gerken), fabrication (Quandt) and analog signal processing (Knöchel). The first goal comprises volume micromachining of tuning fork sensors and creation of readout electronics which make use of frequency conversion to enable optimum noise suppression and maximum useful signal extraction. These efforts are combined with a theoretical analysis of the noise properties. The second goal will consist of investigation of effect increasing measures for ME cantilever sensors, specifically of tuning fork type. Special aspects concern modifications in the design of the cantilevers (i.e. by integrating mechanical stress concentrators), the integration of magnetic flux concentrators, an increase of the quality factor in resonance (i.e. by vacuum packaging or by using quartz as substrate material) as well as the application of regenerative systems. As a third goal electrical modulation of the ME sensors will be investigated. Fabrication, modelling and control of quartz instead of silicon cantilevers produced by volume micromachining enable an additional electrical modulation of the ME sensors. The aim is to periodically modulate the substrate and its piezoelectric coefficient by an electrical bias field, whereby the magnetic signal caused by magnetostriction causes mixed signals at the mechanical resonance frequency, which enhance the oscillation. If necessary, this project will use the ME composites investigated by projects P1 and P2. The ME sensors will be available as standalone sensors or for system integration by projects P7 - P10 for achieving their corresponding goals.