Project P9: Resonant magnetoelectric sensor systems for the measurement of deep brain stimulation

该项目的目标是谐振磁电传感器的制造和研究，以及三维传感器和包含模拟信号调理电路的传感器阵列的实现。传感器的性能将通过使用真实的人类头部模型进行实验，并通过测量来自深部脑刺激器患者的生物磁信号来验证。重点是高频（100hz以上），窄带宽（小于2hz）的周期性信号，例如来自深部脑刺激或特定的感觉诱发电位。为了测量这些高频信号或其谐振表面的谐波，将开发采用真空封装的微机械ME传感器，以达到较高的机械质量因子。传感器的谐振频率通过设计或在操作中通过集成调谐机构调整到特定的信号频率。这些MEMS ME传感器将与低噪声放大器和模数转换器混合集成到传感器系统中。使用精密装配技术，3d传感器模块和传感器阵列将被构建。为了制造这些多传感器模块，研究了交换偏置层堆叠作为磁致伸缩元件，不需要外部偏置场。为了测量ME传感器模块的灵敏度、分辨率和指向性，开发并应用了一种专用的测量装置，该装置由三个正交的磁场线圈和具有不同电导率区域的逼真头模组成。随后，本项目的MEMS传感器将与P4、P5和P6项目中合适的传感器一起在相关的神经医学应用中进行评估。首先，我们测量放置在头部幻像中的大脑起搏器的高频谐波。然后对患者脑起搏器产生的伪信号进行测量，并对信号重建算法的质量进行评价。通过脑电和脑磁图的同步配准，比较了头皮上的信号质量和有效性，量化了它们之间的相互影响。进一步，研究了32个触点的商业刺激电极在不同布线配置下的场分布差异。

The project targets on the fabrication and investigation of resonant magnetoelectric (ME) sensors and the realization of 3D-sensors and sensor arrays including analog signal conditioning circuits. The sensor performance will be validated by experiments using a realistic phantom of the human head and by the measurement of biomagnetic signals from patients with deep brain stimulators.The focus is on high frequency (above 100 Hz), narrow bandwidth (less than 2 Hz) periodic signals originating for instance from deep brain stimulation or specific sensory evoked potentials. For the measurement of these high frequency signals or their harmonics resonant surface micromachined ME sensors will be developed which reach high mechanical quality factors by vacuum encapsulation. The resonant frequency of the sensors is adjusted by design or in operation by integrated tuning mechanisms to the specific signal frequency. These MEMS ME sensors will be hybrid-integrated with low-noise amplifiers and analog-digital-converters to sensor systems. Using precision assembly technologies 3D-sensor modules and sensor arrays will be built. For the fabrication of these multi-sensor modules exchange-bias layer stacks as magnetostrictive component are investigated which do not have a need on external bias fields. For the measurement of sensitivity, resolution and directivity of the ME sensor modules a dedicated measurement set-up with three orthogonal magnetic field coils and a realistic head phantom with regions of different electrical conductivities is developed and applied. Subsequently, the MEMS sensors from this project along with suitable sensors from projects P4, P5 and P6 will be evaluated in relevant neuro-medical applications. At first, we measure high frequency harmonics of a brain pacemaker positioned in the head phantom. Then the artefact signal originating from a patient`s brain pace maker is measured and the quality of signal reconstruction algorithms is evaluated. By simultaneous registration of EEG and MEG we compare the signal quality and validity on the scalp and quantify their mutual influence. Further on, the differences in the field distribution of commercial stimulation electrodes with 32 contacts for different wiring configurations are investigated.