Design and Implementation of a Test System for Brain Electrodes

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Supervisor:
Dr. Jobbágy Ákos Andor
Department of Measurement and Information Systems

In this thesis, I represent the design and the testing process of a measurement setup for in vivo mechanical testing of silicon-based neural electrodes (made by MTA MFA MEMS Laboratory). To integrate a load-cell, a stereotaxic frame and a stepper motor together I designed proper mechanical components and the electronic circuit as well as the measurement and control software. The automated measurement process provides objective results with 1mN resolution. Thanks to the motorized drive, the implantation velocity is steady and adjustable (0.15 – 30 mm/min range) as well as the implantation depth.

Using the previously discussed setup I managed to investigate a variety of electrodes with different geometric parameters (width, thickness, tip) using Sprague Dawley rats in vivo. The surgical environment necessary for the latter process was provided by MTA KPI. To make the evaluation process easier and faster I designed a MatLab based graphical user interface.

Penetration force through dura mater and dimpling as parameters were investigated during these tests. Results showed that the implantation parameters achievable with the investigated neural electrodes depend on the speed of the insertion and the geometrical parameters of the electrode.

This measurement setup is able to investigate the mechanical interaction between different electrodes used in neurophysical experiments and the outer surface of the brain, mainly the dura mater. The results of these experiments provide a good basis for further investigation and manufacturing of silicon based neural electrodes. Also, they can be used to develop new designs in microtechnologies for proper mechanical stability and very low cell damage.

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