Date of Award

Fall 2007

Document Type


Degree Name

Master of Science in Biomedical Engineering - (M.S.)


Biomedical Engineering

First Advisor

Mesut Sahin

Second Advisor

Tara L. Alvarez

Third Advisor

Bryan J. Pfister


One of the major challenges in neural engineering is the tissue damage that occurs during insertion of microelectrodes into the central nervous system. The damage occurs as a result of the dimpling effect that is due to the insertion force. A method which can reduce the penetration force can also reduce dimpling and the resulting tissue damage.

There are two objectives in this thesis. One is to measure the penetration force with Michigan electrodes, which are silicon based electrodes. The second is to reduce the penetration force by using mechanical vibrations.

First, the penetration force was measured in the rat brain. To measure the penetration force, the microelectrode was connected to a load transducer. Because dura is a tough membrane to penetrate, it is usually removed during surgery in experimental animals. The dura mater was not removed in these experiments in order to keep the intactness of the cortex. The microelectrode was pulsed at a rate of 5 Hz using a piezoelectric crystal and a pulse generator.

The results show that the vibration technique is successful in reducing the penetration force by 25%. In this study, we have concentrated only on reducing the penetration force in order to reduce dimpling. To our best knowledge no work has been yet reported on the use of vibrations for reducing electrode penetration force. Chronic experiments will have to be conducted to investigate if the vibrations alone cause any tissue damage.