SIROF-Mikroelektroden für die neuronale Einzelzellstimulation
- SIROF microelectrodes for single neuron stimulation
van Ooyen, André; Mokwa, Wilfried (Thesis advisor)
Aachen : Publikationsserver der RWTH Aachen University (2010, 2011)
Dissertation / PhD Thesis
Aachen, Techn. Hochsch., Diss., 2010
The coupling of technical systems to biological systems gains increasing impact in the field of biological, medical and pharmaceutical research. An important area of this research is neurobiology, dealing with the development and functionality of neuronal systems. Artificial neuronal networks offer a simplified system to investigate basic neuronal mechanisms. For this, single neuronal cells need to be stimulated and pulse responses of the cells need to be recorded. Like in microelectronics miniaturization is demanded for such devices while maintaining or even improving their properties. A promising approach for stimulation is the application of electroactive electrode materials capable of injecting sufficient amounts of charge over the electrode/tissue interface. therefore microelectrodes with a functional coating of sputtered iridium oxide (SIROF) were fabricated and investigated for extracellular single neuron stimulation in electrophysiological in vitro experiments and biohybrid devices for bidirectional coupling of dissociated networks. In this context the influence of a pulsed plasma source on the film properties of reactive sputtered iridium oxide films with varying oxygen flow and the deposition of SIROF onto a nanostructured galvanic gold was evaluated for the first time. Mechanical stable films suited for stimulation applications were deposited and a parameter space for an optimal film morphology could be determined. The deposition of SIROF onto the nanostructured galvanic gold surface was identified as potential candidate to improve the stimulation capability of SIROF microelectrodes. In a first attempt this surface modification was integrated into the microelectrode manufacturing process. The SIROF microelectrodes were characterized regarding their electrochemical properties and charge injection limits. Additional to electrochemical impedance spectroscopy and cyclovoltammetry the pulse-clamp technique was used for the very first time to investigate the charge injection limits and charge lost of SIROF microelectrodes in current pulse operation. For this approach a customized electronic circuit and measurement software was developed, capable of measuring the charge injection properties of microelectrodes way below 300 um in diameter. By using the pulse-clamp technique it was possible to determine the amount of irreversible charge during an neuronal stimulation pulse and use it a a direct measure of irreversible processes to determine the charge injection limits. Finally the application of SIROF microelectrodes in electrophysiological experiments was demonstrated by stimulating single neurons in dissociated networks in vitro. Furthermore SIROF stimulation microelectrodes were integrated with FET devices for recording to establish bidirectional coupling of neuronal cells into a single chip for the first time, pursuing the development of a new system for extracellular stimulatioin and recording of electrogenic cells in vitro.
- Chair of Materials in Electrical Engineering I and Institute of Materials in Electrical Engineering