Gold nanopillar microelectrodes on low temperature curing polyimide for the interface with electrogenic cells

Microelectrodes are a powerful tool for interfacing neural tissue with electronics, both for in vitro and in vivo. So called microelectrode arrays allow for electrical recordings as well as for electrical stimulations at many parallel sites. Their design and substrate may vary strongly with the field of application. For in vivo implants often flexible substrates are favoured causing low mechanical stress in the tissue. For the first time this type of flexible microelectrode array (MEA) chip shall be combined with the relatively new approach of nanostructured electrodes. Nanostructures help here to increase the electrode´s surface and decrease its impedance resulting in a good the signal to noise ratio. This paper describes the fabrication process of Gold nanopillar microelectrode arrays (MEA) on low temperature curing polyimide for the interface with electrogenic cells. The low temperature curing polyimide is characterized and discussed in terms of electrical and mechanical properties. It is shown that using the proposed methods vertically aligned gold nanopillars can easily be integrated into a micro system on a flexible substrate. We found that electrical and mechanical properties of the polyimide layer strongly depend on its thickness.