Mechanical characterization of neural electrodes based on PDMS-parylene C-PDMS sandwiched system

Manufacturing of neural electrodes based on metal foil and silicone rubber using a laser is a simple and promising method. A handicap of such electrode arrays is the mechanical robustness of the thin metal tracks that connect the electrode sites with the interconnection pads. Embedding of structured parylene C foil in silicone rubber turned out to be an interesting method to increase the robustness. Test samples with 12.5 μm thick platinum tracks and a 15 μm thick embedded and RIE-structured parylene C foil showed more than 800 % higher ultimate strength until breakage of the tracks. Different structured parylene C foil showed increasing robustness with increasing hole-spacing.

I. Introduction

Neural interfaces, more precisely electrocorticography (ECoG) electrodes, have a wide range of medical applications. They can be used for presurgical epilepsy monitoring, as aid for tumor resections or for providing brain-computer interfaces [1]. A manufacturing technology for electrodes with a high spatial resolution based on laser structuring was first described by Schuettler et al. in 2005, using exclusively medical grade silicone rubber (PDMS) as insulation material and metal foil as electrode material [2]. To get a high spatial resolution the laser method allows us manufacturing electrode tracks of platinum foil with a pitch down to [3].