Fabrication of flat electrodes utilizing picosecond laser manufacturing technology: Preliminary study for fabrication of a novel transverse intrafascicular multichannel electrode

Over the last decade we developed methods for the fabrication of laser-structured electrode arrays for neural engineering. For these electrode arrays a metal foil was structured with a 1064 nm Nd:YAG laser in the nanosecond pulse regime and placed within a silicone rubber substrate. Due to process restrictions the individual electrode sites are not in plane with the upper layer of the silicone rubber. Here, a new laser in the picosecond regime (355 nm Nd:YVO₄) was used for laser-structuring. This allowed the fabrication of a novel electrode array out of a 25 μm thick sheet of MP35N metal with thinned-down and buried tracks as well as fixations for the electrode sites and contact pads. For the opening of the single electrodes two different processes, hatching and cutting, have been tested. Due to the interaction of the laser with the metal hatched electrodes had an increased surface area which was investigated with electrochemical measurements. The individual thicknesses of the layers were measured with a novel way of directly laser cutting the electrodes and measuring under a light microscope.

I. Introduction

Electrode arrays for neuroprosthetics come in different configurations and fabrication technologies depending on the intended interface region in the nervous system. A main classification can be done in flexible and non-flexible electrode arrays as well as superficial or penetrating [1]. This paper deals with flexible electrode arrays. Commonly these are fabricated in a cleanroom process with polyimides or Parylene C as a base or by laser structuring with a foundation of silicone rubber (poly(dimethylsiloxane), PDMS) [2] [3].