Flexible neural microelectrode arrays reinforced with embedded metallic micro-needles

Neural microprobes with 16 stimulation/recording channels are fabricated employing surface micromachining techniques. Each device integrates a flexible polyimide-based interconnection cable, the array of bonding pads, and 4 parallel shanks hosting the electrode sites, all constructed in a single 3 mask fabrication process. In order to provide the shanks with enough mechanical strength for insertion into the tissue, a 15 μm thick gold micro-needle is embedded inside each shank as the reinforcement structure. A polyimide shell encapsulates the micro-needles from electrode sites and the interconnection lines. The shanks are 4 mm long, 100 μm wide at the base, and 24 μm thick. The electrode sites measuring 20 μm × 20 μm are addressed through gold interconnection lines to reduce the electrodes impedances and consequently improve the signal to noise ratio of the recording signal. This paper presents the details of microprobe fabrication and the preliminary characterization results.