Development and Characterization of Multisite Three-Dimensional Microprobes for Deep Brain Stimulation and Recording

Novel 3-D multichannel microprobes are presented for deep brain stimulation and recording applications. The microprobes offer independent electrode sites around the shaft of the implant, providing the capability to control the profile of injected charge into the tissue. The devices are composed of planar flexible microprobes folded over cylindrical polyurethane shafts with diameters as small as 750 μm . A dramatic enhancement in the density/number of channels and a precise control over the dimensions of the electrode sites are achieved using this approach. The fabricated devices host 16 stimulating and 16 recording channels. The impedance characteristics and long-term behavior of electrodes were studied in acidic and saline solutions under prolonged pulse stress tests. To enhance the charge delivery capacity or reduce the impedances of the channels, iridium (Ir) was electroplated on gold electrode sites. Both Ir and gold channels demonstrate stable characteristics after pulse stress tests longer than 100 million cycles. The in vitro experiments in the whole hippocampus of a C57BL/6 mouse demonstrate the potential application of fabricated microprobes in simultaneous neural stimulation and recording.