A self-assembled 3D microelectrode array

Recording a neural ensemble has been an extremely successful experimental paradigm allowing real-time interpretation of neural codes as well as the detection of dynamic changes within a process. In recent years, microfabricated electrodes have attracted a great deal of attention for recording neural ensembles with superior resolution and spatial density. A 3D microfabricated electrode is particularly attractive since it yields enhanced performance with regard to spike sorting and single unit detection. In this paper, we describe a self-assembly process for fabricating 3D microelectrode arrays in silicon. The electrode array is composed of four silicon shanks (200 mu m wide, 4 mm long and 30 mu m thick) with polyimide-filled V-groove joints at the back end and four 20 x 20 mu m(2) recording sites (200 mu m separation) at the tip. The shanks automatically fold to a vertical configuration upon proper heat treatment, hence creating a 3D configuration without the need for any manual assembly. Impedance and electrical test-signal measurements were used to verify the electrode functionality after the folding process.