A silicon neural probe fabricated using DRIE on bonded thin silicon

A silicon neural probe fabricated using a deep reactive ion etching based process on 250 μm thin silicon wafers was developed. The fabricated probes replicate the design of soft parylene-C based probes embedded in dissolvable needles and can therefore also be used to test the encapsulation properties of parylene-C in-vivo without introducing additional effects introduced by the dissolvable gel. The process also demonstrates the possibility of performing conventional photolithography on substrates bonded to a handle wafer using a backgrinding liquid wax (BGL7080) as an adhesive. This technique would allow integration of Si wafer thinning into the fabrication of neural probes, potentially allowing a range of neural probes of different thicknesses to be fabricated. Fabricated probes were characterized using electrochemical impedance spectroscopy (EIS) yielding a measured impedance value of ~80 kΩ at 1 kHz for 15 μm by 115 μm platinum electrodes, indicating that extracellular neural recordings are possible. The neural probes were inserted into the substantia nigra of a mouse that showed successful recording of neural activity. Probes fabricated using this technique can thus be potentially used in the study of Parkinson's disease.