A micromachined silicon sieve electrode for nerve regeneration applications

A micromachined silicon sieve electrode has been developed and fabricated to record from and stimulate axons/fibers of the peripheral nervous system by utilizing the nerve regeneration principle. The electrode consists of a 15-μm-thick silicon support rim, a 4-μm-thick diaphragm containing different size holes to allow nerve regeneration, thin-film iridium recording/stimulating sites, and an integrated silicon ribbon cable, all fabricated using boron etch-step and silicon micromachining techniques. The thin diaphragm is patterned using reactive ion etching to obtain different size holes with diameters as small as 1 μm and center-center spacings as small as 10 μm. The holes are surrounded by 100-200 μm ² anodized iridium oxide sites, which can be used for both recording and stimulation. These sites have impedances of less than 100 kΩ @ 1 kHz and charge delivery capacities in the 4-6 mC/cm ² range. The fabrication process is single-sided, has high yield, requires only five masks, and is compatible with integrated multilead silicon ribbon cables. The electrodes were implanted between the cut ends of peripheral taste fibers of rats (glossopharyngeal nerve), and axons functionally regenerated through holes, responding to chemical, mechanical, and thermal stimuli.