A micromachined silicon sieve electrode for nerve regeneration applications

A micromachined silicon sieve electrode has been developed and fabricated to record and stimulate individual axons of the peripheral nerve system by utilizing the nerve regeneration principle. The electrode structure is composed of a 15- mu m-thick silicon support rim, a 4- mu m-thick diaphragm containing different-size holes to allow nerve regeneration, and an integrated silicon ribbon cable, all fabricated using boron etch-stop. The diaphragm is etched using reactive ion etching to obtain different size holes with diameters as small as 2 mu m and center-center spacings as small as 10 mu m. The holes are surrounded by 100-200- mu m/sup 2/ anodized iridium oxide sites, which can be used for both recording and stimulation. These sites exhibit low impedances of less than 100 k Omega at 1 kHz and charge delivery capacities in the 4-6-mC/cm/sup 2/ range. The fabrication process is single-sided, has high yield, requires only five masks, and is comparable with integrated silicon ribbon cables. The sieve electrodes were implanted between the cut ends of peripheral taste fibers of rats (glossopharyngeal nerve), and axons have successfully regenerated through the holes.<>