Insertable microelectrode arrays can be used to activate neurons or to sense neural signals for use in prosthetics. The relationship of the microelectrodes to the neurons is determined by random alignment and by biocompatibility. Issues that determine the biocompatibility of insertable microelectrode arrays were investigated. Arrays were implanted into the cortex of rabbit brain and fixed to the skull. Following six-month survival, neuron density as a function of distance from the shafts of the arrays was measured to assess destruction of neurons. Results from a limited number of tests indicated that there was minimal tissue response along the sides of the shafts when shafts were well sharpened, had sufficiently small tip angles, and were clean. Tissue was usually more reactive at the tips of the shafts. It was concluded that silicon microshafts of appropriate shaft and tip design were biocompatible along the sides of the shaft, but that relatively severe reactions could be anticipated at the tips. Recording or stimulation sites should be located away from the tips on the sides of the shafts for better coupling with individual neurons. Measurement of neuron density as a function of distance from the shafts was a sensitive and quantitative technique for assessing biocompatibility. Additional measures such as glial density as a function of distance from the shafts, and incidence of microhematoma formation were proposed.

No abstract

Articles you may be interested inInfluence of boron-interstitials clusters on hole mobility degradation in high dose boron-implanted ultrashallow junctions Impact of the end of range damage from low energy Ge preamorphizing implants on the thermal stability of shallow boron profiles

No abstract

A new dopant selective etching technique, which uses pulsed anodizing voltages applied to silicon samples in KOH : HrO dutioas, has been developed. The use of pulsed anodization causes passivatlon of ptype silicon while n-type silicon continues to etch, making it possible to selectively etchstop on ptype material. These results are consistent with a process which is rate limited by holes in the semiconductor. To demonstrate this technique, a 12-pm-thick ptype membrane was formed. This method differs from the conventional p-n junction etch-stop in that the performance of the etch-stop does not depend on the rectifying characteristics of the diode or on the magnitude of its leakage current. This paper presents data on the passivatlon of ptype and a-type silicon under pulsed anodization conditions for a broad range of KOH concentrations and temperatures. Additionally, the application for etchstopping is presented.