Lloyd D. Clark

Factors influencing the biocompatibility of insertable silicon microshafts in cerebral cortex

Issues that determine the biocompatibility of insertable microelectrode arrays were investigated. 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.<<ETX>>

Cesium hydroxide (CsOH): a useful etchant for micromachining silicon

The CsOH-H/sub 2/O etchant system was studied over a range of concentrations (10%-76% by weight) and temperatures (25-90 degrees C). The etch rates of

A Photon-Camera Star Tracker For Stellar Interferometry

A photon-camera star tracker was developed for use in a ground-based optical stellar interferometer. A major advantage gained by using a photon camera as the light detecting element is that it allows the received image to be cross-correlated with any desired spatial function. A theoretical analysis is presented to show that proper selection of a cross-correlation function can result in improved tracking performance. In addition, the optical, electronic, and software design of the star tracker is discussed.

A probabilistic approach to the design of microelectrode layouts for neural signal transducers

Neural signal transducers consisting of arrays of microelectrodes fabricated on a substrate are considered. The geometries and spacings of the microelectrodes have a major impact on the characteristics of the neural signals that are obtained. The design of microelectrode layouts that maximize the probability of obtaining easily detectable neural spikes is discussed. It is shown that a selectivity-noise tradeoff exists. A computer simulation is used to quantify this tradeoff.<<ETX>>

Silicon neural information transducers: current technology, perspectives, and recent results

Advanced neural information transducers are currently under development. Novel micromachined silicon transducer fabrication techniques have been created to facilitate construction of implantable devices which can achieve a high-quality, long-term, neural-electrical interface. The basic functionality of implanted microtransducers has been demonstrated during long-term implants. Current research is focused on the study of the interface during behavioral testing of implanted animals, methods of optimizing information transduction, adaptive detection and encoding circuitry, understanding the electrical properties of the microenvironment surrounding the contacts, and techniques for fabrication of active devices that can function indefinitely during saline immersion. Applications of existing technology are not technically possible for physiological studies and relatively short-term feasibility testing in humans. New understanding of protection of integrated circuits during long-term saline immersion is essential for implementation of advanced long-term integrated systems.<<ETX>>