In Vivo Measurements With Robust Silicon-Based Multielectrode Arrays With Extreme Shaft Lengths (original) (raw)
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IEEE Transactions on Biomedical Engineering - IEEE TRANS BIOMED ENG, 2012
We developed and validated silicon-based neural probes for neural stimulating and recording in long-term implantation in the brain. The probes combine the deep reactive ion etching process and mechanical shaping of their tip region, yielding a mechanically sturdy shank with a sharpened tip to reduce insertion force into the brain and spinal cord, particularly, with multiple shanks in the same array. The arrays' insertion forces have been quantified in vitro. Five consecutive chronically-implanted devices were fully functional from 3 to 18 months. The microelectrode sites were electroplated with iridium oxide, and the charge injection capacity measurements were performed both in vitro and after implantation in the adult feline brain. The functionality of the chronic array was validated by stimulating in the cochlear nucleus and recording the evoked neuronal activity in the central nucleus of the inferior colliculus. The arrays' recording quality has also been quantified in vivo with neuronal spike activity recorded up to 566 days after implantation. Histopathology evaluation of neurons and astrocytes using immunohistochemical stains indicated minimal alterations of tissue architecture after chronic implantation.
IEEE Transactions on Biomedical Engineering, 2006
The mechanical behavior of an electrode during implantation into neural tissue can have a profound effect on the neural connections and signaling that takes place within the tissue. The objective of the present work was to investigate the in vivo implant mechanics of flexible, silicon-based ACREO microelectrode arrays recently developed by the VSAMUEL consortium (European Union, grant #IST-1999-10073). We have previously reported on both the electrical [1]-[3] and mechanical [4], [5]
Development of Multisite Microelectrodes for Neuroscience
2002
Neural probes with a 32-site electrode array have been fabricated using an all-dry Si-etch based micromachining process. The fork-like probe shafts were formed by double-sided deep reactive ion etching (DRIE) of a silicon-on-insulator (SOI) substrate, with the buried SiO 2 layer acting as an etch stop. The probe shafts typically had the dimensions of 4-15 mm (length), 25 µm (width), 20-30 µm (height) and a tip taper angle of 4°. An array of electrodes, each 100 µm 2 , as well as Au conductor traces were formed by e-beam evaporation. Both Ir and Pt were used as electrode material and focused ion beam (FIB) studies, as well as electrical measurements, showed differences between these materials. Also a post process cleaning procedure was developed to remove process residues from the electrode surface. SEM studies showed well defined straight probe shafts with sharp probe tips. The function was verified in bench-top measurements and probes have been successfully used by neuroscientists in brain preparations. The next generation of probes, with 64-sites, have already been designed and are under way in the manufacturing process.
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2003
This study investigated the use of planar, silicon-substrate microelectrodes for chronic unit recording in the cerebral cortex. The 16-channel microelectrodes consisted of four penetrating shanks with four recording sites on each shank. The chronic electrode assembly included an integrated silicon ribbon cable and percutaneous connector. In a consecutive series of six rats, 5/6 (83%) of the implanted microelectrodes recorded neuronal spike activity for more than six weeks, with four of the implants (66%) remaining functional for more than 28 weeks. In each animal, more than 80% of the electrode sites recorded spike activity over sequential recording sessions during the postoperative time period. These results provide a performance baseline to support further electrode system development for intracortical neural implant systems for medical applications.
Experimental neurology, 2005
Implantable silicon microelectrode array technology is a useful technique for obtaining high-density, high-spatial resolution sampling of neuronal activity within the brain and holds promise for a wide range of neuroprosthetic applications. One of the limitations of the current technology is inconsistent performance in long-term applications. Although the brain tissue response is believed to be a major cause of performance degradation, the precise mechanisms that lead to failure of recordings are unknown. We observed persistent ED1 immunoreactivity around implanted silicon microelectrode arrays implanted in adult rat cortex that was accompanied by a significant reduction in nerve fiber density and nerve cell bodies in the tissue immediately surrounding the implanted silicon microelectrode arrays. Persistent ED1 up-regulation and neuronal loss was not observed in microelectrode stab controls indicating that the phenotype did not result from the initial mechanical trauma of electrode implantation, but was associated with the foreign body response. In addition, we found that explanted electrodes were covered with ED1/MAC-1 immunoreactive cells and that the cells released MCP-1 and TNF-a under serum-free conditions in vitro. Our findings suggest a potential new mechanism for chronic recording failure that involves neuronal cell loss, which we speculate is caused by chronic inflammation at the microelectrode brain tissue interface. D
Chronic Neural Recording Using Silicon-Substrate Microelectrode Arrays Implanted in Cerebral Cortex
IEEE Transactions on Biomedical Engineering, 2004
An important aspect of the development of cortical prostheses is the enhancement of suitable implantable microelectrode arrays for chronic neural recording. The objective of this study was to investigate the recording performance of silicon-substrate micromachined probes in terms of reliability and signal quality. These probes were found to consistently and reliably provide high-quality spike recordings over extended periods of time lasting up to 127 days. In a consecutive series of ten rodents involving 14 implanted probes, 13/14 (93%) of the devices remained functional throughout the assessment period. More than 90% of the probe sites consistently recorded spike activity with signal-to-noise ratios sufficient for amplitudes and waveform-based discrimination. Histological analysis of the tissue surrounding the probes generally indicated the development of a stable interface sufficient for sustained electrical contact. The results of this study demonstrate that these planar silicon probes are suitable for long-term recording in the cerebral cortex and provide an effective platform technology foundation for microscale intracortical neural interfaces for use in humans.
Silicon sieve electrodes for neural implants-in vitro characterisation and in vivo recordings
Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol.20 Biomedical Engineering Towards the Year 2000 and Beyond (Cat. No.98CH36286), 1998
An in vitro model was developed to characterise the electrical properties of silicon microfabricated recording electrodes, using a Cu-wire mimicing a neural signal source. Phosphorous doped electrodes were used to achieve an all silicon device. The model was used to study signal amplitude as a function of distance between the electrode surface and the signal source. Signal crosstalk to neighbouring electrodes on the chips were recorded.The crosstalk was found to be 6 dB using an external reference electrode. Improvements were accomplished with an on chip reference electrode giving an amplitude crosstalk suppression of 20 dB. It was found that the amplitude decreased by a factor of 2 at a distance of 50 pm between the electrode surface and the signal source. Sieve electrodes were also implanted in the rat sciatic nerve and following a 10 week nerve regeneration period the dorsal and ventral (L5) roots in the spinal cord were stimulated. Compound action potentials were recorded via the chip. Lower leg muscle contraction activity was also induced by stimulating the regenerated sciatic nerve via the sieve electrode.
Factors influencing the biocompatibility of insertable silicon microshafts in cerebral cortex
IEEE Transactions on Biomedical Engineering, 1992
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.
Deep-brain silicon multielectrodes with surface-modified Pt recording sites
2012 IEEE Sensors, 2012
Extreme-long (up to 70 mm) Si neural multielectrodes are presented for the first time. Probes with different shaft lengths (15-70 mm) were formed by deep reactive ion etching and have been equipped with Pt recording sites of various configurations. In vivo measurements on rodents indicated good mechanical stability, robust implantation and targeting capability, and high quality signals from different locations of the cerebrum have been recorded. The accompanied tissue damage was characterized by histology. With platinum electroplating, electrical impedance reduction was achieved, the improved charge transfer capability was characterized by cyclic voltammetry.