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Thomas WM, Zuniga SA, Sondh I, Leber M, Solzbacher F, Lenarz T, Lim HH, Warren DJ, Rieth L, Adams ME. Development of a feline model for preclinical research of a new translabyrinthine auditory nerve implant. Front Neurosci 2024; 18:1308663. [PMID: 38379760 PMCID: PMC10877721 DOI: 10.3389/fnins.2024.1308663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 01/02/2024] [Indexed: 02/22/2024] Open
Abstract
Cochlear implants are among the most successful neural prosthetic devices to date but exhibit poor frequency selectivity and the inability to consistently activate apical (low frequency) spiral ganglion neurons. These issues can limit hearing performance in many cochlear implant patients, especially for understanding speech in noisy environments and in perceiving or appreciating more complex inputs such as music and multiple talkers. For cochlear implants, electrical current must pass through the bony wall of the cochlea, leading to widespread activation of auditory nerve fibers. Cochlear implants also cannot be implanted in some individuals with an obstruction or severe malformations of the cochlea. Alternatively, intraneural stimulation delivered via an auditory nerve implant could provide direct contact with neural fibers and thus reduce unwanted current spread. More confined current during stimulation can increase selectivity of frequency fiber activation. Furthermore, devices such as the Utah Slanted Electrode Array can provide access to the full cross section of the auditory nerve, including low frequency fibers that are difficult to reach using a cochlear implant. However, further scientific and preclinical research of these Utah Slanted Electrode Array devices is limited by the lack of a chronic large animal model for the auditory nerve implant, especially one that leverages an appropriate surgical approach relevant for human translation. This paper presents a newly developed transbullar translabyrinthine surgical approach for implanting the auditory nerve implant into the cat auditory nerve. In our first of a series of studies, we demonstrate a surgical approach in non-recovery experiments that enables implantation of the auditory nerve implant into the auditory nerve, without damaging the device and enabling effective activation of the auditory nerve fibers, as measured by electrode impedances and electrically evoked auditory brainstem responses. These positive results motivate performing future chronic cat studies to assess the long-term stability and function of these auditory nerve implant devices, as well as development of novel stimulation strategies that can be translated to human patients.
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Affiliation(s)
- W. Mitchel Thomas
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States
| | - Steven A. Zuniga
- Department of Otolaryngology-Head and Neck Surgery, University of Minnesota, Minneapolis, MN, United States
| | - Inderbir Sondh
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States
| | - Moritz Leber
- Blackrock Neurotech, Salt Lake City, UT, United States
| | - Florian Solzbacher
- Blackrock Neurotech, Salt Lake City, UT, United States
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, United States
| | - Thomas Lenarz
- Department of Otorhinolaryngology, Medical University of Hannover, Hannover, Germany
| | - Hubert H. Lim
- Department of Otolaryngology-Head and Neck Surgery, University of Minnesota, Minneapolis, MN, United States
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States
| | - David J. Warren
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, United States
| | - Loren Rieth
- Department Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV, United States
| | - Meredith E. Adams
- Department of Otolaryngology-Head and Neck Surgery, University of Minnesota, Minneapolis, MN, United States
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McNamara M, Ersöz A, Han M. A Diagnostic Circuit for Crosstalk Detection in Microelectrode Arrays. INTERNATIONAL IEEE/EMBS CONFERENCE ON NEURAL ENGINEERING : [PROCEEDINGS]. INTERNATIONAL IEEE EMBS CONFERENCE ON NEURAL ENGINEERING 2021; 2021:544-547. [PMID: 34925703 PMCID: PMC8674810 DOI: 10.1109/ner49283.2021.9441164] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Current leakage between channels in microelectrode arrays is a sign of device failure and can lead to shorting of neural signals. The purpose of this project is to detect crosstalk between 32 channels of electrodes. We designed an embedded crosstalk detection system that can stimulate each electrode individually with a constant-current pulse and record voltage transients of the stimulated and adjacent electrodes to generate a matrix of crosstalk values. Charge injection in a phosphate buffered saline solution was used to check the condition of each electrode. A semi-wet condition was then used to determine the percent crosstalk between the channels. The analysis showed that there was minimal crosstalk between the electrodes, except for a known physical defect on the probe. The measurement technique enabled by the electronics circuit has the potential to be used in functional testing and screening of implantable devices.
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Affiliation(s)
- Morgan McNamara
- Biomedical Engineering Department, University of Connecticut, Storrs, CT 06269 USA
| | - Alpaslan Ersöz
- Biomedical Engineering Department, University of Connecticut, Storrs, CT 06269 USA
| | - Martin Han
- Biomedical Engineering Department, University of Connecticut, Storrs, CT 06269 USA
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Nolta NF, Ghelich P, Ersöz A, Han M. Fabrication and modeling of recessed traces for silicon-based neural microelectrodes. J Neural Eng 2020; 17:056003. [PMID: 32947274 DOI: 10.1088/1741-2552/abb9bd] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Chronically-implanted neural microelectrodes are powerful tools for neuroscience research and emerging clinical applications, but their usefulness is limited by their tendency to fail after months in vivo. One failure mode is the degradation of insulation materials that protect the conductive traces from the saline environment. APPROACH Studies have shown that material degradation is accelerated by mechanical stresses, which tend to concentrate on raised topographies such as conducting traces. Therefore, to avoid raised topographies, we developed a fabrication technique that recesses (buries) the traces in dry-etched, self-aligned trenches. MAIN RESULTS The fabrication technique produced flatness within approximately 15 nm. Finite element modeling showed that the recessed geometry would be expected to reduce intrinsic stress concentrations in the insulation layers. Finally, in vitro electrochemical tests confirmed that recessed traces had robust recording and stimulation capabilities that were comparable to an established non-recessed device design. SIGNIFICANCE Our recessed trace fabrication technique requires no extra masks, is easy to integrate with existing processes, and is likely to improve the long-term performance of implantable neural devices.
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Affiliation(s)
- Nicholas F Nolta
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT, United States of America
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Characterization of Parylene-C degradation mechanisms: In vitro reactive accelerated aging model compared to multiyear in vivo implantation. Biomaterials 2020; 232:119731. [DOI: 10.1016/j.biomaterials.2019.119731] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 12/19/2019] [Accepted: 12/25/2019] [Indexed: 11/23/2022]
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Caldwell R, Mandal H, Sharma R, Solzbacher F, Tathireddy P, Rieth L. Analysis of Al 2O 3-parylene C bilayer coatings and impact of microelectrode topography on long term stability of implantable neural arrays. J Neural Eng 2018; 14:046011. [PMID: 28351998 DOI: 10.1088/1741-2552/aa69d3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Performance of many dielectric coatings for neural electrodes degrades over time, contributing to loss of neural signals and evoked percepts. Studies using planar test substrates have found that a novel bilayer coating of atomic-layer deposited (ALD) Al2O3 and parylene C is a promising candidate for neural electrode applications, exhibiting superior stability to parylene C alone. However, initial results from bilayer encapsulation testing on non-planar devices have been less positive. Our aim was to evaluate ALD Al2O3-parylene C coatings using novel test paradigms, to rigorously evaluate dielectric coatings for neural electrode applications by incorporating neural electrode topography into test structure design. APPROACH Five test devices incorporated three distinct topographical features common to neural electrodes, derived from the utah electrode array (UEA). Devices with bilayer (52 nm Al2O3 + 6 µm parylene C) were evaluated against parylene C controls (N ⩾ 6 per device type). Devices were aged in phosphate buffered saline at 67 °C for up to 311 d, and monitored through: (1) leakage current to evaluate encapsulation lifetimes (>1 nA during 5VDC bias indicated failure), and (2) wideband (1-105 Hz) impedance. MAIN RESULTS Mean-times-to-failure (MTTFs) ranged from 12 to 506 d for bilayer-coated devices, versus 10 to >2310 d for controls. Statistical testing (log-rank test, α = 0.05) of failure rates gave mixed results but favored the control condition. After failure, impedance loss for bilayer devices continued for months and manifested across the entire spectrum, whereas the effect was self-limiting after several days, and restricted to frequencies <100 Hz for controls. These results correlated well with observations of UEAs encapsulated with bilayer and control films. SIGNIFICANCE We observed encapsulation failure modes and behaviors comparable to neural electrode performance which were undetected in studies with planar test devices. We found the impact of parylene C defects to be exacerbated by ALD Al2O3, and conclude that inferior bilayer performance arises from degradation of ALD Al2O3 when directly exposed to saline. This is an important consideration, given that neural electrodes with bilayer coatings are expected to have ALD Al2O3 exposed at dielectric boundaries that delineate electrode sites. Process improvements and use of different inorganic coatings to decrease dissolution in physiological fluids may improve performance. Testing frameworks which take neural electrode complexities into account will be well suited to reliably evaluate such encapsulation schemes.
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Affiliation(s)
- Ryan Caldwell
- Department of Bioengineering, University of Utah, Salt Lake City, UT, United States of America
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Caldwell R, Sharma R, Takmakov P, Street MG, Solzbacher F, Tathireddy P, Rieth L. Neural electrode resilience against dielectric damage may be improved by use of highly doped silicon as a conductive material. J Neurosci Methods 2018; 293:210-225. [DOI: 10.1016/j.jneumeth.2017.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 10/01/2017] [Accepted: 10/02/2017] [Indexed: 11/28/2022]
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Wendelken S, Page DM, Davis T, Wark HAC, Kluger DT, Duncan C, Warren DJ, Hutchinson DT, Clark GA. Restoration of motor control and proprioceptive and cutaneous sensation in humans with prior upper-limb amputation via multiple Utah Slanted Electrode Arrays (USEAs) implanted in residual peripheral arm nerves. J Neuroeng Rehabil 2017; 14:121. [PMID: 29178940 PMCID: PMC5702130 DOI: 10.1186/s12984-017-0320-4] [Citation(s) in RCA: 116] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 10/20/2017] [Indexed: 01/08/2023] Open
Abstract
Background Despite advances in sophisticated robotic hands, intuitive control of and sensory feedback from these prostheses has been limited to only 3-degrees-of-freedom (DOF) with 2 sensory percepts in closed-loop control. A Utah Slanted Electrode Array (USEA) has been used in the past to provide up to 81 sensory percepts for human amputees. Here, we report on the advanced capabilities of multiple USEAs implanted in the residual peripheral arm nerves of human amputees for restoring control of 5 DOF and sensation of up to 131 proprioceptive and cutaneous hand sensory percepts. We also demonstrate that USEA-restored sensory percepts provide a useful source of feedback during closed-loop virtual prosthetic hand control. Methods Two 100-channel USEAs were implanted for 4–5 weeks, one each in the median and ulnar arm nerves of two human subjects with prior long-duration upper-arm amputations. Intended finger and wrist positions were decoded from neuronal firing patterns via a modified Kalman filter, allowing subjects to control many movements of a virtual prosthetic hand. Additionally, USEA microstimulation was used to evoke numerous sensory percepts spanning the phantom hand. Closed-loop control was achieved by stimulating via an electrode of the ulnar-nerve USEA while recording and decoding movement via the median-nerve USEA. Results Subjects controlled up to 12 degrees-of-freedom during informal, ‘freeform’ online movement decode sessions, and experienced up to 131 USEA-evoked proprioceptive and cutaneous sensations spanning the phantom hand. Independent control was achieved for a 5-DOF real-time decode that included flexion/extension of the thumb, index, middle, and ring fingers, and the wrist. Proportional control was achieved for a 4-DOF real-time decode. One subject used a USEA-evoked hand sensation as feedback to complete a 1-DOF closed-loop virtual-hand movement task. There were no observed long-term functional deficits due to the USEA implants. Conclusions Implantation of high-channel-count USEAs enables multi-degree-of-freedom control of virtual prosthetic hand movement and restoration of a rich selection of both proprioceptive and cutaneous sensory percepts spanning the hand during the short 4–5 week post-implant period. Future USEA use in longer-term implants and in closed-loop may enable restoration of many of the capabilities of an intact hand while contributing to a meaningful embodiment of the prosthesis. Electronic supplementary material The online version of this article (10.1186/s12984-017-0320-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Suzanne Wendelken
- Department of Bioengineering, University of Utah, Salt Lake City, UT, 84112, USA
| | - David M Page
- Department of Bioengineering, University of Utah, Salt Lake City, UT, 84112, USA
| | - Tyler Davis
- Department of Neurosurgery, University of Utah, Salt Lake City, UT, 84132, USA
| | - Heather A C Wark
- Department of Psychiatry, University of Utah, Salt Lake City, UT, 84102, USA
| | - David T Kluger
- Department of Bioengineering, University of Utah, Salt Lake City, UT, 84112, USA
| | - Christopher Duncan
- Division of Phys. Med. and Rehabilitation, University of Utah, Salt Lake City, UT, 84132, USA
| | - David J Warren
- Department of Bioengineering, University of Utah, Salt Lake City, UT, 84112, USA
| | | | - Gregory A Clark
- Department of Bioengineering, University of Utah, Salt Lake City, UT, 84112, USA.
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Kameda S, Hayashida Y, Tanaka Y, Akita D, Yagi T. A multichannel current stimulator chip for spatiotemporal pattern stimulation of neural tissues. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:5011-5. [PMID: 25571118 DOI: 10.1109/embc.2014.6944750] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We developed a prototype very-large-scale integration chip of a multichannel current stimulator for stimulating neural tissues by utilizing 0.25 μm high-voltage complementary metal-oxide-semiconductor technology. Our designed chip has 20 output channels that are driven by five current buffers arranged in parallel; each buffer controls four output channels in time-sharing mode. The amplitude of a stimulation pulse can be controlled within a range of approximately ±100 μA/phase in each output channel. The stimulus parameters, e.g., amplitude and duration, are controlled separately for each channel by digital codes stored in built-in registers. Combinations of anode and cathode electrodes to pass the current can be changed online. We integrated our stimulator chip with a multielectrode array and studied the neuronal responses to multichannel current stimulations with various temporal patterns in mouse brain slices.
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Xie X, Rieth L, Williams L, Negi S, Bhandari R, Caldwell R, Sharma R, Tathireddy P, Solzbacher F. Long-term reliability of Al2O3 and Parylene C bilayer encapsulated Utah electrode array based neural interfaces for chronic implantation. J Neural Eng 2014; 11:026016. [PMID: 24658358 DOI: 10.1088/1741-2560/11/2/026016] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE We focus on improving the long-term stability and functionality of neural interfaces for chronic implantation by using bilayer encapsulation. APPROACH We evaluated the long-term reliability of Utah electrode array (UEA) based neural interfaces encapsulated by 52 nm of atomic layer deposited Al2O3 and 6 µm of Parylene C bilayer, and compared these to devices with the baseline Parylene-only encapsulation. Three variants of arrays including wired, wireless, and active UEAs were used to evaluate this bilayer encapsulation scheme, and were immersed in phosphate buffered saline (PBS) at 57 °C for accelerated lifetime testing. MAIN RESULTS The median tip impedance of the bilayer encapsulated wired UEAs increased from 60 to 160 kΩ during the 960 days of equivalent soak testing at 37 °C, the opposite trend to that typically observed for Parylene encapsulated devices. The loss of the iridium oxide tip metallization and etching of the silicon tip in PBS solution contributed to the increase of impedance. The lifetime of fully integrated wireless UEAs was also tested using accelerated lifetime measurement techniques. The bilayer coated devices had stable power-up frequencies at ∼910 MHz and constant radio-frequency signal strength of -50 dBm during up to 1044 days (still under testing) of equivalent soaking time at 37 °C. This is a significant improvement over the lifetime of ∼100 days achieved with Parylene-only encapsulation at 37 °C. The preliminary samples of bilayer coated active UEAs with a flip-chip bonded ASIC chip had a steady current draw of ∼3 mA during 228 days of soak testing at 37 °C. An increase in the current draw has been consistently correlated to device failures, so is a sensitive metric for their lifetime. SIGNIFICANCE The trends of increasing electrode impedance of wired devices and performance stability of wireless and active devices support the significantly greater encapsulation performance of this bilayer encapsulation compared with Parylene-only encapsulation. The bilayer encapsulation should significantly improve the in vivo lifetime of neural interfaces for chronic implantation.
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Affiliation(s)
- Xianzong Xie
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, USA
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Xie X, Rieth L, Negi S, Bhandari R, Caldwell R, Sharma R, Tathireddy P, Solzbacher F. SELF ALIGNED TIP DEINSULATION OF ATOMIC LAYER DEPOSITED AL 2O 3 AND PARYLENE C COATED UTAH ELECTRODE ARRAY BASED NEURAL INTERFACES. JOURNAL OF MICROMECHANICS AND MICROENGINEERING : STRUCTURES, DEVICES, AND SYSTEMS 2014; 24:035003. [PMID: 24771981 PMCID: PMC3994722 DOI: 10.1088/0960-1317/24/3/035003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The recently developed alumina and Parylene C bi-layer encapsulation improved the lifetime of neural interfaces. Tip deinsulation of Utah electrode array based neural interfaces is challenging due to the complex 3D geometries and high aspect ratios of the devices. A three-step self-aligned process was developed for tip deinsulation of bilayer encapsulated arrays. The deinsulation process utilizes laser ablation to remove Parylene C, O2 reactive ion etching to remove carbon and Parylene residues, and buffered oxide etch to remove alumina deposited by atomic layer deposition, and expose the IrOx tip metallization. The deinsulated iridium oxide area was characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy to determine the morphology, surface morphology, composition, and electrical properties of the deposited layers and deinsulated tips. The alumina layer was found to prevent the formation of micro cracks on iridium oxide during the laser ablation process, which has been previously reported as a challenge for laser deinsulation of Parylene films. The charge injection capacity, charge storage capacity, and impedance of deinsulated iridium oxide were characterized to determine the deinsulation efficacy compared to Parylene-only insulation. Deinsulated iridium oxide with bilayer encapsulation had higher charge injection capacity (240 vs 320 nC) and similar electrochemical impedance (2.5 vs 2.5 kΩ) compared to deinsulated iridium oxide with only Parylene coating for an area of 2 × 10-4 cm2. Tip impedances were in the ranges of 20 to 50 kΩ, with median of 32 KΩ and standard deviation of 30 kΩ, showing the effectiveness of the self-aligned deinsulation process for alumina and Parylene C bi-layer encapsulation. The relatively uniform tip impedance values demonstrated the consistency of tip exposures.
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Affiliation(s)
- Xianzong Xie
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Loren Rieth
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Sandeep Negi
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | | | - Ryan Caldwell
- Department of Bioengineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Rohit Sharma
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Prashant Tathireddy
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA
| | - Florian Solzbacher
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112 USA ; Department of Bioengineering, University of Utah, Salt Lake City, UT 84112 USA
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Wark HAC, Sharma R, Mathews KS, Fernandez E, Yoo J, Christensen B, Tresco P, Rieth L, Solzbacher F, Normann RA, Tathireddy P. A new high-density (25 electrodes/mm²) penetrating microelectrode array for recording and stimulating sub-millimeter neuroanatomical structures. J Neural Eng 2013; 10:045003. [PMID: 23723133 DOI: 10.1088/1741-2560/10/4/045003] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Among the currently available neural interface devices, there has been a need for a penetrating electrode array with a high electrode-count and high electrode-density (the number of electrodes/mm(2)) that can be used for electrophysiological studies of sub-millimeter neuroanatomical structures. We have developed such a penetrating microelectrode array with both a high electrode-density (25 electrodes/mm(2)) and high electrode-count (up to 96 electrodes) for small nervous system structures, based on the existing Utah Slanted Electrode Array (USEA). Such high electrode-density arrays are expected to provide greater access to nerve fibers than the conventionally spaced USEA especially in small diameter nerves. APPROACH One concern for such high density microelectrode arrays is that they may cause a nerve crush-type injury upon implantation. We evaluated this possibility during acute (<10 h) in vivo experiments with electrode arrays implanted into small diameter peripheral nerves of anesthetized rats (sciatic nerve) and cats (pudendal nerve). MAIN RESULTS Successful intrafascicular implantation and viable nerve function was demonstrated via microstimulation, single-unit recordings and histological analysis. Measurements of the electrode impedances and quantified electrode dimensions demonstrated fabrication quality. The results of these experiments show that such high density neural interfaces can be implanted acutely into neural tissue without causing a complete nerve crush injury, while mediating intrafascicular access to fibers in small diameter peripheral nerves. SIGNIFICANCE This new penetrating microelectrode array has characteristics un-matched by other neural interface devices currently available for peripheral nervous system neurophysiological research.
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Affiliation(s)
- H A C Wark
- Department of Bioengineering, University of Utah, Salt Lake City, UT, USA
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Clark GA, Ledbetter NM, Warren DJ, Harrison RR. Recording sensory and motor information from peripheral nerves with Utah Slanted Electrode Arrays. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:4641-4. [PMID: 22255372 DOI: 10.1109/iembs.2011.6091149] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Recording and stimulation via high-count penetrating microelectrode arrays implanted in peripheral nerves may help restore precise motor and sensory function after nervous system damage or disease. Although previous work has demonstrated safety and relatively successful stimulation for long-term implants of 100-electrode Utah Slanted Electrode Arrays (USEAs) in feline sciatic nerve [1], two major remaining challenges were 1) to maintain viable recordings of nerve action potentials long-term, and 2) to overcome contamination of unit recordings by myoelectric (EMG) activity in awake, moving animals. In conjunction with improvements to USEAs themselves, we have redesigned several aspects of our USEA containment and connector systems. Although further increases in unit yield and long-term stability remain desirable, here we report considerable progress toward meeting both of these goals: We have successfully recorded unit activity from USEAs implanted intrafascicularly in sciatic nerve for periods up to 4 months (the terminal experimental time point), and we have developed a containment system that effectively eliminates or substantially reduces EMG contamination of unit recordings in the moving animal. In addition, we used a 100-channel wireless recording integrated circuit attached to implanted USEAs to transmit broadband or spike-threshold data from nerve. Neural data thusly obtained during imposed limb movements were decoded blindly to drive a virtual prosthetic limb in real time. These results support the possibility of using USEAs in peripheral nerves to provide motor control and cutaneous or proprioceptive sensory feedback in individuals after limb loss or spinal cord injury.
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Affiliation(s)
- Gregory A Clark
- Department of Bioengineering, School of Computing, University of Utah, Salt Lake City, UT 84112-9458, USA.
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Dowden BR, Frankel MA, Normann RA, Clark GA. Non-invasive method for selection of electrodes and stimulus parameters for FES applications with intrafascicular arrays. J Neural Eng 2011; 9:016006. [PMID: 22173566 DOI: 10.1088/1741-2560/9/1/016006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
High-channel-count intrafascicular electrode arrays provide comprehensive and selective access to the peripheral nervous system. One practical difficulty in using several electrode arrays to evoke coordinated movements in paralyzed limbs is the identification of the appropriate stimulation channels and stimulus parameters to evoke desired movements. Here we present the use of a six degree-of-freedom load cell placed under the foot of a feline to characterize the muscle activation produced by three 100-electrode Utah Slanted Electrode Arrays (USEAs) implanted into the femoral nerves, sciatic nerves, and muscular branches of the sciatic nerves of three cats. Intramuscular stimulation was used to identify the endpoint force directions produced by 15 muscles of the hind limb, and these directions were used to classify the forces produced by each intrafascicular USEA electrode as flexion or extension. For 451 USEA electrodes, stimulus intensities for threshold and saturation muscle forces were identified, and the 3D direction and linearity of the force recruitment curves were determined. Further, motor unit excitation independence for 198 electrode pairs was measured using the refractory technique. This study demonstrates the utility of 3D endpoint force monitoring as a simple and non-invasive metric for characterizing the muscle-activation properties of hundreds of implanted peripheral nerve electrodes, allowing for electrode and parameter selection for neuroprosthetic applications.
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Affiliation(s)
- B R Dowden
- Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA
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14
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John SE, Shivdasani MN, Leuenberger J, Fallon JB, Shepherd RK, Millard RE, Rathbone GD, Williams CE. An automated system for rapid evaluation of high-density electrode arrays in neural prostheses. J Neural Eng 2011; 8:036011. [PMID: 21493979 DOI: 10.1088/1741-2560/8/3/036011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The success of high-density electrode arrays for use in neural prostheses depends on efficient impedance monitoring and fault detection. Conventional methods of impedance testing and fault detection are time consuming and not always suited for in vivo assessment of high-density electrode arrays. Additionally, the ability to evaluate impedances and faults such as open and short circuits, both in vitro and in vivo, are important to ensure safe and effective stimulation. In this work we describe an automated system for the rapid evaluation of high-density electrode arrays. The system uses a current pulse similar to that used to stimulate neural tissue and measures the voltage across the electrode in order to calculate the impedance. The switching of the system was validated by emulating a high-density electrode array using light-emitting diodes and a resistor-capacitor network. The system was tested in vitro and in vivo using a range of commercially available and in-house developed electrode arrays. The system accurately identified faults in an 84-electrode array in less than 20 s and reliably measured impedances up to 110 kΩ using a 200 µA, 250 µs per phase current pulse. This system has direct application for screening high-density electrode arrays in both clinical and experimental settings.
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Affiliation(s)
- Sam E John
- The Bionic Ear Institute, Daly Wing, St Vincent's Hospital, VIC-3065, Australia
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15
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Ethier S, Sawan M. Exponential current pulse generation for efficient very high-impedance multisite stimulation. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2011; 5:30-38. [PMID: 23850976 DOI: 10.1109/tbcas.2010.2073707] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We describe in this paper an intracortical current-pulse generator for high-impedance microstimulation. This dual-chip system features a stimuli generator and a high-voltage electrode driver. The stimuli generator produces flexible rising exponential pulses in addition to standard rectangular stimuli. This novel stimulation waveform is expected to provide superior energy efficiency for action potential triggering while releasing less toxic reduced ions in the cortical tissues. The proposed fully integrated electrode driver is used as the output stage where high-voltage supplies are generated on-chip to significantly increase the voltage compliance for stimulation through high-impedance electrode-tissue interfaces. The stimuli generator has been implemented in 0.18-μm CMOS technology while a 0.8-μm CMOS/DMOS process has been used to integrate the high-voltage output stage. Experimental results show that the rectangular pulses cover a range of 1.6 to 167.2 μA with a DNL and an INL of 0.098 and 0.163 least-significant bit, respectively. The maximal dynamic range of the generated exponential reaches 34.36 dB at full scale within an error of ± 0.5 dB while all of its parameters (amplitude, duration, and time constant) are independently programmable over wide ranges. This chip consumes a maximum of 88.3 μ W in the exponential mode. High-voltage supplies of 8.95 and -8.46 V are generated by the output stage, boosting the voltage swing up to 13.6 V for a load as high as 100 kΩ.
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