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Woo BWK, Gott SC, Peck RA, Yan D, Rommelfanger MW, Rao MP. Ultrahigh Resolution Titanium Deep Reactive Ion Etching. ACS APPLIED MATERIALS & INTERFACES 2017; 9:20161-20168. [PMID: 28534392 DOI: 10.1021/acsami.6b16518] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Titanium (Ti) represents a promising new material for microelectromechanical systems (MEMS) because of its unique properties. Recently, this has been made possible with the advent of processes that enable deep reactive ion etching (DRIE) of high-aspect-ratio (HAR) structures in bulk Ti substrates. However, to date, these processes have been limited to minimum feature sizes (MFS) ≥750 nm. Although this is sufficient for many applications, MFS reduction to the deep submicrometer range opens potential for further device miniaturization and an opportunity for endowing devices with unique functionalities that are derived from precisely defined structures within this length scale regime. Herein, we report results from studies seeking to create means for realizing such opportunities through extension of Ti DRIE to the deep submicrometer scale. The effects of key process parameters on etch performance were investigated, and the understanding gained from these studies formed the development of a new ultrahigh resolution (UHR) Ti DRIE process. Using this process, we demonstrate, for the first time, fabrication of HAR structures in bulk Ti substrates with 150 nm MFS, smooth vertical sidewalls (88°), good etch rate (587 nm/min), and mask selectivity (11.1). This represents a fivefold or greater improvement in MFS relative to our previously reported processes and a 29-fold or greater improvement over more recent processes reported by others. As such, the UHR Ti DRIE process extends the state-of-the-art considerably, and it opens important new opportunities for Ti MEMS, particularly in the implantable medical device realm.
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Affiliation(s)
- Bryan W K Woo
- Department of Mechanical Engineering, ‡Center for Nanoscale Science and Engineering, §Central Facility for Advanced Microscopy and Microanalysis, ∥Department of Bioengineering, and ⊥Materials Science and Engineering Program, University of California, Riverside , Riverside, California 92521, United States
| | - Shannon C Gott
- Department of Mechanical Engineering, ‡Center for Nanoscale Science and Engineering, §Central Facility for Advanced Microscopy and Microanalysis, ∥Department of Bioengineering, and ⊥Materials Science and Engineering Program, University of California, Riverside , Riverside, California 92521, United States
| | - Ryan A Peck
- Department of Mechanical Engineering, ‡Center for Nanoscale Science and Engineering, §Central Facility for Advanced Microscopy and Microanalysis, ∥Department of Bioengineering, and ⊥Materials Science and Engineering Program, University of California, Riverside , Riverside, California 92521, United States
| | - Dong Yan
- Department of Mechanical Engineering, ‡Center for Nanoscale Science and Engineering, §Central Facility for Advanced Microscopy and Microanalysis, ∥Department of Bioengineering, and ⊥Materials Science and Engineering Program, University of California, Riverside , Riverside, California 92521, United States
| | - Mathias W Rommelfanger
- Department of Mechanical Engineering, ‡Center for Nanoscale Science and Engineering, §Central Facility for Advanced Microscopy and Microanalysis, ∥Department of Bioengineering, and ⊥Materials Science and Engineering Program, University of California, Riverside , Riverside, California 92521, United States
| | - Masaru P Rao
- Department of Mechanical Engineering, ‡Center for Nanoscale Science and Engineering, §Central Facility for Advanced Microscopy and Microanalysis, ∥Department of Bioengineering, and ⊥Materials Science and Engineering Program, University of California, Riverside , Riverside, California 92521, United States
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Khilwani R, Gilgunn PJ, Kozai TDY, Ong XC, Korkmaz E, Gunalan PK, Cui XT, Fedder GK, Ozdoganlar OB. Ultra-miniature ultra-compliant neural probes with dissolvable delivery needles: design, fabrication and characterization. Biomed Microdevices 2016; 18:97. [DOI: 10.1007/s10544-016-0125-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Microelectrode mapping of tonotopic, laminar, and field-specific organization of thalamo-cortical pathway in rat. Neuroscience 2016; 332:38-52. [PMID: 27329334 DOI: 10.1016/j.neuroscience.2016.06.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 05/17/2016] [Accepted: 06/13/2016] [Indexed: 11/20/2022]
Abstract
The rat has long been considered an important model system for studying neural mechanisms of auditory perception and learning, and particularly mechanisms involving auditory thalamo-cortical processing. However, the functional topography of the auditory thalamus, or medial geniculate body (MGB) has not yet been fully characterized in the rat, and the anatomically-defined features of field-specific, layer-specific and tonotopic thalamo-cortical projections have never been confirmed electrophysiologically. In the present study, we have established a novel technique for recording simultaneously from a surface microelectrode array on the auditory cortex, and a depth electrode array across auditory cortical layers and within the MGB, and characterized the rat MGB and thalamo-cortical projections under isoflurane anesthesia. We revealed that the ventral division of the MGB (MGv) exhibited a low-high-low CF gradient and long-short-long latency gradient along the dorsolateral-to-ventromedial axis, suggesting that the rat MGv is divided into two subdivisions. We also demonstrated that microstimulation in the MGv elicited cortical activation in layer-specific, region-specific and tonotopically organized manners. To our knowledge, the present study has provided the first and most compelling electrophysiological confirmation of the anatomical organization of the primary thalamo-cortical pathway in the rat, setting the groundwork for further investigation.
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Márton G, Baracskay P, Cseri B, Plósz B, Juhász G, Fekete Z, Pongrácz A. A silicon-based microelectrode array with a microdrive for monitoring brainstem regions of freely moving rats. J Neural Eng 2016; 13:026025. [PMID: 26924827 DOI: 10.1088/1741-2560/13/2/026025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Exploring neural activity behind synchronization and time locking in brain circuits is one of the most important tasks in neuroscience. Our goal was to design and characterize a microelectrode array (MEA) system specifically for obtaining in vivo extracellular recordings from three deep-brain areas of freely moving rats, simultaneously. The target areas, the deep mesencephalic reticular-, pedunculopontine tegmental-and pontine reticular nuclei are related to the regulation of sleep-wake cycles. APPROACH The three targeted nuclei are collinear, therefore a single-shank MEA was designed in order to contact them. The silicon-based device was equipped with 3 × 4 recording sites, located according to the geometry of the brain regions. Furthermore, a microdrive was developed to allow fine actuation and post-implantation relocation of the probe. The probe was attached to a rigid printed circuit board, which was fastened to the microdrive. A flexible cable was designed in order to provide not only electronic connection between the probe and the amplifier system, but sufficient freedom for the movements of the probe as well. MAIN RESULTS The microdrive was stable enough to allow precise electrode targeting into the tissue via a single track. The microelectrodes on the probe were suitable for recording neural activity from the three targeted brainstem areas. SIGNIFICANCE The system offers a robust solution to provide long-term interface between an array of precisely defined microelectrodes and deep-brain areas of a behaving rodent. The microdrive allowed us to fine-tune the probe location and easily scan through the regions of interest.
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Affiliation(s)
- G Márton
- Comparative Psychophysiology Department, Institute of Cognitive Neuroscience and Physiology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 2 Magyar Tudósok Blvd., H-1117, Budapest, Hungary. MEMS Laboratory, Institute for Technical Physics and Materials Science, Centre for Energy Research, Hungarian Academy of Sciences, 29-33 Konkoly Thege Miklós st., H-1121, Budapest, Hungary
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Scholten K, Meng E. Materials for microfabricated implantable devices: a review. LAB ON A CHIP 2015; 15:4256-72. [PMID: 26400550 DOI: 10.1039/c5lc00809c] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The application of microfabrication to the development of biomedical implants has produced a new generation of miniaturized technology for assisting treatment and research. Microfabricated implantable devices (μID) are an increasingly important tool, and the development of new μIDs is a rapidly growing field that requires new microtechnologies able to safely and accurately function in vivo. Here, we present a review of μID research that examines the critical role of material choice in design and fabrication. Materials commonly used for μID production are identified and presented along with their relevant physical properties and a survey of the state-of-the-art in μID development. The consequence of material choice as it pertains to microfabrication and biocompatibility is discussed in detail with a particular focus on the divide between hard, rigid materials and soft, pliable polymers.
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Affiliation(s)
- Kee Scholten
- Department of Biomedical Engineering, Univ. of Southern California, Los Angeles, CA 90089-1111, USA.
| | - Ellis Meng
- Department of Biomedical Engineering, Univ. of Southern California, Los Angeles, CA 90089-1111, USA.
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Gunasekera B, Saxena T, Bellamkonda R, Karumbaiah L. Intracortical recording interfaces: current challenges to chronic recording function. ACS Chem Neurosci 2015; 6:68-83. [PMID: 25587704 DOI: 10.1021/cn5002864] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Brain Computer Interfaces (BCIs) offer significant hope to tetraplegic and paraplegic individuals. This technology relies on extracting and translating motor intent to facilitate control of a computer cursor or to enable fine control of an external assistive device such as a prosthetic limb. Intracortical recording interfaces (IRIs) are critical components of BCIs and consist of arrays of penetrating electrodes that are implanted into the motor cortex of the brain. These multielectrode arrays (MEAs) are responsible for recording and conducting neural signals from local ensembles of neurons in the motor cortex with the high speed and spatiotemporal resolution that is required for exercising control of external assistive prostheses. Recent design and technological innovations in the field have led to significant improvements in BCI function. However, long-term (chronic) BCI function is severely compromised by short-term (acute) IRI recording failure. In this review, we will discuss the design and function of current IRIs. We will also review a host of recent advances that contribute significantly to our overall understanding of the cellular and molecular events that lead to acute recording failure of these invasive implants. We will also present recent improvements to IRI design and provide insights into the futuristic design of more chronically functional IRIs.
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Affiliation(s)
- Bhagya Gunasekera
- Regenerative
Bioscience Center, ADS Complex, The University of Georgia, Athens, Georgia 30602-2771, United States
| | - Tarun Saxena
- Wallace
H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0535, United States
| | - Ravi Bellamkonda
- Wallace
H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0535, United States
| | - Lohitash Karumbaiah
- Regenerative
Bioscience Center, ADS Complex, The University of Georgia, Athens, Georgia 30602-2771, United States
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Sommakia S, Lee HC, Gaire J, Otto KJ. Materials approaches for modulating neural tissue responses to implanted microelectrodes through mechanical and biochemical means. CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE 2014; 18:319-328. [PMID: 25530703 PMCID: PMC4267064 DOI: 10.1016/j.cossms.2014.07.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Implantable intracortical microelectrodes face an uphill struggle for widespread clinical use. Their potential for treating a wide range of traumatic and degenerative neural disease is hampered by their unreliability in chronic settings. A major factor in this decline in chronic performance is a reactive response of brain tissue, which aims to isolate the implanted device from the rest of the healthy tissue. In this review we present a discussion of materials approaches aimed at modulating the reactive tissue response through mechanical and biochemical means. Benefits and challenges associated with these approaches are analyzed, and the importance of multimodal solutions tested in emerging animal models are presented.
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Affiliation(s)
- Salah Sommakia
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-1791
| | - Heui C. Lee
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-1791
| | - Janak Gaire
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1791
| | - Kevin J. Otto
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-1791
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1791
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Ejserholm F, Köhler P, Granmo M, Schouenborg J, Bengtsson M, Wallman L. μ-Foil Polymer Electrode Array for Intracortical Neural Recordings. IEEE JOURNAL OF TRANSLATIONAL ENGINEERING IN HEALTH AND MEDICINE-JTEHM 2014; 2:1500207. [PMID: 27170864 PMCID: PMC4848100 DOI: 10.1109/jtehm.2014.2326859] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 04/09/2014] [Accepted: 05/05/2013] [Indexed: 11/13/2022]
Abstract
We
have developed a multichannel electrode array—termed \documentclass[12pt]{minimal}
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}{}\(\mu \) \end{document}-foil—that comprises ultrathin
and flexible electrodes protruding from a thin foil at fixed distances. In
addition to allowing some of the active sites to reach less compromised tissue,
the barb-like protrusions that also serves the purpose of anchoring the electrode
array into the tissue. This paper is an early evaluation of technical aspects
and performance of this electrode array in acute in vitro/in
vivo experiments. The interface impedance was reduced by up to two
decades by electroplating the active sites with platinum black. The platinum
black also allowed for a reduced phase lag for higher frequency components.
The distance between the protrusions of the electrode array was tailored to
match the architecture of the rat cerebral cortex. In vivo acute
measurements confirmed a high signal-to-noise ratio for the neural recordings,
and no significant crosstalk between recording channels.
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Gabran SRI, Salam MT, Dian J, El-Hayek Y, Perez Velazquez JL, Genov R, Carlen PL, Salama MMA, Mansour RR. High-density intracortical microelectrode arrays with multiple metallization layers for fine-resolution neuromonitoring and neurostimulation. IEEE Trans Neural Syst Rehabil Eng 2013; 21:869-79. [PMID: 24122564 DOI: 10.1109/tnsre.2013.2279403] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Intracortical microelectrodes play a prominent role in the operation of neural interfacing systems. They provide an interface for recording neural activities and modulating their behavior through electric stimulation. The performance of such systems is thus directly meliorated by advances in electrode technology. We present a new architecture for intracortical electrodes designed to increase the number of recording/stimulation channels for a given set of shank dimensions. The architecture was implemented on silicon using microfabrication process and fabricated 3-mm-long electrode shanks with six relatively large (110 μm ×110 μm) pads in each shank for electrographic signal recording to detect important precursors with potential clinical relevance and electrical stimulation to correct neural behavior with low-power dissipation in an implantable device. Moreover, an electrode mechanical design was developed to increase its stiffness and reduce shank deflection to improve spatial accuracy during an electrode implantation. Furthermore, the pads were post-processed using pulsated low current electroplating and reduced their impedances by ≈ 30 times compared to the traditionally fabricated pads. The paper also presents microfabrication process, electrodes characterization, comparison to the commercial equivalents, and in vitro and in vivo validations.
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McCarthy PT, Otto KJ, Rao MP. Robust penetrating microelectrodes for neural interfaces realized by titanium micromachining. Biomed Microdevices 2011; 13:503-15. [PMID: 21360044 PMCID: PMC3085117 DOI: 10.1007/s10544-011-9519-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Neural prosthetic interfaces based upon penetrating microelectrode devices have broadened our understanding of the brain and have shown promise for restoring neurological functions lost to disease, stroke, or injury. However, the eventual viability of such devices for use in the treatment of neurological dysfunction may be ultimately constrained by the intrinsic brittleness of silicon, the material most commonly used for manufacture of penetrating microelectrodes. This brittleness creates predisposition for catastrophic fracture, which may adversely affect the reliability and safety of such devices, due to potential for fragmentation within the brain. Herein, we report the development of titanium-based penetrating microelectrodes that seek to address this potential future limitation. Titanium provides advantage relative to silicon due to its superior fracture toughness, which affords potential for creation of robust devices that are resistant to catastrophic failure. Realization of these devices is enabled by recently developed techniques which provide opportunity for fabrication of high-aspect-ratio micromechanical structures in bulk titanium substrates. Details are presented regarding the design, fabrication, mechanical testing, in vitro functional characterization, and preliminary in vivo testing of devices intended for acute recording in rat auditory cortex and thalamus, both independently and simultaneously.
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Affiliation(s)
- Patrick T McCarthy
- School of Mechanical Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
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