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Wettability and Surface Roughness of Parylene C on Three-Dimensional-Printed Photopolymers. MATERIALS 2022; 15:ma15124159. [PMID: 35744218 PMCID: PMC9228345 DOI: 10.3390/ma15124159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 06/02/2022] [Accepted: 06/09/2022] [Indexed: 11/21/2022]
Abstract
The use of poly-(para-chloro-xylylene) (Parylene C) in microelectromechanical systems and medical devices has increased rapidly. However, little research has been conducted on the wettability and surface roughness of Parylene C after being soaked in solutions. In this study, the contact angle and surface roughness (arithmetic average of roughness) of Parylene C on three-dimensional (3D)-printed photopolymer in 10% sodium hydroxide, 10% ammonium hydroxide, and 100% phosphate-buffered saline (PBS) solutions were investigated using a commercial contact angle measurement system and laser confocal microscope, respectively. The collected data indicated that 10% ammonium hydroxide had no major effect on the contact angle of Parylene C on a substrate, with a Shore A hardness of 50. However, 10% sodium hydroxide, 10% ammonium hydroxide, and 100% PBS considerably affected the contact angle of Parylene C on a substrate with a Shore A hardness of 85. Substrates with Parylene C coating exhibited lower surface roughness than uncoated substrates. The substrates coated with Parylene C that were soaked in 10% ammonium hydroxide exhibited high surface roughness. The aforementioned results indicate that 3D-printed photopolymers coated with Parylene C can offer potential benefits when used in biocompatible devices.
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Zia M, Chung B, Sober S, Bakir MS. Flexible Multielectrode Arrays With 2-D and 3-D Contacts for In Vivo Electromyography Recording. IEEE TRANSACTIONS ON COMPONENTS, PACKAGING, AND MANUFACTURING TECHNOLOGY 2020; 10:197-202. [PMID: 32280561 PMCID: PMC7150534 DOI: 10.1109/tcpmt.2019.2963556] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We present a system for recording in vivo electromyographic (EMG) signals from songbirds using hybrid polyimide-polydimethylsiloxane (PDMS) flexible multielectrode arrays (MEAs). 2-D electrodes with a diameter of 200, 125, and 50 μm and a center-to-center pitch of 300, 200, and 100 μm, respectively, were fabricated. 3-D MEAs were fabricated using a photoresist reflow process to obtain hemispherical domes utilized to form the 3-D electrodes. Biocompatibility and flexibility of the arrays were ensured by using polyimide and PDMS as the materials of choice for the arrays. EMG activity was recorded from the expiratory muscle group of anesthetized songbirds using the fabricated 2-D and 3-D arrays. Air pressure data were also recorded simultaneously from the air sac of the songbird. Together, EMG recordings and air pressure measurements can be used to characterize how the nervous system controls breathing and other motor behaviors. Such technologies can in turn provide unique insights into motor control in a range of species, including humans. An improvement of over 7× in the signal-to-noise ratio (SNR) is observed with the utilization of 3-D MEAs in comparison to 2-D MEAs.
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Affiliation(s)
- Muneeb Zia
- Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA
| | - Bryce Chung
- Department of Biology, Emory University, Atlanta, GA 30322 USA
| | - Samuel Sober
- Department of Biology, Emory University, Atlanta, GA 30322 USA
| | - Muhannad S Bakir
- Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA
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Zia M, Chung B, Sober SJ, Bakir MS. Fabrication and Characterization of 3D Multi-Electrode Array on Flexible Substrate for In Vivo EMG Recording from Expiratory Muscle of Songbird. TECHNICAL DIGEST. INTERNATIONAL ELECTRON DEVICES MEETING 2018; 2018:29.4.1-29.4.4. [PMID: 30846889 PMCID: PMC6400221 DOI: 10.1109/iedm.2018.8614503] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This work presents fabrication and characterization of flexible three-dimensional (3D) multi-electrode arrays (MEAs) capable of high signal-to-noise (SNR) electromyogram (EMG) recordings from the expiratory muscle of a songbird. The fabrication utilizes a photoresist reflow process to obtain 3D structures to serve as the electrodes. A polyimide base with a PDMS top insulation was utilized to ensure flexibility and biocompatibility of the fabricated 3D MEA devices. SNR measurements from the fabricated 3D electrode show up to a 7x improvement as compared to the 2D MEAs.
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Affiliation(s)
- Muneeb Zia
- Georgia Institute of Technology, Atlanta, GA, USA,
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Garcia-Sandoval A, Pal A, Mishra AM, Sherman S, Parikh AR, Joshi-Imre A, Arreaga-Salas D, Gutierrez-Heredia G, Duran-Martinez AC, Nathan J, Hosseini SM, Carmel JB, Voit W. Chronic softening spinal cord stimulation arrays. J Neural Eng 2018; 15:045002. [PMID: 29569573 DOI: 10.1088/1741-2552/aab90d] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE We sought to develop a cervical spinal cord stimulator for the rat that is durable, stable, and does not perturb the underlying spinal cord. APPROACH We created a softening spinal cord stimulation (SCS) array made from shape memory polymer (SMP)-based flexible electronics. We developed a new photolithographic process to pattern high surface area titanium nitride (TiN) electrodes onto gold (Au) interconnects. The thiol-ene acrylate polymers are stiff at room temperature and soften following implantation into the body. Durability was measured by the duration the devices produced effective stimulation and by accelerated aging in vitro. Stability was measured by the threshold to provoke an electromyogram (EMG) muscle response and by measuring impedance using electrochemical impedance spectroscopy (EIS). In addition, spinal cord modulation of motor cortex potentials was measured. The spinal column and implanted arrays were imaged with MRI ex vivo, and histology for astrogliosis and immune reaction was performed. MAIN RESULTS For durability, the design of the arrays was modified over three generations to create an array that demonstrated activity up to 29 weeks. SCS arrays showed no significant degradation over a simulated 29 week period of accelerated aging. For stability, the threshold for provoking an EMG rose in the first few weeks and then remained stable out to 16 weeks; the impedance showed a similar rise early with stability thereafter. Spinal cord stimulation strongly enhanced motor cortex potentials throughout. Upon explantation, device performance returned to pre-implant levels, indicating that biotic rather than abiotic processes were the cause of changing metrics. MRI and histology showed that softening SCS produced less tissue deformation than Parylene-C arrays. There was no significant astrogliosis or immune reaction to either type of array. SIGNIFICANCE Softening SCS arrays meet the needs for research-grade devices in rats and could be developed into human devices in the future.
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Affiliation(s)
- Aldo Garcia-Sandoval
- Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX 75080, United States of America
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Cuellar CA, Mendez AA, Islam R, Calvert JS, Grahn PJ, Knudsen B, Pham T, Lee KH, Lavrov IA. The Role of Functional Neuroanatomy of the Lumbar Spinal Cord in Effect of Epidural Stimulation. Front Neuroanat 2017; 11:82. [PMID: 29075183 PMCID: PMC5642185 DOI: 10.3389/fnana.2017.00082] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 09/07/2017] [Indexed: 01/07/2023] Open
Abstract
In this study, the neuroanatomy of the swine lumbar spinal cord, particularly the spatial orientation of dorsal roots was correlated to the anatomical landmarks of the lumbar spine and to the magnitude of motor evoked potentials during epidural electrical stimulation (EES). We found that the proximity of the stimulating electrode to the dorsal roots entry zone across spinal segments was a critical factor to evoke higher peak-to-peak motor responses. Positioning the electrode close to the dorsal roots produced a significantly higher impact on motor evoked responses than rostro-caudal shift of electrode from segment to segment. Based on anatomical measurements of the lumbar spine and spinal cord, significant differences were found between L1-L4 to L5-L6 segments in terms of spinal cord gross anatomy, dorsal roots and spine landmarks. Linear regression analysis between intersegmental landmarks was performed and L2 intervertebral spinous process length was selected as the anatomical reference in order to correlate vertebral landmarks and the spinal cord structures. These findings present for the first time, the influence of spinal cord anatomy on the effects of epidural stimulation and the role of specific orientation of electrodes on the dorsal surface of the dura mater in relation to the dorsal roots. These results are critical to consider as spinal cord neuromodulation strategies continue to evolve and novel spinal interfaces translate into clinical practice.
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Affiliation(s)
- Carlos A Cuellar
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | - Aldo A Mendez
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | - Riazul Islam
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | - Jonathan S Calvert
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo ClinicRochester, MN, United States
| | - Peter J Grahn
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | - Bruce Knudsen
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | - Tuan Pham
- Department of Biological Sciences, Lehigh UniversityBethlehem, PA, United States
| | - Kendall H Lee
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States.,Department of Physical Medicine and Rehabilitation, Mayo ClinicRochester, MN, United States.,Department of Physiology and Biomedical Engineering, Mayo ClinicRochester, MN, United States
| | - Igor A Lavrov
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States.,Department of Physiology and Biomedical Engineering, Mayo ClinicRochester, MN, United States.,Institute of Fundamental Medicine and Biology, Kazan Federal UniversityKazan, Russia
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Lavrov I, Gerasimenko Y, Burdick J, Zhong H, Roy RR, Edgerton VR. Integrating multiple sensory systems to modulate neural networks controlling posture. J Neurophysiol 2015; 114:3306-14. [PMID: 26445868 DOI: 10.1152/jn.00583.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/05/2015] [Indexed: 01/03/2023] Open
Abstract
In this study we investigated the ability of sensory input to produce tonic responses in hindlimb muscles to facilitate standing in adult spinal rats and tested two hypotheses: 1) whether the spinal neural networks below a complete spinal cord transection can produce tonic reactions by activating different sensory inputs and 2) whether facilitation of tonic and rhythmic responses via activation of afferents and with spinal cord stimulation could engage similar neuronal mechanisms. We used a dynamically controlled platform to generate vibration during weight bearing, epidural stimulation (at spinal cord level S1), and/or tail pinching to determine the postural control responses that can be generated by the lumbosacral spinal cord. We observed that a combination of platform displacement, epidural stimulation, and tail pinching produces a cumulative effect that progressively enhances tonic responses in the hindlimbs. Tonic responses produced by epidural stimulation alone during standing were represented mainly by monosynaptic responses, whereas the combination of epidural stimulation and tail pinching during standing or epidural stimulation during stepping on a treadmill facilitated bilaterally both monosynaptic and polysynaptic responses. The results demonstrate that tonic muscle activity after complete spinal cord injury can be facilitated by activation of specific combinations of afferent inputs associated with load-bearing proprioception and cutaneous input in the presence of epidural stimulation and indicate that whether activation of tonic or rhythmic responses is generated depends on the specific combinations of sources and types of afferents activated in the hindlimb muscles.
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Affiliation(s)
- I Lavrov
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and
| | - Y Gerasimenko
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Pavlov Institute of Physiology, St. Petersburg, Russia; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and
| | - J Burdick
- Bioengineering, California Institute of Technology, Pasadena, California
| | - H Zhong
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California
| | - R R Roy
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California
| | - V R Edgerton
- Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California
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Chang CW, Lo YK, Gad P, Edgerton R, Liu W. Design and fabrication of a multi-electrode array for spinal cord epidural stimulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:6834-7. [PMID: 25571566 DOI: 10.1109/embc.2014.6945198] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A detailed design, fabrication, characterization and test of a flexible multi-site platinum/polyimide based electrode array for electrical epidural stimulation in spinal cord prosthesis is described in this paper. Carefully designed 8.4 μm-thick structure fabrication flow achieves an electrode surface modification with 3.8 times enhanced effective surface area without extra process needed. Measured impedance and phase of two type of electrodes are 2.35±0.21 KΩ and 2.10±0.11 KΩ, -34.25±8.07° and -27.71±8.27° at 1K Hz, respectively. The fabricated arrays were then in-vitro tested by a multichannel neural stimulation system in physiological saline to validate the capability for electrical stimulation. The measured channel isolation on adjacent electrode is about -34dB. Randles cell model was used to investigate the charging waveforms, the model parameters were then extracted by various methods. The measured charge transfer resistance, double layer capacitance, and solution resistance are 1.9 KΩ, 220 nF and 15 KΩ, respectively. The results show that the fabricated array is applicable for electrical stimulation with well characterized parameters. Combined with a multichannel stimulator, this system provides a full solution for versatile neural stimulation applications.
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Gad P, Roy RR, Choe J, Zhong H, Nandra MS, Tai YC, Gerasimenko Y, Edgerton VR. Electrophysiological mapping of rat sensorimotor lumbosacral spinal networks after complete paralysis. PROGRESS IN BRAIN RESEARCH 2015; 218:199-212. [PMID: 25890138 DOI: 10.1016/bs.pbr.2015.01.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Stimulation of the spinal cord has been shown to have great potential for improving function after motor deficits caused by injury or pathological conditions. Using a wide range of animal models, many studies have shown that stimulation applied to the neural networks intrinsic to the spinal cord can result in a dramatic improvement of motor ability, even allowing an animal to step and stand after a complete spinal cord transection. Clinical use of this technology, however, has been slow to develop due to the invasive nature of the implantation procedures and the difficulty of ascertaining specific sites of stimulation that would provide optimal amelioration of the motor deficits. Moreover, the development of tools available to control precise stimulation chronically via biocompatible electrodes has been limited. In this chapter, we outline the use of a multisite electrode array in the spinal rat model to identify and stimulate specific sites of the spinal cord to produce discrete motor behaviors in spinal rats. The results demonstrate that spinal rats can stand and step when the spinal cord is stimulated tonically via electrodes located at specific sites on the spinal cord. The quality of stepping and standing was dependent on the location of the electrodes on the spinal cord, the specific stimulation parameters, and the orientation of the cathode and anode. The spinal motor evoked potentials in selected muscles during standing and stepping are shown to be critical tools to study selective activation of interneuronal circuits via responses of varying latencies. The present results provide further evidence that the assessment of functional networks in the background of behaviorally relevant functional states is likely to be a physiological tool of considerable importance in developing strategies to facilitate recovery of motor function after a number of neuromotor disorders.
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Affiliation(s)
- Parag Gad
- Departments of Integrative Biology and Physiology, University of California, Los Angeles, CA, USA
| | - Roland R Roy
- Departments of Integrative Biology and Physiology, University of California, Los Angeles, CA, USA; Brain Research Institute, University of California, Los Angeles, CA, USA
| | - Jaehoon Choe
- Departments of Integrative Biology and Physiology, University of California, Los Angeles, CA, USA; Department of Neuroscience, University of California, Los Angeles, CA, USA
| | - Hui Zhong
- Departments of Integrative Biology and Physiology, University of California, Los Angeles, CA, USA
| | | | - Yu-Chong Tai
- Department of Electrical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Yury Gerasimenko
- Departments of Integrative Biology and Physiology, University of California, Los Angeles, CA, USA; Pavlov Institute of Physiology, St. Petersburg, Russia; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia
| | - V Reggie Edgerton
- Departments of Integrative Biology and Physiology, University of California, Los Angeles, CA, USA; Department of Neurobiology, University of California, Los Angeles, CA, USA; Department of Neurosurgery, University of California, Los Angeles, CA, USA; Brain Research Institute, University of California, Los Angeles, CA, USA.
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Gad P, Choe J, Nandra MS, Zhong H, Roy RR, Tai YC, Edgerton VR. Development of a multi-electrode array for spinal cord epidural stimulation to facilitate stepping and standing after a complete spinal cord injury in adult rats. J Neuroeng Rehabil 2013; 10:2. [PMID: 23336733 PMCID: PMC3599040 DOI: 10.1186/1743-0003-10-2] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 01/07/2013] [Indexed: 01/07/2023] Open
Abstract
Background Stimulation of the spinal cord has been shown to have great potential for improving function after motor deficits caused by injury or pathological conditions. Using a wide range of animal models, many studies have shown that stimulation applied to the neural networks intrinsic to the spinal cord can result in a dramatic improvement of motor ability, even allowing an animal to step and stand after a complete spinal cord transection. Clinical use of this technology, however, has been slow to develop due to the invasive nature of the implantation procedures, the lack of versatility in conventional stimulation technology, and the difficulty of ascertaining specific sites of stimulation that would provide optimal amelioration of the motor deficits. Moreover, the development of tools available to control precise stimulation chronically via biocompatible electrodes has been limited. In this paper, we outline the development of this technology and its use in the spinal rat model, demonstrating the ability to identify and stimulate specific sites of the spinal cord to produce discrete motor behaviors in spinal rats using this array. Methods We have designed a chronically implantable, rapidly switchable, high-density platinum based multi-electrode array that can be used to stimulate at 1–100 Hz and 1–10 V in both monopolar and bipolar configurations to examine the electrophysiological and behavioral effects of spinal cord epidural stimulation in complete spinal cord transected rats. Results In this paper, we have demonstrated the effectiveness of using high-resolution stimulation parameters in the context of improving motor recovery after a spinal cord injury. We observed that rats whose hindlimbs were paralyzed can stand and step when specific sets of electrodes of the array are stimulated tonically (40 Hz). Distinct patterns of stepping and standing were produced by stimulation of different combinations of electrodes on the array located at specific spinal cord levels and by specific stimulation parameters, i.e., stimulation frequency and intensity, and cathode/anode orientation. The array also was used to assess functional connectivity between the cord dorsum to interneuronal circuits and specific motor pools via evoked potentials induced at 1 Hz stimulation in the absence of any anesthesia. Conclusions Therefore the high density electrode array allows high spatial resolution and the ability to selectively activate different neural pathways within the lumbosacral region of the spinal cord to facilitate standing and stepping in adult spinal rats and provides the capability to evoke motor potentials and thus a means for assessing connectivity between sensory circuits and specific motor pools and muscles.
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Affiliation(s)
- Parag Gad
- Biomedical Engineering IDP, University of California, Los Angeles, CA 90095, USA
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