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Jakešová M, Kunovský O, Gablech I, Khodagholy D, Gelinas J, Głowacki ED. Coupling of photovoltaics with neurostimulation electrodes-optical to electrolytic transduction. J Neural Eng 2024; 21:046003. [PMID: 38885680 DOI: 10.1088/1741-2552/ad593d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 06/17/2024] [Indexed: 06/20/2024]
Abstract
Objective.The wireless transfer of power for driving implantable neural stimulation devices has garnered significant attention in the bioelectronics field. This study explores the potential of photovoltaic (PV) power transfer, utilizing tissue-penetrating deep-red light-a novel and promising approach that has received less attention compared to traditional induction or ultrasound techniques. Our objective is to critically assess key parameters for directly powering neurostimulation electrodes with PVs, converting light impulses into neurostimulation currents.Approach.We systematically investigate varying PV cell size, optional series configurations, and coupling with microelectrodes fabricated from a range of materials such as Pt, TiN, IrOx, Ti, W, PtOx, Au, or poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate). Additionally, two types of PVs, ultrathin organic PVs and monocrystalline silicon PVs, are compared. These combinations are employed to drive pairs of electrodes with different sizes and impedances. The readout method involves measuring electrolytic current using a straightforward amplifier circuit.Main results.Optimal PV selection is crucial, necessitating sufficiently large PV cells to generate the desired photocurrent. Arranging PVs in series is essential to produce the appropriate voltage for driving current across electrode/electrolyte impedances. By carefully choosing the PV arrangement and electrode type, it becomes possible to emulate electrical stimulation protocols in terms of charge and frequency. An important consideration is whether the circuit is photovoltage-limited or photocurrent-limited. High charge-injection capacity electrodes made from pseudo-faradaic materials impose a photocurrent limit, while more capacitive materials like Pt are photovoltage-limited. Although organic PVs exhibit lower efficiency than silicon PVs, in many practical scenarios, stimulation current is primarily limited by the electrodes rather than the PV driver, leading to potential parity between the two types.Significance.This study provides a foundational guide for designing a PV-powered neurostimulation circuit. The insights gained are applicable to bothin vitroandin vivoapplications, offering a resource to the neural engineering community.
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Affiliation(s)
- Marie Jakešová
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Ondřej Kunovský
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Imrich Gablech
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
| | - Dion Khodagholy
- Department of Electrical Engineering, Columbia University, New York, NY 10027, United States of America
| | - Jennifer Gelinas
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, United States of America
- Department of Neurology, Columbia University, New York, NY 10032, United States of America
| | - Eric Daniel Głowacki
- Bioelectronics Materials and Devices Laboratory, Central European Institute of Technology CEITEC, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
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Landari H, Messaddeq Y, Miled A. Microscope-FTIR Spectrometry Based Sensor for Neurotransmitters Detection. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2021; 15:938-948. [PMID: 34432634 DOI: 10.1109/tbcas.2021.3107805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In this work, we present a new sensing approach for aqueous samples based on the microscope-FTIR spectrometer and applied for neurotransmitters. Our contribution in this work consists of a new sample handling system for the microscope-FTIR spectrometer based on a total reflective mirror, a heated hydrophobic layer for solvent removal/evaporation and sample confinement and a microfluidic system that handles sample injection unlike standard sample handling system which was based only on a total reflective mirror. In addition, another part of our contribution consists of proposing a new algorithm to extract molecular composition of the solution with high estimation ratios and based on the analysis of detected peaks on IR spectra. The data acquired from the microscope-FTIR spectrometer was analyzed by a newly developed algorithm to identify each neurotransmitter in homogeneous and non-homogeneous solutions with high selectivity. We used six neurotransmitter molecules (Dopamine hydrochloride, L-Ascorbic acid, Acetylcholine chloride, y-Aminobutyric, Glycine and L-Glutamic acid). The results obtained based on the algorithm developed showed that, using the new system, the six neurotransmitters can be identified in homogeneous and mixture solutions with an estimation ratio range of 88.8%-100% for Dopamine hydrochloride, 80%-100% for L-Ascorbic acid, 75%-100% for Acetylcholine chloride, 75%-100% for L-Glutamic, 77.7%-100% for y-Aminobutyric and 75%-100% for Glycine.
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Wellman SM, Eles JR, Ludwig KA, Seymour JP, Michelson NJ, McFadden WE, Vazquez AL, Kozai TDY. A Materials Roadmap to Functional Neural Interface Design. ADVANCED FUNCTIONAL MATERIALS 2018; 28:1701269. [PMID: 29805350 PMCID: PMC5963731 DOI: 10.1002/adfm.201701269] [Citation(s) in RCA: 181] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Advancement in neurotechnologies for electrophysiology, neurochemical sensing, neuromodulation, and optogenetics are revolutionizing scientific understanding of the brain while enabling treatments, cures, and preventative measures for a variety of neurological disorders. The grand challenge in neural interface engineering is to seamlessly integrate the interface between neurobiology and engineered technology, to record from and modulate neurons over chronic timescales. However, the biological inflammatory response to implants, neural degeneration, and long-term material stability diminish the quality of interface overtime. Recent advances in functional materials have been aimed at engineering solutions for chronic neural interfaces. Yet, the development and deployment of neural interfaces designed from novel materials have introduced new challenges that have largely avoided being addressed. Many engineering efforts that solely focus on optimizing individual probe design parameters, such as softness or flexibility, downplay critical multi-dimensional interactions between different physical properties of the device that contribute to overall performance and biocompatibility. Moreover, the use of these new materials present substantial new difficulties that must be addressed before regulatory approval for use in human patients will be achievable. In this review, the interdependence of different electrode components are highlighted to demonstrate the current materials-based challenges facing the field of neural interface engineering.
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Affiliation(s)
- Steven M Wellman
- Department of Bioengineering, Center for the Basis of Neural Cognition, McGowan Institute of Regenerative Medicine, NeuroTech Center, University of Pittsburgh Brain Institute, Center for Neuroscience at the University of Pittsburgh, University of Pittsburgh, 208 Center for Biotechnology, 300 Technology Dr., Pittsburgh, PA 15219, United States
| | - James R Eles
- Department of Bioengineering, Center for the Basis of Neural Cognition, McGowan Institute of Regenerative Medicine, NeuroTech Center, University of Pittsburgh Brain Institute, Center for Neuroscience at the University of Pittsburgh, University of Pittsburgh, 208 Center for Biotechnology, 300 Technology Dr., Pittsburgh, PA 15219, United States
| | - Kip A Ludwig
- Department of Neurologic Surgery, 200 First St. SW, Rochester, MN 55905
| | - John P Seymour
- Electrical & Computer Engineering, 1301 Beal Ave., 2227 EECS, Ann Arbor, MI 48109
| | - Nicholas J Michelson
- Department of Bioengineering, Center for the Basis of Neural Cognition, McGowan Institute of Regenerative Medicine, NeuroTech Center, University of Pittsburgh Brain Institute, Center for Neuroscience at the University of Pittsburgh, University of Pittsburgh, 208 Center for Biotechnology, 300 Technology Dr., Pittsburgh, PA 15219, United States
| | - William E McFadden
- Department of Bioengineering, Center for the Basis of Neural Cognition, McGowan Institute of Regenerative Medicine, NeuroTech Center, University of Pittsburgh Brain Institute, Center for Neuroscience at the University of Pittsburgh, University of Pittsburgh, 208 Center for Biotechnology, 300 Technology Dr., Pittsburgh, PA 15219, United States
| | - Alberto L Vazquez
- Department of Bioengineering, Center for the Basis of Neural Cognition, McGowan Institute of Regenerative Medicine, NeuroTech Center, University of Pittsburgh Brain Institute, Center for Neuroscience at the University of Pittsburgh, University of Pittsburgh, 208 Center for Biotechnology, 300 Technology Dr., Pittsburgh, PA 15219, United States
| | - Takashi D Y Kozai
- Department of Bioengineering, Center for the Basis of Neural Cognition, McGowan Institute of Regenerative Medicine, NeuroTech Center, University of Pittsburgh Brain Institute, Center for Neuroscience at the University of Pittsburgh, University of Pittsburgh, 208 Center for Biotechnology, 300 Technology Dr., Pittsburgh, PA 15219, United States
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Celinskis D, Towe BC. Wireless impedance measurements for monitoring peripheral vascular disease. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:6937-40. [PMID: 25571591 DOI: 10.1109/embc.2014.6945223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Wireless microdevices powered by ultrasound energy have been fabricated to measure and telemeter tissue impedance spectrums for applications in peripheral vascular disease monitoring. The system is characterized by simplicity of the implant consisting of only two electrical components. Ex vivo testing shows the potential for constructing tissue impedance spectrum plots over the range from 10 Hz to 10 kHz by a device less than 1 mm in diameter and 1 cm long. The neurostimulator microdevice was powered by continuous waveform 650 kHz ultrasound with a swept-frequency amplitude modulation. The system was operated at safe ultrasound power levels on the order of 10-100 mW/cm(2). The device proved to be sensitive and able to measure tissue impedances over a broad range. Volume conducted signals carrying impedance information from the microdevice were remotely detected by surface biopotential electrodes.
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Li X, Serdijn WA, Zheng W, Tian Y, Zhang B. The injectable neurostimulator: an emerging therapeutic device. Trends Biotechnol 2015; 33:388-94. [PMID: 25921343 DOI: 10.1016/j.tibtech.2015.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 12/14/2022]
Abstract
Injectable neurostimulators are currently applied in clinical trials to minimize the side effects such as discomfort, risk of infection, and post-surgery trauma, which can be pronounced with conventional, bulky implantable neurostimulators. Owing to its smaller size, wireless-updatable software, and wireless power supply, the injectable neurostimulator is presumably less invasive, 'smarter', and has a longer lifetime. We discuss the concept and development of the injectable neurostimulator, persistent implementation challenges, and obstacles to be overcome in its evolution. We survey the use of new materials, technologies, and design methods for injectable electrodes, batteries, antennas, and packaging to enhance reliability and other features. These advances in the field are accompanied by progress in electrophysiology, neuroscience, neurology, clinical trials, and treatments.
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Affiliation(s)
- Xiaolong Li
- School of Electronics and Information, Jiangsu University of Science and Technology, Zhenjiang, China.
| | - Wouter A Serdijn
- Section of Bioelectronics, Delft University of Technology, Delft, the Netherlands
| | - Wei Zheng
- School of Electronics and Information, Jiangsu University of Science and Technology, Zhenjiang, China
| | - Yubo Tian
- School of Electronics and Information, Jiangsu University of Science and Technology, Zhenjiang, China
| | - Bing Zhang
- School of Electronics and Information, Jiangsu University of Science and Technology, Zhenjiang, China
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Giszter SF. Spinal primitives and intra-spinal micro-stimulation (ISMS) based prostheses: a neurobiological perspective on the "known unknowns" in ISMS and future prospects. Front Neurosci 2015; 9:72. [PMID: 25852454 PMCID: PMC4367173 DOI: 10.3389/fnins.2015.00072] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 02/18/2014] [Indexed: 11/13/2022] Open
Abstract
The current literature on Intra-Spinal Micro-Stimulation (ISMS) for motor prostheses is reviewed in light of neurobiological data on spinal organization, and a neurobiological perspective on output motor modularity, ISMS maps, stimulation combination effects, and stability. By comparing published data in these areas, the review identifies several gaps in current knowledge that are crucial to the development of effective intraspinal neuroprostheses. Gaps can be categorized into a lack of systematic and reproducible details of: (a) Topography and threshold for ISMS across the segmental motor system, the topography of autonomic recruitment by ISMS, and the coupling relations between these two types of outputs in practice. (b) Compositional rules for ISMS motor responses tested across the full range of the target spinal topographies. (c) Rules for ISMS effects' dependence on spinal cord state and neural dynamics during naturally elicited or ISMS triggered behaviors. (d) Plasticity of the compositional rules for ISMS motor responses, and understanding plasticity of ISMS topography in different spinal cord lesion states, disease states, and following rehabilitation. All these knowledge gaps to a greater or lesser extent require novel electrode technology in order to allow high density chronic recording and stimulation. The current lack of this technology may explain why these prominent gaps in the ISMS literature currently exist. It is also argued that given the "known unknowns" in the current ISMS literature, it may be prudent to adopt and develop control schemes that can manage the current results with simple superposition and winner-take-all interactions, but can also incorporate the possible plastic and stochastic dynamic interactions that may emerge in fuller analyses over longer terms, and which have already been noted in some simpler model systems.
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Affiliation(s)
- Simon F Giszter
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Drexel University Philadelphia, PA, USA ; School of Biomedical Engineering and Health Systems, Drexel University Philadelphia, PA, USA
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Ersen A, Elkabes S, Freedman DS, Sahin M. Chronic tissue response to untethered microelectrode implants in the rat brain and spinal cord. J Neural Eng 2015; 12:016019. [PMID: 25605679 DOI: 10.1088/1741-2560/12/1/016019] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Microelectrodes implanted in the central nervous system (CNS) often fail in long term implants due to the immunological tissue response caused by tethering forces of the connecting wires. In addition to the tethering effect, there is a mechanical stress that occurs at the device-tissue interface simply because the microelectrode is a rigid body floating in soft tissue and it cannot reshape itself to comply with changes in the surrounding tissue. In the current study we evaluated the scar tissue formation to tetherless devices with two significantly different geometries in the rat brain and spinal cord in order to investigate the effects of device geometry. APPROACH One of the implant geometries resembled the wireless, floating microstimulators that we are currently developing in our laboratory and the other was a (shank only) Michigan probe for comparison. Both electrodes were implanted into either the cervical spinal cord or the motor cortices, one on each side. MAIN RESULTS The most pronounced astroglial and microglial reactions occurred within 20 μm from the device and decreased sharply at larger distances. Both cell types displayed the morphology of non-activated cells past the 100 μm perimeter. Even though the aspect ratios of the implants were different, the astroglial and microglial responses to both microelectrode types were very mild in the brain, stronger and yet limited in the spinal cord. SIGNIFICANCE These observations confirm previous reports and further suggest that tethering may be responsible for most of the tissue response in chronic implants and that the electrode size has a smaller contribution with floating electrodes. The electrode size may be playing primarily an amplifying role to the tethering forces in the brain whereas the size itself may induce chronic response in the spinal cord where the movement of surrounding tissues is more significant.
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Affiliation(s)
- Ali Ersen
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA
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Ersen A, Abdo A, Sahin M. Temperature elevation profile inside the rat brain induced by a laser beam. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:15009. [PMID: 24474503 PMCID: PMC3902302 DOI: 10.1117/1.jbo.19.1.015009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 11/14/2013] [Accepted: 12/18/2013] [Indexed: 05/22/2023]
Abstract
The thermal effect may be a desired outcome or a concerning side effect in laser-tissue interactions. Research in this area is particularly motivated by recent advances in laser applications in diagnosis and treatment of neurological disorders. Temperature as a side effect also limits the maximum power of optical transfer and harvesting of energy in implantable neural prostheses. The main objective was to investigate the thermal effect of a near-infrared laser beam directly aimed at the brain cortex. A small, custom-made thermal probe was inserted into the rat brain to make direct measurements of temperature elevations induced by a free-air circular laser beam. The time dependence and the spatial distribution of the temperature increases were studied and the maximum allowable optical power was determined to be 2.27 W/cm2 for a corresponding temperature increase of 0.5°C near the cortical surface. The results can be extrapolated for other temperature elevations, where the margin to reach potentially damaging temperatures is more relaxed, by taking advantage of linearity. It is concluded that the thermal effect depends on several factors such as the thermal properties of the neural tissue and of its surrounding structures, the optical properties of the particular neural tissue, and the laser beam size and shape. Because so many parameters play a role, the thermal effect should be investigated for each specific application separately using realistic in vivo models.
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Affiliation(s)
- Ali Ersen
- New Jersey Institute of Technology, Neural Interface Laboratory, Biomedical Engineering Department, 323 Dr. Martin Luther King, Jr. Boulevard, University Heights, Newark, New Jersey 07102-1982
| | - Ammar Abdo
- New Jersey Institute of Technology, Neural Interface Laboratory, Biomedical Engineering Department, 323 Dr. Martin Luther King, Jr. Boulevard, University Heights, Newark, New Jersey 07102-1982
| | - Mesut Sahin
- New Jersey Institute of Technology, Neural Interface Laboratory, Biomedical Engineering Department, 323 Dr. Martin Luther King, Jr. Boulevard, University Heights, Newark, New Jersey 07102-1982
- Address all correspondence to: Mesut Sahin, E-mail:
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Towe BC, Larson PJ, Gulick DW. A microwave powered injectable neural stimulator. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:5006-9. [PMID: 23367052 DOI: 10.1109/embc.2012.6347117] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
An unexpectedly simple implantable device that can achieve wireless neurostimulation consists of a short 1 cm long dipole platinum wire antenna, a Schottky diode, and a pulsed microwave transmitter. Fabricated into a 1 cm long by polyimide tubing, the implant can have a sub-millimeter diameter form factor suited to introduction into tissue by injection. Experiments that chronically implant the device next to a rat sciatic nerve show that a 915 MHz microwave transmitter emitting an average power of 0.5 watts has an ability to stimulate motor events when spaced up to 7 cm from the body surface. Tissue models consisting of saline filled tanks show the possibility of delivering milliampere pulsed current to neurosimulators though 5 centimeters or more of tissue. Such a neurostimulation system driven by microwave energy is limited in functional tissue depth by microwave SAR exposure. This report discusses some of the advantages and limitations of such a neurostimulation approach.
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Affiliation(s)
- Bruce C Towe
- Harrington Biomedical Engineering, School of Biological and Health Systems Engineering, Arizona State University, USA
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Abdo A, Ersen A, Sahin M. Near-infrared light penetration profile in the rodent brain. JOURNAL OF BIOMEDICAL OPTICS 2013; 18:075001. [PMID: 23831713 PMCID: PMC3701316 DOI: 10.1117/1.jbo.18.7.075001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Near-infrared (NIR) lasers find applications in neuro-medicine both for diagnostic and treatment purposes. Penetration depth and profile into neural tissue are critical parameters to be considered in these applications. Published data on the optical properties of rodent neural tissue are rare, despite the frequent use of rats as an animal model. The aim of this study was to measure the light intensity profile inside the rat brain using a direct method, while the medium is being illuminated by an NIR laser beam, and compare the results with in vitro measurements of transmittance in the rat brain slices. The intensity profile along the vertical axis had an exponential decline with multiple regions that could be approximated with different coefficients. The Monte Carlo method that was used to simulate light-tissue interactions and predict the scattering coefficient of brain tissue from the measurements suggested that more scattering occurred in deeper layers of the cortex. A single scattering coefficient of 125 cm-1 was estimated for cortical layers from 300 to 1500 μm and a gradually increasing value from 125 to 370 cm-1 for depths of 1500 to 3000 μm. The deviations of in vivo results from the in vitro transmittance measurements, as well as the postmortem in vivo results from the alive measurements were significant.
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Affiliation(s)
- Ammar Abdo
- New Jersey Institute of Technology, Biomedical Engineering Department, New Jersey 07102
| | - Ali Ersen
- New Jersey Institute of Technology, Biomedical Engineering Department, New Jersey 07102
| | - Mesut Sahin
- New Jersey Institute of Technology, Biomedical Engineering Department, New Jersey 07102
- Address all correspondence to: Mesut Sahin, New Jersey Institute of Technology, Biomedical Engineering Department, Newark, New Jersey 07102. Tel: 973-596-5573; Fax: 973-596-5222; E-mail:
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Abdo A, Ersen A, Sahin M. Temperature elevation inside neural tissue illuminated by NIR laser. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:3987-9. [PMID: 22255213 DOI: 10.1109/iembs.2011.6090990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Near infrared (NIR) light energy has been used in medical applications both for diagnostic and treatment purposes. Temperature elevation is the main concern in the neural tissue when illuminated with NIR light. In this report, an NIR light beam was pulsed into a rat brain cortex. The spatial maps of temperature elevation inside the neural tissue were measured directly using a micro probe. The results indicate that the temperature inside the neural tissue saturates with increasing levels of laser power.
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Affiliation(s)
- Ammar Abdo
- Biomedical Engineering Department, New Jersey Institute of Technology, Newark, NJ 07102, USA
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Abdo A, Sahin M, Freedman DS, Cevik E, Spuhler PS, Unlu MS. Floating light-activated microelectrical stimulators tested in the rat spinal cord. J Neural Eng 2011; 8:056012. [PMID: 21914931 DOI: 10.1088/1741-2560/8/5/056012] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Microelectrodes of neural stimulation utilize fine wires for electrical connections to driving electronics. Breakage of these wires and the neural tissue response due to their tethering forces are major problems encountered with long-term implantation of microelectrodes. The lifetime of an implant for neural stimulation can be substantially improved if the wire interconnects are eliminated. Thus, we proposed a floating light-activated microelectrical stimulator (FLAMES) for wireless neural stimulation. In this paradigm, a laser beam at near infrared (NIR) wavelengths will be used as a means of energy transfer to the device. In this study, microstimulators of various sizes were fabricated, with two cascaded GaAs p-i-n photodiodes, and tested in the rat spinal cord. A train of NIR pulses (0.2 ms, 50 Hz) was sent through the tissue to wirelessly activate the devices and generate the stimulus current. The forces elicited by intraspinal stimulation were measured from the ipsilateral forelimb with a force transducer. The largest forces were around 1.08 N, a significant level of force for the rat forelimb motor function. These in vivo tests suggest that the FLAMES can be used for intraspinal microstimulation even for the deepest implant locations in the rat spinal cord. The power required to generate a threshold arm movement was investigated as the laser source was moved away from the microstimulator. The results indicate that the photon density does not decrease substantially for horizontal displacements of the source that are in the same order as the beam radius. This gives confidence that the stimulation threshold may not be very sensitive to small displacement of the spinal cord relative to the spine-mounted optical power source.
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Affiliation(s)
- Ammar Abdo
- Biomedical Engineering Department, New Jersey Institute of Technology, NJ, USA
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Abstract
One of the roadblocks in the field of neural prosthetics is the lack of microelectronic devices for neural stimulation that can last a lifetime in the central nervous system. Wireless multi-electrode arrays are being developed to improve the longevity of implants by eliminating the wire interconnects as well as the chronic tissue reactions due to the tethering forces generated by these wires. An area of research that has not been sufficiently investigated is a simple single-channel passive microstimulator that can collect the stimulus energy that is transmitted wirelessly through the tissue and immediately convert it into the stimulus pulse. For example, many neural prosthetic approaches to intraspinal microstimulation require only a few channels of stimulation. Wired spinal cord implants are not practical for human subjects because of the extensive flexions and rotations that the spinal cord experiences. Thus, intraspinal microstimulation may be a pioneering application that can benefit from submillimeter-size floating stimulators. Possible means of energizing such a floating microstimulator, such as optical, acoustic, and electromagnetic waves, are discussed.
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Affiliation(s)
- Mesut Sahin
- Biomedical Engineering Department, New Jersey Institute of Technology, Newark, NJ 07102, USA.
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