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Barbruni GL, Rodino F, Ros PM, Demarchi D, Ghezzi D, Carrara S. A Wearable Real-Time System for Simultaneous Wireless Power and Data Transmission to Cortical Visual Prosthesis. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2024; 18:580-591. [PMID: 38261488 DOI: 10.1109/tbcas.2024.3357626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
Wireless, miniaturised and distributed neural interfaces are emerging neurotechnologies. Although extensive research efforts contribute to their technological advancement, the need for real-time systems enabling simultaneous wireless information and power transfer toward distributed neural implants remains crucial. Here we present a complete wearable system including a software for real-time image capturing, processing and digital data transfer; an hardware for high radiofrequency generation and modulation via amplitude shift keying; and a 3-coil inductive link adapt to operate with multiple miniaturised receivers. The system operates in real-time with a maximum frame rate of 20 Hz, reconstructing each frame with a matrix of 32 × 32 pixels. The device generates a carrier frequency of 433.92 MHz. It transmits the highest power of 32 dBm with a data rate of 6 Mbps and a variable modulation index as low as 8 %, thus potentially enabling wireless communication with 1024 miniaturised and distributed intracortical microstimulators. The system is primarily conceived as an external wearable device for distributed cortical visual prosthesis covering a visual field of 20 °. At the same time, it is modular and versatile, being suitable for multiple applications requiring simultaneous wireless information and power transfer to large-scale neural interfaces.
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Su K, Qiu Z, Xu J. A 14-Bit, 12 V-to-100 V Voltage Compliance Electrical Stimulator with Redundant Digital Calibration. MICROMACHINES 2023; 14:2001. [PMID: 38004858 PMCID: PMC10672756 DOI: 10.3390/mi14112001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/25/2023] [Accepted: 10/26/2023] [Indexed: 11/26/2023]
Abstract
Electrical stimulation is an important technique for modulating the functions of the nervous system through electrical stimulus. To implement a more competitive prototype that can tackle the domain-specific difficulties of existing electrical stimulators, three key techniques are proposed in this work. Firstly, a load-adaptive power saving technique called over-voltage detection is implemented to automatically adjust the supply voltage. Secondly, redundant digital calibration (RDC) is proposed to improve current accuracy and ensure safety during long-term electrical stimulation without costing too much circuit area and power. Thirdly, a flexible waveform generator is designed to provide arbitrary stimulus waveforms for particular applications. Measurement results show the stimulator can adjust the supply voltage from 12 V to 100 V automatically, and the measured effective resolution of the stimulation current reaches 14 bits in a full range of 6.5 mA. Without applying charge balancing techniques, the average mismatch between the cathodic and anodic current pulses in biphasic stimulus is 0.0427%. The proposed electrical stimulator can generate arbitrary stimulus waveforms, including sine, triangle, rectangle, etc., and it is supposed to be competitive for implantable and wearable devices.
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Affiliation(s)
- Kangyu Su
- College of Information and Electronics Engineering, Zhejiang University, Hangzhou 310027, China; (K.S.); (Z.Q.)
- MOE Frontier Science Center for Brain Science and Brain-Machine Integration, Zhejiang University, Hangzhou 310058, China
| | - Zhang Qiu
- College of Information and Electronics Engineering, Zhejiang University, Hangzhou 310027, China; (K.S.); (Z.Q.)
- MOE Frontier Science Center for Brain Science and Brain-Machine Integration, Zhejiang University, Hangzhou 310058, China
| | - Jian Xu
- MOE Frontier Science Center for Brain Science and Brain-Machine Integration, Zhejiang University, Hangzhou 310058, China
- Nanhu Brain-Computer Interface Institute, Hangzhou 311100, China
- Affiliated Mental Health Center & Hangzhou Seventh People’s Hospital, Zhejiang University School of Medicine, Hangzhou 310013, China
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Jeong H, Kim J, Seo JM, Neviani A. Neurostimulators for high-resolution artificial retina: ASIC design challenges and solutions. J Neural Eng 2022; 19. [PMID: 36374010 DOI: 10.1088/1741-2552/aca262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 11/14/2022] [Indexed: 11/16/2022]
Abstract
Objective.Neurostimulator is one of the most important part in artificial retina design. In this paper, we discuss the main challenges in the design of application-specific integrated circuit for high-resolution artificial retina and suggest corresponding solutions.Approach. Problems in the design of the neurostimulator for the existing artificial retina have not been solved yet are analyzed and solutions are presented. For verification of the solutions, mathematical proof, MATLAB and Ansys simulations are used.Main results. The drawbacks of resorting to a high-voltage complementary metal oxide semiconductor (CMOS) process to deal with the large voltage compliance demanded by the stimulator output stage are pointed out, and an alternative approach based on a circuit that switches the voltage of the common reference electrode is proposed to overcome. The necessity of an active discharge circuit to remove the residual charge of electrodes caused by an unbalanced stimulus is investigated. We present a circuit analysis showing that the use of a passive discharge circuit is sufficient to suppress problematic direct current in most situations. Finally, possible restrictions on input and output (I/O) count are investigated by estimating the resistive-capacitive delay caused by the interconnection between the I/O pad and the microelectrode array.Significance. The results of this paper clarified the problems currently faced by neurostimulator design for the artificial retina. Through the solutions presented in this study, circuits with more competitiveness in power and area consumption can be designed.
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Affiliation(s)
- Hyunbeen Jeong
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Jisung Kim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Jong-Mo Seo
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea.,Department of Ophthalmology, Seoul National University Hospital, Seoul, Republic of Korea
| | - Andrea Neviani
- Department of Information Engineering, University of Padova, Padova, Italy
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Sharma D, Kanaujia BK, Kaim V, Mittra R, Arya RK, Matekovits L. Design and implementation of compact dual-band conformal antenna for leadless cardiac pacemaker system. Sci Rep 2022; 12:3165. [PMID: 35210497 PMCID: PMC8873455 DOI: 10.1038/s41598-022-06904-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 02/01/2022] [Indexed: 11/09/2022] Open
Abstract
The leadless cardiac pacemaker is a pioneering device for heart patients. Its rising success requires the design of compact implantable antennas. In this paper, we describe a circularly polarized Hilbert curve inspired loop antenna. The proposed antenna works in the WMTS (Wireless Medical Telemetry Services) 1.4 GHz and ISM (Industrial, Scientific, and Medical) 2.45 GHz bands. High dielectric constant material Rogers RT/Duroid 6010 LM ([Formula: see text]=10) and fractal geometry helps to design the antenna with a small footprint of 9.1 mm3 (6 mm × 6 mm × 0.254 mm). The designed antenna has a conformal shape that fits inside a leadless pacemaker's capsule is surrounded by IC models and battery, which are tightly packed in the device enclosure. Subsequently, the integrated prototype is simulated deep inside at the center of the multi-layer canonical heart model. To verify experimentally, we have put dummy electronics (IC and battery) inside the 3D printed pacemaker's capsule and surfaced the fabricated conformal antenna around the inner curved body of the TCP (Transcatheter Pacing) capsule. Furthermore, we have tested the TCP capsule by inserting it in a ballistic gel phantom and minced pork. The measured impedance bandwidths at 1.4 GHz and 2.45 GHz are 250 MHz and 430 MHz, whereas measured gains are - 33.2 dBi, and - 28.5 dBi, respectively.
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Affiliation(s)
- Deepti Sharma
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Binod Kumar Kanaujia
- Dr. B R Ambedkar National Institute of Technology, Jalandhar (Punjab), 144011, India
| | - Vikrant Kaim
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Raj Mittra
- University of Central Florida, Orlando, FL, 32816, USA.,Electrical and Computer Engineering Department, Faculty of Engineering, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
| | - Ravi Kumar Arya
- National Institute of Technology Delhi, New Delhi, 110040, India
| | - Ladislau Matekovits
- Department of Electronics and Telecommunications, Politecnico Di Torino, Turin, Italy. .,Department of Measurements and Optical Electronics, Politehnica University Timisoara, 300006, Timisoara, Romania. .,Istituto di Elettronica e di Ingegneria dell'Informazione e delle Telecomunicazioni, National Research Council, 10129, Turin, Italy.
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Choi DH, Roh H, Im M, Jee DW. A 4.49nW/Pixel Light-to-Stimulus Duration Converter-Based Retinal Prosthesis Chip. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2021; 15:1140-1148. [PMID: 34784285 DOI: 10.1109/tbcas.2021.3128418] [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
This paper presents a 288-pixel retinal prosthesis (RP) chip implemented in a 0.18 μm CMOS process. The proposed light-to-stimulus duration converter (LSDC) and biphasic stimulator generate a wide range of retinal stimuli proportional to the incident light intensity at a low supply voltage of 1V. The implemented chip shows 25.5 dB dynamic stimulation range and the state-of-the art low power consumption of 4.49 nW/pixel. Ex-vivo experiments were performed with a mouse retina and patch-clamp recording. The electrical artifact recorded by the patch electrode demonstrates that the proposed chip can generate electrical stimuli that have different pulse durations depending on the light intensity. Correspondingly, the spike counts in a retinal ganglion cell (RGC) were successfully modulated by the brightness of the light stimuli.
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Culaclii S, Wang PM, Taccola G, Yang W, Bailey B, Chen YP, Lo YK, Liu W. A Biomimetic, SoC-Based Neural Stimulator for Novel Arbitrary-Waveform Stimulation Protocols. Front Neurosci 2021; 15:697731. [PMID: 34393710 PMCID: PMC8358079 DOI: 10.3389/fnins.2021.697731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 07/07/2021] [Indexed: 11/15/2022] Open
Abstract
Novel neural stimulation protocols mimicking biological signals and patterns have demonstrated significant advantages as compared to traditional protocols based on uniform periodic square pulses. At the same time, the treatments for neural disorders which employ such protocols require the stimulator to be integrated into miniaturized wearable devices or implantable neural prostheses. Unfortunately, most miniaturized stimulator designs show none or very limited ability to deliver biomimetic protocols due to the architecture of their control logic, which generates the waveform. Most such designs are integrated into a single System-on-Chip (SoC) for the size reduction and the option to implement them as neural implants. But their on-chip stimulation controllers are fixed and limited in memory and computing power, preventing them from accommodating the amplitude and timing variances, and the waveform data parameters necessary to output biomimetic stimulation. To that end, a new stimulator architecture is proposed, which distributes the control logic over three component tiers - software, microcontroller firmware and digital circuits of the SoC, which is compatible with existing and future biomimetic protocols and with integration into implantable neural prosthetics. A portable prototype with the proposed architecture is designed and demonstrated in a bench-top test with various known biomimetic output waveforms. The prototype is also tested in vivo to deliver a complex, continuous biomimetic stimulation to a rat model of a spinal-cord injury. By delivering this unique biomimetic stimulation, the device is shown to successfully reestablish the connectivity of the spinal cord post-injury and thus restore motor outputs in the rat model.
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Affiliation(s)
- Stanislav Culaclii
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
| | - Po-Min Wang
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
| | - Giuliano Taccola
- Neuroscience Department, International School for Advanced Studies, Trieste, Italy
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, United States
| | - William Yang
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
| | - Brett Bailey
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
| | - Yan-Peng Chen
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, CA, United States
| | - Yi-Kai Lo
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
- Niche Biomedical Inc., Los Angeles, CA, United States
| | - Wentai Liu
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, CA, United States
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, United States
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, United States
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Engur Y, Yigit HA, Kulah H. 13.56 MHz Triple Mode Rectifier Circuit With Extended Coupling Range for Wirelessly Powered Implantable Medical Devices. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2021; 15:68-79. [PMID: 33360999 DOI: 10.1109/tbcas.2020.3047551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
In this work, a wide input/output range triple mode rectifier circuit operating at 13.56 MHz is implemented to power up medical implants. The proposed novel multi-mode rectifier circuit charges the load for an extended coupling range and eliminates the requirement of alignment magnets. The charging process is achieved in three different modes based on the voltage level of the received signal affected by the distance and the alignment of the inductively coupled coils. Current mode (CM) circuit is activated for loosely coupled coils whereas voltage mode (VM) rectification is proposed for high coupling ratios. Extended coupling range is covered with the activation of half wave rectification mode (HWM) in between CM and VM. The rectifier circuit utilizes these three modes in a single circuit operating at 13.56 MHz according to the receiver signal voltage. The circuit is implemented in TSMC 180 nm BCD technology with 0.9 mm2 active area and tested with printed coils. According to the measurements, the circuit operates in the received power range of 4 to 57.7 mW, which corresponds to 0.10-0.42 coupling range. The maximum power conversion efficiency (PCE) of each operation mode is 51.78%, 82.49%, and 89.34% for CM, HWM, and VM, respectively, while charging a 3.3 V load.
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Park JH, Tan JSY, Wu H, Dong Y, Yoo J. 1225-Channel Neuromorphic Retinal-Prosthesis SoC With Localized Temperature-Regulation. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2020; 14:1230-1240. [PMID: 33156793 DOI: 10.1109/tbcas.2020.3036091] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A 1225-Channel Neuromorphic Retinal Prosthesis (RP) SoC is presented. Existing RP SoCs directly convert light intensity to electrical stimulus, which limit the adoption of delicate stimulus patterns to increase visual acuity. Moreover, a conventional centralized image processor leads to the local hot spot that poses a risk to the nearby retinal cells. To solve these issues, the proposed SoC adopts a distributed Neuromorphic Image Processor (NMIP) located within each pixel that extracts the outline of the incoming image, which reduces current dispersion and stimulus power compared with light-intensity proportional stimulus pattern. A spike-based asynchronous digital operation results in the power consumption of 56.3 nW/Ch without local temperature hot spot. At every 5×5 pixels, the localized (49-point) temperature-regulation circuit limits the temperature increase of neighboring retinal cells to less than 1 °C, and the overall power consumption of the SoC to be less than that of the human eye. The 1225-channel SoC fabricated in 0.18 μm 1P6M CMOS occupies 15mm2 while consuming 2.7 mW, and is successfully verified with image reconstruction demonstration.
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Yen TY, Ker MD. Design of Dual-Mode Stimulus Chip With Built-In High Voltage Generator for Biomedical Applications. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2020; 14:961-970. [PMID: 32746341 DOI: 10.1109/tbcas.2020.2999398] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this work, a dual-mode stimulus chip with a built-in high voltage generator was proposed to offer a broad-range current or voltage stimulus patterns for biomedical applications. With an on-chip and built-in high voltage generator, this stimulus chip could generate the required high voltage supply without additional supply voltage. With a nearly 20 V operating voltage, the overstress and reliability issues of the stimulus circuits were thoroughly considered and carefully addressed in this work. This stimulus system only requires an area of 0.22 mm2 per single channel and is fully on-chip implemented without any additional external components. The dual-mode stimulus chip was fabricated in a 0.25-μm 2.5V/5V/12V CMOS (complementary metal-oxide-semiconductor) process, which can generate the biphasic current or voltage stimulus pulses. The current level of stimulus is up to 5 mA, and the voltage level of stimulus can be up to 10 V. Moreover, this chip has been successfully applied to stimulate a guinea pig in an animal experiment. The proposed dual-mode stimulus system has been verified in electrical tests and also demonstrated its stimulation function in animal experiments.
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Kuo PH, Wong OY, Tzeng CK, Wu PW, Chiao CC, Chen PH, Chen PC, Tsai YC, Chu FL, Ohta J, Tokuda T, Noda T, Wu CY. Improved Charge Pump Design and Ex Vivo Experimental Validation of CMOS 256-Pixel Photovoltaic-Powered Subretinal Prosthetic Chip. IEEE Trans Biomed Eng 2019; 67:1490-1504. [PMID: 31494538 DOI: 10.1109/tbme.2019.2938807] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
An improved design of CMOS 256-pixel photovoltaic-powered implantable chip for subretinal prostheses is presented. In the proposed subretinal chip, a high-efficiency fully-integrated 4× charge pump is designed and integrated with on-chip photovoltaic (PV) cells and a 256-pixel array with active pixel sensors (APS) for image light sensing, biphasic constant current stimulators, and electrodes. Thus the PV voltage generated by infrared (IR) light can be boosted to above 1V so that the charge injection is increased. The proposed chip adopts the 32-phase divisional power supply scheme (DPSS) to reduce the required supply current and thus the required area of the PV cells. The proposed chip is designed and fabricated in 180-nm CMOS image sensor (CIS) technology and post-processed with biocompatible IrOx electrodes and silicone packaging. From the electrical measurement results, the measured stimulation frequency is 28.3 Hz under the equivalent electrode impedance load. The measured maximum output stimulation current is 7.1 μA and the amount of injected charges per pixel is 7.36 nC under image light intensity of 3200 lux and IR light intensity of 100 mW/cm2. The function of the proposed chip has been further validated successfully with the ex vivo experimental results by recording the electrophysiological responses of retinal ganglion cells (RGCs) of retinas from retinal degeneration (rd1) mice with a multi-electrode array (MEA). The measured average threshold injected charge is about 3.97 nC which is consistent with that obtained from the patch clamp recording on retinas from wild type (C57BL/6) mice with a single electrode pair.
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Qiang Y, Artoni P, Seo KJ, Culaclii S, Hogan V, Zhao X, Zhong Y, Han X, Wang PM, Lo YK, Li Y, Patel HA, Huang Y, Sambangi A, Chu JSV, Liu W, Fagiolini M, Fang H. Transparent arrays of bilayer-nanomesh microelectrodes for simultaneous electrophysiology and two-photon imaging in the brain. SCIENCE ADVANCES 2018; 4:eaat0626. [PMID: 30191176 PMCID: PMC6124910 DOI: 10.1126/sciadv.aat0626] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 07/24/2018] [Indexed: 05/06/2023]
Abstract
Transparent microelectrode arrays have emerged as increasingly important tools for neuroscience by allowing simultaneous coupling of big and time-resolved electrophysiology data with optically measured, spatially and type resolved single neuron activity. Scaling down transparent electrodes to the length scale of a single neuron is challenging since conventional transparent conductors are limited by their capacitive electrode/electrolyte interface. In this study, we establish transparent microelectrode arrays with high performance, great biocompatibility, and comprehensive in vivo validations from a recently developed, bilayer-nanomesh material composite, where a metal layer and a low-impedance faradaic interfacial layer are stacked reliably together in a same transparent nanomesh pattern. Specifically, flexible arrays from 32 bilayer-nanomesh microelectrodes demonstrated near-unity yield with high uniformity, excellent biocompatibility, and great compatibility with state-of-the-art wireless recording and real-time artifact rejection system. The electrodes are highly scalable, with 130 kilohms at 1 kHz at 20 μm in diameter, comparable to the performance of microelectrodes in nontransparent Michigan arrays. The highly transparent, bilayer-nanomesh microelectrode arrays allowed in vivo two-photon imaging of single neurons in layer 2/3 of the visual cortex of awake mice, along with high-fidelity, simultaneous electrical recordings of visual-evoked activity, both in the multi-unit activity band and at lower frequencies by measuring the visual-evoked potential in the time domain. Together, these advances reveal the great potential of transparent arrays from bilayer-nanomesh microelectrodes for a broad range of utility in neuroscience and medical practices.
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Affiliation(s)
- Yi Qiang
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Pietro Artoni
- Center for Life Science, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Kyung Jin Seo
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Stanislav Culaclii
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Victoria Hogan
- Center for Life Science, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Xuanyi Zhao
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Yiding Zhong
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Xun Han
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Po-Min Wang
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yi-Kai Lo
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yueming Li
- School of Material Science and Engineering, Tsinghua University, Beijing 100084, China
| | - Henil A. Patel
- Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Yifu Huang
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Abhijeet Sambangi
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Jung Soo V. Chu
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
| | - Wentai Liu
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Department of Electrical and Computer Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Michela Fagiolini
- Center for Life Science, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Hui Fang
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115, USA
- Department of Bioengineering, Northeastern University, Boston, MA 02120, USA
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Culaclii S, Kim B, Lo YK, Li L, Liu W. Online Artifact Cancelation in Same-Electrode Neural Stimulation and Recording Using a Combined Hardware and Software Architecture. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2018; 12:601-613. [PMID: 29877823 PMCID: PMC6299268 DOI: 10.1109/tbcas.2018.2816464] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Advancing studies of neural network dynamics and developments of closed-loop neural interfaces requires the ability to simultaneously stimulate and record the neural cells. Recording adjacent to or at the stimulation site produces artifact signals that are orders of magnitude larger than the neural responses of interest. These signals often saturate the recording amplifier causing distortion or loss of short-latency evoked responses. This paper proposes a method to cancel the artifact in simultaneous neural recording and stimulation on the same electrode. By combining a novel hardware architecture with concurrent software processing, the design achieves neural signal recovery in a wide range of conditions. The proposed system uniquely demonstrates same-electrode stimulation and recording, with neural signal recovery in presence of stimulation artifact 100 dB larger in magnitude than the underlying signals. The system is tested both in vitro and in vivo, during concurrent stimulation and recording on the same electrode. In vivo results in a rodent model are compared to recordings made by a commercial neural amplifier system connected in parallel.
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Lo YK, Wang PM, Dubrovsky G, Wu MD, Chan M, Dunn JCY, Liu W. A Wireless Implant for Gastrointestinal Motility Disorders. MICROMACHINES 2018; 9:E17. [PMID: 30393295 PMCID: PMC6187657 DOI: 10.3390/mi9010017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 12/21/2017] [Accepted: 12/27/2017] [Indexed: 02/06/2023]
Abstract
Implantable functional electrical stimulation (IFES) has demonstrated its effectiveness as an alternative treatment option for diseases incurable pharmaceutically (e.g., retinal prosthesis, cochlear implant, spinal cord implant for pain relief). However, the development of IFES for gastrointestinal (GI) tract modulation is still limited due to the poorly understood GI neural network (gut⁻brain axis) and the fundamental difference among activating/monitoring smooth muscles, skeletal muscles and neurons. This inevitably imposes different design specifications for GI implants. This paper thus addresses the design requirements for an implant to treat GI dysmotility and presents a miniaturized wireless implant capable of modulating and recording GI motility. This implant incorporates a custom-made system-on-a-chip (SoC) and a heterogeneous system-in-a-package (SiP) for device miniaturization and integration. An in vivo experiment using both rodent and porcine models is further conducted to validate the effectiveness of the implant.
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Affiliation(s)
- Yi-Kai Lo
- Niche Biomedical, LLC, Los Angeles, CA 90095, USA.
| | - Po-Min Wang
- Department of Bioengineering, University of California, Los Angeles, CA 90095, USA.
| | - Genia Dubrovsky
- Department of Surgery, University of California, Los Angeles, CA 90095, USA.
| | - Ming-Dao Wu
- Department of Bioengineering, University of California, Los Angeles, CA 90095, USA.
| | - Michael Chan
- Department of Bioengineering, University of California, Los Angeles, CA 90095, USA.
| | - James C Y Dunn
- Department of Bioengineering, University of California, Los Angeles, CA 90095, USA.
- Department of Surgery, University of California, Los Angeles, CA 90095, USA.
- Department of Surgery, Stanford University, Stanford, CA 94305, USA.
| | - Wentai Liu
- Department of Bioengineering, University of California, Los Angeles, CA 90095, USA.
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Lo YK, Kuan YC, Culaclii S, Kim B, Wang PM, Chang CW, Massachi JA, Zhu M, Chen K, Gad P, Edgerton VR, Liu W. A Fully Integrated Wireless SoC for Motor Function Recovery After Spinal Cord Injury. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2017; 11:497-509. [PMID: 28489550 PMCID: PMC5562024 DOI: 10.1109/tbcas.2017.2679441] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This paper presents a wirelessly powered, fully integrated system-on-a-chip (SoC) supporting 160-channel stimulation, 16-channel recording, and 48-channel bio-impedance characterization to enable partial motor function recovery through epidural spinal cord electrical stimulation. A wireless transceiver is designed to support quasi full-duplex data telemetry at a data rate of 2 Mb/s. Furthermore, a unique in situ bio-impedance characterization scheme based on time-domain analysis is implemented to derive the Randles cell electrode model of the electrode-electrolyte interface. The SoC supports concurrent stimulation and recording while the high-density stimulator array meets an output compliance voltage of up to ±10 V with versatile stimulus programmability. The SoC consumes 18 mW and occupies a chip area of 5.7 mm × 4.4 mm using 0.18 μm high-voltage CMOS process. In our in vivo rodent experiment, the SoC is used to perform wireless recording of EMG responses while stimulation is applied to enable the standing and stepping of a paralyzed rat. To facilitate the system integration, a novel thin film polymer packaging technique is developed to provide a heterogeneous integration of the SoC, coils, discrete components, and high-density flexible electrode array, resulting in a miniaturized prototype implant with a weight and form factor of 0.7 g and 0.5 cm3, respectively.
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Liu W, Wang PM, Lo YK. Towards Closed-Loop Neuromodulation: A Wireless Miniaturized Neural Implant SoC. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2017; 10194. [PMID: 30410205 DOI: 10.1117/12.2263566] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
This work reports a platform technology toward the development of closed-loop neuromodulation. A neural implant based on the SoC developed in our laboratory is used as an example to illustrate the necessary functionalities for the efficacious implantable system. We also present an example of using the system to investigate the epidural stimulation for partial motor function recovery after spinal cord injury in a rat model. This hardware-software co-design tool demonstrate its promising potential towards an effective closed-loop neuromodulation for various biomedical applications.
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Affiliation(s)
- Wentai Liu
- University of California, Los Angeles, Los Angeles, CA, USA 90095
| | - Po-Min Wang
- University of California, Los Angeles, Los Angeles, CA, USA 90095
| | - Yi-Kai Lo
- University of California, Los Angeles, Los Angeles, CA, USA 90095
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Lo YK, Chang CW, Liu W. Bio-impedance characterization technique with implantable neural stimulator using biphasic current stimulus. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2014:474-7. [PMID: 25569999 DOI: 10.1109/embc.2014.6943631] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Knowledge of the bio-impedance and its equivalent circuit model at the electrode-electrolyte/tissue interface is important in the application of functional electrical stimulation. Impedance can be used as a merit to evaluate the proximity between electrodes and targeted tissues. Understanding the equivalent circuit parameters of the electrode can further be leveraged to set a safe boundary for stimulus parameters in order not to exceed the water window of electrodes. In this paper, we present an impedance characterization technique and implement a proof-of-concept system using an implantable neural stimulator and an off-the-shelf microcontroller. The proposed technique yields the parameters of the equivalent circuit of an electrode through large signal analysis by injecting a single low-intensity biphasic current stimulus with deliberately inserted inter-pulse delay and by acquiring the transient electrode voltage at three well-specified timings. Using low-intensity stimulus allows the derivation of electrode double layer capacitance since capacitive charge-injection dominates when electrode overpotential is small. Insertion of the inter-pulse delay creates a controlled discharge time to estimate the Faradic resistance. The proposed method has been validated by measuring the impedance of a) an emulated Randles cells made of discrete circuit components and b) a custom-made platinum electrode array in-vitro, and comparing estimated parameters with the results derived from an impedance analyzer. The proposed technique can be integrated into implantable or commercial neural stimulator system at low extra power consumption, low extra-hardware cost, and light computation.
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17
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Maghami MH, Sodagar AM, Sawan M. Versatile Stimulation Back-End With Programmable Exponential Current Pulse Shapes for a Retinal Visual Prosthesis. IEEE Trans Neural Syst Rehabil Eng 2016; 24:1243-1253. [PMID: 27046904 DOI: 10.1109/tnsre.2016.2542112] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper reports on the design, implementation, and test of a stimulation back-end, for an implantable retinal prosthesis. In addition to traditional rectangular pulse shapes, the circuit features biphasic stimulation pulses with both rising and falling exponential shapes, whose time constants are digitally programmable. A class-B second generation current conveyor is used as a wide-swing, high-output-resistance stimulation current driver, delivering stimulation current pulses of up to ±96 μA to the target tissue. Duration of the generated current pulses is programmable within the range of 100 μs to 3 ms. Current-mode digital-to-analog converters (DACs) are used to program the amplitudes of the stimulation pulses. Fabricated using the IBM 130 nm process, the circuit consumes 1.5×1.5 mm2 of silicon area. According to the measurements, the DACs exhibit DNL and INL of 0.23 LSB and 0.364 LSB, respectively. Experimental results indicate that the stimuli generator meets expected requirements when connected to electrode-tissue impedance of as high as 25 k Ω. Maximum power consumption of the proposed design is 3.4 mW when delivering biphasic rectangular pulses to the target load. A charge pump block is in charge of the upconversion of the standard 1.2-V supply voltage to ±3.3V.
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Lin YP, Tang KT. An Inductive Power and Data Telemetry Subsystem With Fast Transient Low Dropout Regulator for Biomedical Implants. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2016; 10:435-444. [PMID: 26285218 DOI: 10.1109/tbcas.2015.2447526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This paper presents a capacitorless low-dropout (LDO) regulator with fast transient response and data reverse telemetry circuit for fully implantable wireless transmission applications. We propose a novel hybrid feedback structure using high-frequency compensation technology to achieve a rapid transient response for the LDO regulator. To reduce the size of the implant and transmit neural recordings through the same coil without interfering with power transmission, the load-shift-key (LSK) modulation technique is adopted for back data telemetry. The proposed implantable chip, fabricated using commercial 0.18 μm complementary metal oxide semiconductor technology, yielded an output power of 15 mW. Under 1.15 V operation voltage, the maximum overshoot and undershoot voltages were less than 45 mV and 55 mV, respectively, for a 15 mA full-load current whose rising and falling time were less than 100 ns. The proposed LSK transceiver uses a digitized demodulator to improve bandwidth efficiency for low carrier frequency operation.
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Lo YK, Chang CW, Kuan YC, Culaclii S, Kim B, Chen K, Gad P, Edgerton VR, Liu W. A 176-Channel 0.5cm 3 0.7g Wireless Implant for Motor Function Recovery after Spinal Cord Injury. DIGEST OF TECHNICAL PAPERS. IEEE INTERNATIONAL SOLID-STATE CIRCUITS CONFERENCE 2016; 2016:382-383. [PMID: 27672236 PMCID: PMC5035117 DOI: 10.1109/isscc.2016.7418067] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
Affiliation(s)
- Yi-Kai Lo
- University of California, Los Angeles, CA
| | | | | | | | - Brian Kim
- University of California, Los Angeles, CA
| | | | - Parag Gad
- University of California, Los Angeles, CA
| | | | - Wentai Liu
- University of California, Los Angeles, CA
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Boinagrov D, Lei X, Goetz G, Kamins TI, Mathieson K, Galambos L, Harris JS, Palanker D. Photovoltaic Pixels for Neural Stimulation: Circuit Models and Performance. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2016; 10:85-97. [PMID: 25622325 PMCID: PMC6497060 DOI: 10.1109/tbcas.2014.2376528] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Photovoltaic conversion of pulsed light into pulsed electric current enables optically-activated neural stimulation with miniature wireless implants. In photovoltaic retinal prostheses, patterns of near-infrared light projected from video goggles onto subretinal arrays of photovoltaic pixels are converted into patterns of current to stimulate the inner retinal neurons. We describe a model of these devices and evaluate the performance of photovoltaic circuits, including the electrode-electrolyte interface. Characteristics of the electrodes measured in saline with various voltages, pulse durations, and polarities were modeled as voltage-dependent capacitances and Faradaic resistances. The resulting mathematical model of the circuit yielded dynamics of the electric current generated by the photovoltaic pixels illuminated by pulsed light. Voltages measured in saline with a pipette electrode above the pixel closely matched results of the model. Using the circuit model, our pixel design was optimized for maximum charge injection under various lighting conditions and for different stimulation thresholds. To speed discharge of the electrodes between the pulses of light, a shunt resistor was introduced and optimized for high frequency stimulation.
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Lo YK, Chen K, Gad P, Liu W. An On-Chip Multi-Voltage Power Converter With Leakage Current Prevention Using 0.18 μm High-Voltage CMOS Process. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2016; 10:163-174. [PMID: 25616076 DOI: 10.1109/tbcas.2014.2371695] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In this paper, we present an on-chip multi-voltage power converter incorporating of a quad-voltage timing-control rectifier and regulators to produce ±12 V and ±1.8 V simultaneously through inductive powering. The power converter achieves a PCE of 77.3% with the delivery of more than 100 mW to the implant. The proposed rectifier adopts a two-phase start-up scheme and mixed-voltage gate controller to avoid substrate leakage current. This current cannot be prevented by the conventional dynamic substrate biasing technique when using the high-voltage CMOS process with transistor threshold voltage higher than the turn-on voltage of parasitic diodes. High power conversion efficiency is achieved by 1) substrate leakage current prevention, 2) operating all rectifying transistors as switches with boosted gate control voltages, and 3) compensating the delayed turn-on and preventing reverse leakage current of rectifying switches with the proposed look-ahead comparator. This chip occupies an area of 970 μm × 4500 μm in a 0.18 μ m 32 V HV CMOS process. The quad-voltage timing-control rectifier alone is able to output a high DC voltage at the range of [2.5 V, 25 V]. With this power converter, both bench-top experiment and in-vivo power link test using a rat model were validated.
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Lee B, Kiani M, Ghovanloo M. A Triple-Loop Inductive Power Transmission System for Biomedical Applications. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2016; 10:138-48. [PMID: 25667358 DOI: 10.1109/tbcas.2014.2376965] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A triple-loop wireless power transmission (WPT) system equipped with closed-loop global power control, adaptive transmitter (Tx) resonance compensation (TRC), and automatic receiver (Rx) resonance tuning (ART) is presented. This system not only opposes coupling and load variations but also compensates for changes in the environment surrounding the inductive link to enhance power transfer efficiency (PTE) in applications such as implantable medical devices (IMDs). The Tx was built around a commercial off-the-shelf (COTS) radio-frequency identification (RFID) reader, operating at 13.56 MHz. A local Tx loop finds the optimal capacitance in parallel with the Tx coil by adjusting a varactor. A global power control loop maintains the received power at a desired level in the presence of changes in coupling distance, coil misalignments, and loading. Moreover, a local Rx loop is implemented inside a power management integrated circuit (PMIC) to avoid PTE degradation due to the Rx coil surrounding environment and process variations. The PMIC was fabricated in a 0.35- μm 4M2P standard CMOS process with 2.54 mm(2) active area. Measurement results show that the proposed triple-loop system improves the overall PTE by up to 10.5% and 4.7% compared to a similar open- and single closed-loop system, respectively, at nominal coil distance of 2 cm. The added TRC and ART loops contribute 2.3% and 1.4% to the overall PTE of 13.5%, respectively. This is the first WPT system to include three loops to dynamically compensate for environment and circuit variations and improve the overall power efficiency all the way from the driver output in Tx to the load in Rx.
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van Dongen MN, Serdijn WA. A Power-Efficient Multichannel Neural Stimulator Using High-Frequency Pulsed Excitation From an Unfiltered Dynamic Supply. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2016; 10:61-71. [PMID: 25438324 DOI: 10.1109/tbcas.2014.2363736] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This paper presents a neural stimulator system that employs a fundamentally different way of stimulating neural tissue compared to classical constant current stimulation. A stimulation pulse is composed of a sequence of current pulses injected at a frequency of 1 MHz for which the duty cycle is used to control the stimulation intensity. The system features 8 independent channels that connect to any of the 16 electrodes at the output. A sophisticated control system allows for individual control of each channel's stimulation and timing parameters. This flexibility makes the system suitable for complex electrode configurations and current steering applications. Simultaneous multichannel stimulation is implemented using a high frequency alternating technique, which reduces the amount of electrode switches by a factor 8. The system has the advantage of requiring a single inductor as its only external component. Furthermore it offers a high power efficiency, which is nearly independent on both the voltage over the load as well as on the number of simultaneously operated channels. Measurements confirm this: in multichannel mode the power efficiency can be increased for specific cases to 40% compared to 20% that is achieved by state-of-the-art classical constant current stimulators with adaptive power supply.
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Implantable neurotechnologies: electrical stimulation and applications. Med Biol Eng Comput 2016; 54:63-76. [PMID: 26753775 DOI: 10.1007/s11517-015-1442-0] [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: 08/13/2015] [Accepted: 12/14/2015] [Indexed: 12/23/2022]
Abstract
Neural stimulation using injected electrical charge is widely used both in functional therapies and as an experimental tool for neuroscience applications. Electrical pulses can induce excitation of targeted neural pathways that aid in the treatment of neural disorders or dysfunction of the central and peripheral nervous system. In this review, we summarize the recent trends in the field of electrical stimulation for therapeutic interventions of nervous system disorders, such as for the restoration of brain, eye, ear, spinal cord, nerve and muscle function. Neural prosthetic applications are discussed, and functional electrical stimulation parameters for treating such disorders are reviewed. Important considerations for implantable packaging and enhancing device reliability are also discussed. Neural stimulators are expected to play a profound role in implantable neural devices that treat disorders and help restore functions in injured or disabled nervous system.
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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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Lewis PM, Ackland HM, Lowery AJ, Rosenfeld JV. Restoration of vision in blind individuals using bionic devices: a review with a focus on cortical visual prostheses. Brain Res 2014; 1595:51-73. [PMID: 25446438 DOI: 10.1016/j.brainres.2014.11.020] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 11/05/2014] [Accepted: 11/08/2014] [Indexed: 12/13/2022]
Abstract
The field of neurobionics offers hope to patients with sensory and motor impairment. Blindness is a common cause of major sensory loss, with an estimated 39 million people worldwide suffering from total blindness in 2010. Potential treatment options include bionic devices employing electrical stimulation of the visual pathways. Retinal stimulation can restore limited visual perception to patients with retinitis pigmentosa, however loss of retinal ganglion cells precludes this approach. The optic nerve, lateral geniculate nucleus and visual cortex provide alternative stimulation targets, with several research groups actively pursuing a cortically-based device capable of driving several hundred stimulating electrodes. While great progress has been made since the earliest works of Brindley and Dobelle in the 1960s and 1970s, significant clinical, surgical, psychophysical, neurophysiological, and engineering challenges remain to be overcome before a commercially-available cortical implant will be realized. Selection of candidate implant recipients will require assessment of their general, psychological and mental health, and likely responses to visual cortex stimulation. Implant functionality, longevity and safety may be enhanced by careful electrode insertion, optimization of electrical stimulation parameters and modification of immune responses to minimize or prevent the host response to the implanted electrodes. Psychophysical assessment will include mapping the positions of potentially several hundred phosphenes, which may require repetition if electrode performance deteriorates over time. Therefore, techniques for rapid psychophysical assessment are required, as are methods for objectively assessing the quality of life improvements obtained from the implant. These measures must take into account individual differences in image processing, phosphene distribution and rehabilitation programs that may be required to optimize implant functionality. In this review, we detail these and other challenges facing developers of cortical visual prostheses in addition to briefly outlining the epidemiology of blindness, and the history of cortical electrical stimulation in the context of visual prosthetics.
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Affiliation(s)
- Philip M Lewis
- Department of Neurosurgery, Alfred Hospital, Melbourne, Australia; Department of Surgery, Monash University, Central Clinical School, Melbourne, Australia; Monash Vision Group, Faculty of Engineering, Monash University, Melbourne, Australia; Monash Institute of Medical Engineering, Monash University, Melbourne, Australia.
| | - Helen M Ackland
- Department of Neurosurgery, Alfred Hospital, Melbourne, Australia; Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
| | - Arthur J Lowery
- Monash Vision Group, Faculty of Engineering, Monash University, Melbourne, Australia; Monash Institute of Medical Engineering, Monash University, Melbourne, Australia; Department of Electrical and Computer Systems Engineering, Faculty of Engineering, Monash University, Melbourne, Australia.
| | - Jeffrey V Rosenfeld
- Department of Neurosurgery, Alfred Hospital, Melbourne, Australia; Department of Surgery, Monash University, Central Clinical School, Melbourne, Australia; Monash Vision Group, Faculty of Engineering, Monash University, Melbourne, Australia; Monash Institute of Medical Engineering, Monash University, Melbourne, Australia; F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, USA.
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Bai S, Skafidas S. On the analysis of using 3-coil wireless power transfer system in retinal prosthesis. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2014; 2014:6104-6107. [PMID: 25571390 DOI: 10.1109/embc.2014.6945022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Designing a wireless power transmission system(WPTS) using inductive coupling has been investigated extensively in the last decade. Depending on the different configurations of the coupling system, there have been various designing methods to optimise the power transmission efficiency based on the tuning circuitry, quality factor optimisation and geometrical configuration. Recently, a 3-coil WPTS was introduced in retinal prosthesis to overcome the low power transferring efficiency due to low coupling coefficient. Here we present a method to analyse this 3-coil WPTS using the S-parameters to directly obtain maximum achievable power transferring efficiency. Through electromagnetic simulation, we brought a question on the condition of improvement using 3-coil WPTS in powering retinal prosthesis.
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