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Chung WG, Jang J, Cui G, Lee S, Jeong H, Kang H, Seo H, Kim S, Kim E, Lee J, Lee SG, Byeon SH, Park JU. Liquid-metal-based three-dimensional microelectrode arrays integrated with implantable ultrathin retinal prosthesis for vision restoration. NATURE NANOTECHNOLOGY 2024; 19:688-697. [PMID: 38225357 PMCID: PMC11106006 DOI: 10.1038/s41565-023-01587-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Accepted: 11/28/2023] [Indexed: 01/17/2024]
Abstract
Electronic retinal prostheses for stimulating retinal neurons are promising for vision restoration. However, the rigid electrodes of conventional retinal implants can inflict damage on the soft retina tissue. They also have limited selectivity due to their poor proximity to target cells in the degenerative retina. Here we present a soft artificial retina (thickness, 10 μm) where flexible ultrathin photosensitive transistors are integrated with three-dimensional stimulation electrodes of eutectic gallium-indium alloy. Platinum nanoclusters locally coated only on the tip of these three-dimensional liquid-metal electrodes show advantages in reducing the impedance of the stimulation electrodes. These microelectrodes can enhance the proximity to the target retinal ganglion cells and provide effective charge injections (72.84 mC cm-2) to elicit neural responses in the retina. Their low Young's modulus (234 kPa), owing to their liquid form, can minimize damage to the retina. Furthermore, we used an unsupervised machine learning approach to effectively identify the evoked spikes to grade neural activities within the retinal ganglion cells. Results from in vivo experiments on a retinal degeneration mouse model reveal that the spatiotemporal distribution of neural responses on their retina can be mapped under selective localized illumination areas of light, suggesting the restoration of their vision.
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Affiliation(s)
- Won Gi Chung
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Jiuk Jang
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Gang Cui
- Institute of Vision Research, Department of Ophthalmology, Severance Eye Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Sanghoon Lee
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Han Jeong
- Institute of Vision Research, Department of Ophthalmology, Severance Eye Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Haisu Kang
- School of Chemical Engineering, Pusan National University, Busan, Republic of Korea
| | - Hunkyu Seo
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Sumin Kim
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Enji Kim
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Junwon Lee
- Institute of Vision Research, Department of Ophthalmology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Seung Geol Lee
- School of Chemical Engineering, Pusan National University, Busan, Republic of Korea.
- Department of Organic Material Science and Engineering, Pusan National University, Busan, Republic of Korea.
| | - Suk Ho Byeon
- Institute of Vision Research, Department of Ophthalmology, Severance Eye Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea.
| | - Jang-Ung Park
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea.
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea.
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea.
- Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Republic of Korea.
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Chen ZC, Wang BY, Goldstein AK, Butt E, Mathieson K, Palanker D. Photovoltaic implant simulator reveals resolution limits in subretinal prosthesis. J Neural Eng 2022; 19:10.1088/1741-2552/ac8ed8. [PMID: 36055219 PMCID: PMC10752425 DOI: 10.1088/1741-2552/ac8ed8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 09/02/2022] [Indexed: 11/11/2022]
Abstract
Objective.PRIMA, the photovoltaic subretinal prosthesis, restores central vision in patients blinded by atrophic age-related macular degeneration (AMD), with a resolution closely matching the 100µm pixel size of the implant. Improvement in resolution requires smaller pixels, but the resultant electric field may not provide sufficient stimulation strength in the inner nuclear layer (INL) or may lead to excessive crosstalk between neighboring electrodes, resulting in low contrast stimulation patterns. We study the approaches to electric field shaping in the retina for prosthetic vision with higher resolution and improved contrast.Approach.We present a new computational framework, Retinal Prosthesis Simulator (RPSim), that efficiently computes the electric field in the retina generated by a photovoltaic implant with thousands of electrodes. Leveraging the PRIMA clinical results as a benchmark, we use RPSim to predict the stimulus strength and contrast of the electric field in the retina with various pixel designs and stimulation patterns.Main results.We demonstrate that by utilizing monopolar pixels as both anodes and cathodes to suppress crosstalk, most patients may achieve resolution no worse than 48µm. Closer proximity between the electrodes and the INL, achieved with pillar electrodes, enhances the stimulus strength and contrast and may enable 24µm resolution with 20µm pixels, at least in some patients.Significance.A resolution of 24µm on the retina corresponds to a visual acuity of 20/100, which is over 4 times higher than the current best prosthetic acuity of 20/438, promising a significant improvement of central vision for many AMD patients.
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Affiliation(s)
- Zhijie Charles Chen
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - Bing-Yi Wang
- Department of Physics, Stanford University, Stanford, CA, United States of America
| | - Anna Kochnev Goldstein
- Department of Electrical Engineering, Stanford University, Stanford, CA, United States of America
| | - Emma Butt
- Institute of Photonics, Department of Physics, University of Strathclyde, Glasgow, United Kingdom
| | - Keith Mathieson
- Institute of Photonics, Department of Physics, University of Strathclyde, Glasgow, United Kingdom
| | - Daniel Palanker
- Department of Ophthalmology, Stanford University, Stanford, CA, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, United States of America
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Stamp MEM, Tong W, Ganesan K, Prawer S, Ibbotson MR, Garrett DJ. 3D Diamond Electrode Array for High-Acuity Stimulation in Neural Tissue. ACS APPLIED BIO MATERIALS 2020; 3:1544-1552. [DOI: 10.1021/acsabm.9b01165] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Melanie E. M. Stamp
- School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Wei Tong
- School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria 3053, Australia
- Department of Optometry and Vision Sciences, Melbourne School of Health Sciences, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Kumaravelu Ganesan
- School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Steven Prawer
- School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Michael R. Ibbotson
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria 3053, Australia
| | - David J. Garrett
- School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
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Losada PG, Rousseau L, Grzeskowiak M, Valet M, Nguyen D, Dégardin J, Dubus E, Picaud S, Lissorgues G. Protuberant Electrode Structures for Subretinal Electrical Stimulation: Modeling, Fabrication and in vivo Evaluation. Front Neurosci 2019; 13:885. [PMID: 31507363 PMCID: PMC6718636 DOI: 10.3389/fnins.2019.00885] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Accepted: 08/07/2019] [Indexed: 11/13/2022] Open
Abstract
Many neural interfaces used for therapeutic applications are based on extracellular electrical stimulation to control cell polarization and thus functional activity. Amongst them, retinal implants have been designed to restore visual perception in blind patients affected by photoreceptor degeneration diseases, such as age-related macular degeneration (AMD) or retinitis pigmentosa (RP). While designing such a neural interface, several aspects must be taken into account, like the stimulation efficiency related to the current distribution within the tissue, the bio-interface optimization to improve resolution and tissue integration, and the material biocompatibility associated with long-term aging. In this study, we investigate the use of original microelectrode geometries for subretinal stimulation. The proposed structures combine the use of 3D wells with protuberant mushroom shaped electrode structures in the bottom, implemented on a flexible substrate that allows the in vivo implantation of the devices. These 3D microelectrode structures were first modeled using finite element analysis. Then, a specific microfabrication process compatible with flexible implants was developed to create the 3D microelectrode structures. These structures were tested in vivo to check the adaptation of the retinal tissue to them. Finally, preliminary in vivo stimulation experiments were performed.
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Affiliation(s)
| | - Lionel Rousseau
- Laboratory ESYCOM, University Paris Est-ESIEE-MLV, Noisy-le-Grand, France
| | | | - Manon Valet
- INSERM, CNRS, Institut de la Vision, Sorbonne Université, Paris, France
| | - Diep Nguyen
- INSERM, CNRS, Institut de la Vision, Sorbonne Université, Paris, France
| | - Julie Dégardin
- INSERM, CNRS, Institut de la Vision, Sorbonne Université, Paris, France
| | - Elisabeth Dubus
- INSERM, CNRS, Institut de la Vision, Sorbonne Université, Paris, France
| | - Serge Picaud
- INSERM, CNRS, Institut de la Vision, Sorbonne Université, Paris, France
| | - Gaelle Lissorgues
- Laboratory ESYCOM, University Paris Est-ESIEE-MLV, Noisy-le-Grand, France
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Kim C, Jeong J, Kim SJ. Recent Progress on Non-Conventional Microfabricated Probes for the Chronic Recording of Cortical Neural Activity. SENSORS (BASEL, SWITZERLAND) 2019; 19:E1069. [PMID: 30832357 PMCID: PMC6427797 DOI: 10.3390/s19051069] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 02/25/2019] [Accepted: 02/26/2019] [Indexed: 02/06/2023]
Abstract
Microfabrication technology for cortical interfaces has advanced rapidly over the past few decades for electrophysiological studies and neuroprosthetic devices offering the precise recording and stimulation of neural activity in the cortex. While various cortical microelectrode arrays have been extensively and successfully demonstrated in animal and clinical studies, there remains room for further improvement of the probe structure, materials, and fabrication technology, particularly for high-fidelity recording in chronic implantation. A variety of non-conventional probes featuring unique characteristics in their designs, materials and fabrication methods have been proposed to address the limitations of the conventional standard shank-type ("Utah-" or "Michigan-" type) devices. Such non-conventional probes include multi-sided arrays to avoid shielding and increase recording volumes, mesh- or thread-like arrays for minimized glial scarring and immune response, tube-type or cylindrical probes for three-dimensional (3D) recording and multi-modality, folded arrays for high conformability and 3D recording, self-softening or self-deployable probes for minimized tissue damage and extensions of the recording sites beyond gliosis, nanostructured probes to reduce the immune response, and cone-shaped electrodes for promoting tissue ingrowth and long-term recording stability. Herein, the recent progress with reference to the many different types of non-conventional arrays is reviewed while highlighting the challenges to be addressed and the microfabrication techniques necessary to implement such features.
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Affiliation(s)
- Chaebin Kim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Korea.
| | - Joonsoo Jeong
- Department of Biomedical Engineering, School of Medicine, Pusan National University, Yangsan 50612, Korea.
| | - Sung June Kim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Korea.
- Institute on Aging, College of Medicine, Seoul National University, Seoul 08826, Korea.
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Bareket L, Barriga-Rivera A, Zapf MP, Lovell NH, Suaning GJ. Progress in artificial vision through suprachoroidal retinal implants. J Neural Eng 2018; 14:045002. [PMID: 28541930 DOI: 10.1088/1741-2552/aa6cbb] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Retinal implants have proven their ability to restore visual sensation to people with degenerative retinopathy, characterized by photoreceptor cell death and the retina's inability to sense light. Retinal bionics operate by electrically stimulating the surviving neurons in the retina, thus triggering the transfer of visual sensory information to the brain. Suprachoroidal implants were first investigated in Australia in the 1950s. In this approach, the neuromodulation hardware is positioned between the sclera and the choroid, thus providing significant surgical and safety benefits for patients, with the potential to maintain residual vision combined with the artificial input from the device. Here we review the latest advances and state of the art devices for suprachoroidal prostheses, highlight future technologies and discuss challenges and perspectives towards improved rehabilitation of vision.
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Affiliation(s)
- Lilach Bareket
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
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Cheng DL, Greenberg PB, Borton DA. Advances in Retinal Prosthetic Research: A Systematic Review of Engineering and Clinical Characteristics of Current Prosthetic Initiatives. Curr Eye Res 2017; 42:334-347. [PMID: 28362177 DOI: 10.1080/02713683.2016.1270326] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PURPOSE To date, reviews of retinal prostheses have focused primarily on devices undergoing human trials in the Western Hemisphere and fail to capture significant advances in materials and engineering research in countries such as Japan and Korea, as well as projects in early stages of development. To address these gaps, this systematic review examines worldwide advances in retinal prosthetic research, evaluates engineering characteristics and clinical progress of contemporary device initiatives, and identifies potential directions for future research in the field of retinal prosthetics. METHODS A literature search using PubMed, Google Scholar, and IEEExplore was conducted following the PRISMA Guidelines for Systematic Review. Inclusion criteria were peer-reviewed papers demonstrating progress in human or animal trials and papers discussing the prosthetic engineering design. For each initiative, a description of the device, its engineering considerations, and recent clinical results were provided. RESULTS Ten prosthetic initiatives met our inclusion criteria and were organized by stimulation location. Of these initiatives, four have recently completed human trials, three are undergoing multi- or single-center human trials, and three are undergoing preclinical animal testing. Only the Argus II (FDA 2013, CE 2011) has obtained FDA approval for use in the United States; the Alpha-IMS (CE 2013) has achieved the highest visual acuity using a Landolt-C test to date and is the only device presently undergoing a multicenter clinical trial. CONCLUSION Several distinct approaches to retinal stimulation have been successful in eliciting visual precepts in animals and/or humans. However, many clinical needs are still not met and engineering challenges must be addressed before a retinal prosthesis with the capability to fully and safely restore functional vision can be realized.
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Affiliation(s)
- Derrick L Cheng
- a Alpert Medical School , Brown University , Providence , RI , USA
| | - Paul B Greenberg
- b Section of Ophthalmology , Providence VA Medical Center , Providence , RI , USA.,c Division of Ophthalmology, Alpert Medical School , Brown University , Providence , RI , USA
| | - David A Borton
- d School of Engineering , Brown University , Providence , RI , USA.,e Brown Institute for Brain Science , Brown University , Providence , RI , USA
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Jeong J, Bae SH, Min KS, Seo JM, Chung H, Kim SJ. A miniaturized, eye-conformable, and long-term reliable retinal prosthesis using monolithic fabrication of liquid crystal polymer (LCP). IEEE Trans Biomed Eng 2014; 62:982-9. [PMID: 25494496 DOI: 10.1109/tbme.2014.2377197] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A novel retinal prosthetic device was developed using biocompatible liquid crystal polymer (LCP) to address the problems associated with conventional metal- and polymer-based devices: the hermetic metal package is bulky, heavy, and labor-intensive, whereas a thin, flexible, and MEMS-compatible polymer-based system is not durable enough for chronic implantation. Exploiting the advantageous properties of LCP such as a low moisture absorption rate, thermobonding, and thermoforming, we fabricate a small, light-weight, long-term reliable retinal prosthesis that can be conformally attached on the eye-surface. A LCP fabrication process using monolithic integration and conformal deformation was established enabling miniaturization and a batch manufacturing process as well as eliminating the need for feed-through technology. The functionality of the fabricated device was tested through wireless operation in saline solution. Its efficacy and implantation stability were verified through in vivo animal tests by measuring the cortical potential and monitoring implanted dummy devices for more than a year, respectively.
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Guenther T, Lovell NH, Suaning GJ. Bionic vision: system architectures – a review. Expert Rev Med Devices 2014; 9:33-48. [DOI: 10.1586/erd.11.58] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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O'Brien EE, Greferath U, Vessey KA, Jobling AI, Fletcher EL. Electronic restoration of vision in those with photoreceptor degenerations. Clin Exp Optom 2012; 95:473-83. [PMID: 22823954 DOI: 10.1111/j.1444-0938.2012.00783.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 06/06/2012] [Accepted: 06/11/2012] [Indexed: 11/27/2022] Open
Abstract
Complete loss of vision is one of the most feared sequelae of retinal disease. Currently, there are few if any treatment options available to patients that may slow or prevent blindness in diseases caused by photoreceptor loss, such as retinitis pigmentosa and age-related macular degeneration. Electronic restoration of vision has emerged over recent years as a safe and viable option for those who have lost substantial numbers of photoreceptors and who are severely vision impaired. Indeed, there has been a dramatic increase in our understanding of what is required to restore vision using an electronic retinal prosthesis. Recent reports show that for some patients, restoration of vision to the point of reading large letters is possible. In this review, we examine the types of implants currently under investigation and the results these devices have achieved clinically. We then consider a range of engineering and biological factors that may need to be considered to improve the visual performance of newer-generation devices. With added research, it is hoped that the level of vision achieved with newer generation devices will steadily improve, resulting in enhanced quality of life for those with severe vision impairment.
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Affiliation(s)
- Emily E O'Brien
- Department of Anatomy and Cell Biology, The University of Melbourne, Parkville, Victoria, Australia.
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A novel in vitro sensing configuration for retinal physiology analysis of a sub-retinal prosthesis. SENSORS 2012; 12:3131-44. [PMID: 22736997 PMCID: PMC3376591 DOI: 10.3390/s120303131] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Revised: 02/27/2012] [Accepted: 02/27/2012] [Indexed: 11/16/2022]
Abstract
This paper presents a novel sensing configuration for retinal physiology analysis, using two microelectrode arrays (MEAs). In order to investigate an optimized stimulation protocol for a sub-retinal prosthesis, retinal photoreceptor cells are stimulated, and the response of retinal ganglion cells is recorded in an in vitro environment. For photoreceptor cell stimulation, a polyimide-substrate MEA is developed, using the microelectromechanical systems (MEMS) technology. For ganglion cell response recording, a conventional glass-substrate MEA is utilized. This new sensing configuration is used to record the response of retinal ganglion cells with respect to three different stimulation methods (monopolar, bipolar, and dual-monopolar stimulation methods). Results show that the geometrical relation between the stimulation microelectrode locations and the response locations seems very low. The threshold charges of the bipolar stimulation and the monopolar stimulation are in the range of 10∼20 nC. The threshold charge of the dual-monopolar stimulation is not obvious. These results provide useful guidelines for developing a sub-retinal prosthesis.
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Patel JN, Gray BL, Kaminska B, Gates BD. Flexible three-dimensional electrochemical glucose sensor with improved sensitivity realized in hybrid polymer microelectromechanical systems technique. J Diabetes Sci Technol 2011; 5:1036-43. [PMID: 22027295 PMCID: PMC3208858 DOI: 10.1177/193229681100500503] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Continuous glucose monitoring for patients with diabetes is of paramount importance to avoid severe health conditions resulting from hypoglycemia or hyperglycemia. Most available methods require an invasive setup and a health care professional. Handheld devices available on the market also require finger pricking for every measurement and do not provide continuous monitoring. Hence, continuous glucose monitoring from human tears using a glucose sensor embedded in a contact lens has been considered as a suitable option. However, the glucose concentration in human tears is very low in comparison with the blood glucose level (1/10-1/40 concentration). We propose a sensor that solves the sensitivity problem in a new way, is flexible, and is constructed onto the oxygen permeable contact lens material. METHODS To achieve such sensitivity while maintaining a small sensor footprint suitable for placement in a contact lens, we increased the active electrode area by using three-dimensional (3-D) electrode micropatterning. Fully flexible 3-D electrodes were realized utilizing ordered arrays of pillars with different shapes and heights. RESULTS We successfully fabricated square and cylindrical pillars with different height (50, 100, and 200 μm) and uniform metal coverage to realize sensor electrodes. The increased surface area produces high amperometric current that increases sensor sensitivity up to 300% using 200 μm tall square pillars. The sensitivity improvement closely follows the improvement in the surface area of the electrode. CONCLUSIONS The proposed flexible glucose sensors with 3-D microstructure electrodes are more sensitive to lower glucose concentrations and generate higher current signal than conventional glucose sensors.
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Affiliation(s)
- Jasbir N Patel
- School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, Canada.
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