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Ban S, Lee H, Chen J, Kim HS, Hu Y, Cho SJ, Yeo WH. Recent advances in implantable sensors and electronics using printable materials for advanced healthcare. Biosens Bioelectron 2024; 257:116302. [PMID: 38648705 DOI: 10.1016/j.bios.2024.116302] [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: 02/09/2024] [Revised: 03/20/2024] [Accepted: 04/16/2024] [Indexed: 04/25/2024]
Abstract
This review article focuses on the recent printing technological progress in healthcare, underscoring the significant potential of implantable devices across diverse applications. Printing technologies have widespread use in developing health monitoring devices, diagnostic systems, and surgical devices. Recent years have witnessed remarkable progress in fabricating low-profile implantable devices, driven by advancements in printing technologies and nanomaterials. The importance of implantable biosensors and bioelectronics is highlighted, specifically exploring printing tools using bio-printable inks for practical applications, including a detailed examination of fabrication processes and essential parameters. This review also justifies the need for mechanical and electrical compatibility between bioelectronics and biological tissues. In addition to technological aspects, this article delves into the importance of appropriate packaging methods to enhance implantable devices' performance, compatibility, and longevity, which are made possible by integrating cutting-edge printing technology. Collectively, we aim to shed light on the holistic landscape of implantable biosensors and bioelectronics, showcasing their evolving role in advancing healthcare through innovative printing technologies.
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Affiliation(s)
- Seunghyeb Ban
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30024, USA; IEN Center for Wearable Intelligent Systems and Healthcare at the Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Haran Lee
- Department of Mechanical Engineering, Chungnam National University, 99 Daehak-Ro, Yuseong-Gu, Daejeon, 34134, Republic of Korea
| | - Jiehao Chen
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30024, USA
| | - Hee-Seok Kim
- School of Engineering and Technology, University of Washington Tacoma, Tacoma, WA, 98195, USA
| | - Yuhang Hu
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30024, USA; School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Seong J Cho
- Department of Mechanical Engineering, Chungnam National University, 99 Daehak-Ro, Yuseong-Gu, Daejeon, 34134, Republic of Korea.
| | - Woon-Hong Yeo
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30024, USA; IEN Center for Wearable Intelligent Systems and Healthcare at the Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA, 30332, USA; Wallace H. Coulter Department of Biomedical Engineering, Georgia Tech and Emory University School of Medicine, Atlanta, GA, 30332, USA; Parker H. Petit Institute for Bioengineering and Biosciences, Institute for Materials, Institute for Robotics and Intelligent Machines, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
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2
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Nguyen KD, Dejean S, Nottelet B, Gautrot JE. Mechanical Evaluation of Hydrogel-Elastomer Interfaces Generated through Thiol-Ene Coupling. ACS APPLIED POLYMER MATERIALS 2023; 5:1364-1373. [PMID: 36817337 PMCID: PMC9926487 DOI: 10.1021/acsapm.2c01878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 01/06/2023] [Indexed: 06/18/2023]
Abstract
The formation of hybrid hydrogel-elastomer scaffolds is an attractive strategy for the formation of tissue engineering constructs and microfabricated platforms for advanced in vitro models. The emergence of thiol-ene coupling, in particular radical-based, for the engineering of cell-instructive hydrogels and the design of elastomers raises the possibility of mechanically integrating these structures without relying on the introduction of additional chemical moieties. However, the bonding of hydrogels (thiol-ene radical or more classic acrylate/methacrylate radical-based) to thiol-ene elastomers and alkene-functional elastomers has not been characterized in detail. In this study, we quantify the tensile mechanical properties of hybrid hydrogel samples formed of two elastomers bonded to a hydrogel material. We examine the impact of radical thiol-ene coupling on the crosslinking of both elastomers (silicone or polyesters) and hydrogels (based on thiol-ene crosslinking or diacrylate chemistry) and on the mechanics and failure behavior of the resulting hybrids. This study demonstrates the strong bonding of thiol-ene hydrogels to alkene-presenting elastomers with a range of chemistries, including silicones and polyesters. Overall, thiol-ene coupling appears as an attractive tool for the generation of strong, mechanically integrated, hybrid structures for a broad range of applications.
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Affiliation(s)
- Khai D.
Q. Nguyen
- Institute
of Bioengineering, Queen Mary, University
of London, Mile End Road, London E1 4NS, U.K.
- School
of Engineering and Materials Science, Queen
Mary, University of London, Mile End Road, London E1 4NS, U.K.
| | - Stéphane Dejean
- Polymers
for Health and Biomaterials, IBMM, Univ
Montpellier, CNRS, ENSCM, 34293 Montpellier, France
| | - Benjamin Nottelet
- Polymers
for Health and Biomaterials, IBMM, Univ
Montpellier, CNRS, ENSCM, 34293 Montpellier, France
| | - Julien E. Gautrot
- Institute
of Bioengineering, Queen Mary, University
of London, Mile End Road, London E1 4NS, U.K.
- School
of Engineering and Materials Science, Queen
Mary, University of London, Mile End Road, London E1 4NS, U.K.
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3
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Tripathy A, Regulagadda K, Lam CWE, Donati MA, Milionis A, Sharma CS, Mitridis E, Schutzius TM, Poulikakos D. Ultrathin Durable Organic Hydrophobic Coatings Enhancing Dropwise Condensation Heat Transfer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11296-11303. [PMID: 36037308 PMCID: PMC9494938 DOI: 10.1021/acs.langmuir.2c01477] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 08/17/2022] [Indexed: 06/15/2023]
Abstract
Organic hydrophobic layers targeting sustained dropwise condensation are highly desirable but suffer from poor chemical and mechanical stability, combined with low thermal conductivity. The requirement of such layers to remain ultrathin to minimize their inherent thermal resistance competes against durability considerations. Here, we investigate the long-term durability and enhanced heat-transfer performance of perfluorodecanethiol (PFDT) coatings compared to alternative organic coatings, namely, perfluorodecyltriethoxysilane (PFDTS) and perfluorodecyl acrylate (PFDA), the latter fabricated with initiated chemical vapor deposition (iCVD), in condensation heat transfer and under the challenging operating conditions of intense flow (up to 9 m s-1) of superheated steam (111 °C) at high pressures (1.42 bar). We find that the thiol coating clearly outperforms the silane coating in terms of both heat transfer and durability. In addition, despite being only a monolayer, it clearly also outperforms the iCVD-fabricated PFDA coating in terms of durability. Remarkably, the thiol layer exhibited dropwise condensation for at least 63 h (>2× times more than the PFDA coating, which survived for 30 h), without any visible deterioration, showcasing its hydrolytic stability. The cost of thiol functionalization per area was also the lowest as compared to all of the other surface hydrophobic treatments used in this study, thus making it the most efficient option for practical applications on copper substrates.
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Affiliation(s)
- Abinash Tripathy
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Kartik Regulagadda
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Cheuk Wing Edmond Lam
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Matteo A. Donati
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Athanasios Milionis
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Chander Shekhar Sharma
- Thermofluidics
Research Lab, Department of Mechanical Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab 140 001, India
| | - Efstratios Mitridis
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Thomas M. Schutzius
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
| | - Dimos Poulikakos
- Laboratory
of Thermodynamics in Emerging Technologies, Department of Mechanical
and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland
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McGlynn E, Nabaei V, Ren E, Galeote‐Checa G, Das R, Curia G, Heidari H. The Future of Neuroscience: Flexible and Wireless Implantable Neural Electronics. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2002693. [PMID: 34026431 PMCID: PMC8132070 DOI: 10.1002/advs.202002693] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 01/15/2021] [Indexed: 05/04/2023]
Abstract
Neurological diseases are a prevalent cause of global mortality and are of growing concern when considering an ageing global population. Traditional treatments are accompanied by serious side effects including repeated treatment sessions, invasive surgeries, or infections. For example, in the case of deep brain stimulation, large, stiff, and battery powered neural probes recruit thousands of neurons with each pulse, and can invoke a vigorous immune response. This paper presents challenges in engineering and neuroscience in developing miniaturized and biointegrated alternatives, in the form of microelectrode probes. Progress in design and topology of neural implants has shifted the goal post toward highly specific recording and stimulation, targeting small groups of neurons and reducing the foreign body response with biomimetic design principles. Implantable device design recommendations, fabrication techniques, and clinical evaluation of the impact flexible, integrated probes will have on the treatment of neurological disorders are provided in this report. The choice of biocompatible material dictates fabrication techniques as novel methods reduce the complexity of manufacture. Wireless power, the final hurdle to truly implantable neural interfaces, is discussed. These aspects are the driving force behind continued research: significant breakthroughs in any one of these areas will revolutionize the treatment of neurological disorders.
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Affiliation(s)
- Eve McGlynn
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Vahid Nabaei
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Elisa Ren
- Laboratory of Experimental Electroencephalography and NeurophysiologyDepartment of BiomedicalMetabolic and Neural SciencesUniversity of Modena and Reggio EmiliaModena41125Italy
| | - Gabriel Galeote‐Checa
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Rupam Das
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
| | - Giulia Curia
- Laboratory of Experimental Electroencephalography and NeurophysiologyDepartment of BiomedicalMetabolic and Neural SciencesUniversity of Modena and Reggio EmiliaModena41125Italy
| | - Hadi Heidari
- Microelectronics LabJames Watt School of EngineeringUniversity of GlasgowGlasgowG12 8QQUnited Kingdom
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5
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Wilson OR, McDaniel RM, Rivera AD, Magenau AJD. Alkylborane-Initiated Thiol-Ene Networks for the Synthesis of Thick and Highly Loaded Nanocomposites. ACS APPLIED MATERIALS & INTERFACES 2020; 12:55262-55268. [PMID: 33253524 DOI: 10.1021/acsami.0c16587] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Thiol-ene nanocomposites were synthesized for the first time using an alkylborane-ligand initiator complex under bulk and ambient conditions without external light or thermal stimuli. Initiation was triggered by the in situ decomplexation of an air-stable trialkylborane-amine complex to liberate trialkylborane, which rapidly autoxidizes with atmospheric oxygen and generates free radicals to drive thiol-ene polymerization. This chemically activated mode of initiation uniquely affords thiol-ene nanocomposites with an unrivaled carbon nanotube (CNT) loading of 1.3 wt % and thicknesses of ∼6.7 mm by circumventing restrictions imposed by long pathlengths and light-impeding fillers during photoinitiation. Alkylborane initiation also exhibited advantageous polymerization rates, equivalent to photoinitiation, resulting in network formation and gelation within minutes. Systematic studies were conducted to evaluate comparable alkylborane- and photo-initiated nanocomposites under progressively higher loadings and larger specimen thicknesses, revealing an enhancement or better retainment of mechanical performance in alkylborane-initiated nanocomposites.
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Affiliation(s)
- Olivia R Wilson
- Department of Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Riki M McDaniel
- Department of Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Arianna D Rivera
- Department of Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Andrew J D Magenau
- Department of Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
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6
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Electrical Properties of Thiol-ene-based Shape Memory Polymers Intended for Flexible Electronics. Polymers (Basel) 2019; 11:polym11050902. [PMID: 31108911 PMCID: PMC6571767 DOI: 10.3390/polym11050902] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 05/09/2019] [Accepted: 05/15/2019] [Indexed: 01/09/2023] Open
Abstract
Thiol-ene/acrylate-based shape memory polymers (SMPs) with tunable mechanical and thermomechanical properties are promising substrate materials for flexible electronics applications. These UV-curable polymer compositions can easily be polymerized onto pre-fabricated electronic components and can be molded into desired geometries to provide a shape-changing behavior or a tunable softness. Alternatively, SMPs may be prepared as a flat substrate, and electronic circuitry may be built directly on top by thin film processing technologies. Whichever way the final structure is produced, the operation of electronic circuits will be influenced by the electrical and mechanical properties of the underlying (and sometimes also encapsulating) SMP substrate. Here, we present electronic properties, such as permittivity and resistivity of a typical SMP composition that has a low glass transition temperature (between 40 and 60 °C dependent on the curing process) in different thermomechanical states of polymer. We fabricated parallel plate capacitors from a previously reported SMP composition (fully softening (FS)-SMP) using two different curing processes, and then we determined the electrical properties of relative permittivity and resistivity below and above the glass transition temperature. Our data shows that the curing process influenced the electrical permittivity, but not the electrical resistivity. Corona-Kelvin metrology evaluated the quality of the surface of FS-SMP spun on the wafer. Overall, FS-SMP demonstrates resistivity appropriate for use as an insulating material.
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7
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Okamura H, Yamagaki M, Nakata K. Analysis of Network Structures in Thiol-Ene UV Curing System Using Reworkable Resins. Polymers (Basel) 2018; 11:E5. [PMID: 30959989 PMCID: PMC6401966 DOI: 10.3390/polym11010005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 12/03/2022] Open
Abstract
An analysis of the network structures in thiol-ene UV curing resins was carried out using reworkable resins composed of di(meth)acrylate monomers having tertiary ester linkages. The effect of the functionality of the thiols, the functional ratio of the thiol and ene functions, their conversions and curing atmosphere on the chain lengths was discussed. A mixture of (meth)acrylates, thiol compounds, a photoradical initiator, and a photoacid generator was cured by irradiation at 365 nm. The cured samples were degraded by heating after irradiation at 254 nm. Size exclusion chromatography (SEC) and ¹H NMR analyses of the degraded samples were carried out after the methylation. The crosslinking conditions strongly affected the network structures. The degraded samples have molecular weights between 250 and 2700. The molecular weights of the degraded resins increased with the functionality of the thiol compounds. The chain length dependence suggests that thiol compounds with a high functionality have a low reactivity due to steric hindrance. The chain lengths of the degraded networks were nearly proportional to the concentration of the (meth)acrylate monomers. The addition of reactive diluents enhanced the reactivity and increased the chain length.
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Affiliation(s)
- Haruyuki Okamura
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
| | - Masashi Yamagaki
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
| | - Kyohei Nakata
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
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8
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Ecker M, Joshi-Imre A, Modi R, Frewin CL, Garcia-Sandoval A, Maeng J, Gutierrez-Heredia G, Pancrazio JJ, Voit WE. From softening polymers to multimaterial based bioelectronic devices. ACTA ACUST UNITED AC 2018. [DOI: 10.1088/2399-7532/aaed58] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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9
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González-González MA, Kanneganti A, Joshi-Imre A, Hernandez-Reynoso AG, Bendale G, Modi R, Ecker M, Khurram A, Cogan SF, Voit WE, Romero-Ortega MI. Thin Film Multi-Electrode Softening Cuffs for Selective Neuromodulation. Sci Rep 2018; 8:16390. [PMID: 30401906 PMCID: PMC6219541 DOI: 10.1038/s41598-018-34566-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 10/18/2018] [Indexed: 01/21/2023] Open
Abstract
Silicone nerve cuff electrodes are commonly implanted on relatively large and accessible somatic nerves as peripheral neural interfaces. While these cuff electrodes are soft (1–50 MPa), their self-closing mechanism requires of thick walls (200–600 µm), which in turn contribute to fibrotic tissue growth around and inside the device, compromising the neural interface. We report the use of thiol-ene/acrylate shape memory polymer (SMP) for the fabrication of thin film multi-electrode softening cuffs (MSC). We fabricated multi-size MSC with eight titanium nitride (TiN) electrodes ranging from 1.35 to 13.95 × 10−4 cm2 (1–3 kΩ) and eight smaller gold (Au) electrodes (3.3 × 10−5 cm2; 750 kΩ), that soften at physiological conditions to a modulus of 550 MPa. While the SMP material is not as soft as silicone, the flexural forces of the SMP cuff are about 70–700 times lower in the MSC devices due to the 30 μm thick film compared to the 600 μm thick walls of the silicone cuffs. We demonstrated the efficacy of the MSC to record neural signals from rat sciatic and pelvic nerves (1000 µm and 200 µm diameter, respectively), and the selective fascicular stimulation by current steering. When implanted side-by-side and histologically compared 30 days thereafter, the MSC devices showed significantly less inflammation, indicated by a 70–80% reduction in ED1 positive macrophages, and 54–56% less fibrotic vimentin immunoreactivity. Together, the data supports the use of MSC as compliant and adaptable technology for the interfacing of somatic and autonomic peripheral nerves.
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Affiliation(s)
- María A González-González
- Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Aswini Kanneganti
- Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Alexandra Joshi-Imre
- Department of Material Science and Engineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Ana G Hernandez-Reynoso
- Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Geetanjali Bendale
- Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Romil Modi
- Department of Material Science and Engineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Melanie Ecker
- Department of Material Science and Engineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Ali Khurram
- Department of Material Science and Engineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Stuart F Cogan
- Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Walter E Voit
- Department of Material Science and Engineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Mario I Romero-Ortega
- Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA.
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10
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Shoffstall AJ, Ecker M, Danda V, Joshi-Imre A, Stiller A, Yu M, Paiz JE, Mancuso E, Bedell HW, Voit WE, Pancrazio JJ, Capadona JR. Characterization of the Neuroinflammatory Response to Thiol-ene Shape Memory Polymer Coated Intracortical Microelectrodes. MICROMACHINES 2018; 9:E486. [PMID: 30424419 PMCID: PMC6215215 DOI: 10.3390/mi9100486] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 09/11/2018] [Accepted: 09/18/2018] [Indexed: 01/10/2023]
Abstract
Thiol-ene based shape memory polymers (SMPs) have been developed for use as intracortical microelectrode substrates. The unique chemistry provides precise control over the mechanical and thermal glass-transition properties. As a result, SMP substrates are stiff at room temperature, allowing for insertion into the brain without buckling and subsequently soften in response to body temperatures, reducing the mechanical mismatch between device and tissue. Since the surface chemistry of the materials can contribute significantly to the ultimate biocompatibility, as a first step in the characterization of our SMPs, we sought to isolate the biological response to the implanted material surface without regards to the softening mechanics. To accomplish this, we tightly controlled for bulk stiffness by comparing bare silicon 'dummy' devices to thickness-matched silicon devices dip-coated with SMP. The neuroinflammatory response was evaluated after devices were implanted in the rat cortex for 2 or 16 weeks. We observed no differences in the markers tested at either time point, except that astrocytic scarring was significantly reduced for the dip-coated implants at 16 weeks. The surface properties of non-softening thiol-ene SMP substrates appeared to be equally-tolerated and just as suitable as silicon for neural implant substrates for applications such as intracortical microelectrodes, laying the groundwork for future softer devices to improve upon the prototype device performance presented here.
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Affiliation(s)
- Andrew J Shoffstall
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
- Advanced Platform Technology Center, Rehabilitation Research and Development, Louis Stokes Cleveland Department of Veteran Affairs Medical Center, Cleveland, OH, USA.
| | - Melanie Ecker
- Advanced Platform Technology Center, Rehabilitation Research and Development, Louis Stokes Cleveland Department of Veteran Affairs Medical Center, Cleveland, OH, USA.
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, USA.
| | - Vindhya Danda
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, USA.
- Center for Engineering Innovation, The University of Texas at Dallas, Richardson, TX, USA.
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, USA.
- Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX, USA.
| | - Alexandra Joshi-Imre
- Center for Engineering Innovation, The University of Texas at Dallas, Richardson, TX, USA.
| | - Allison Stiller
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, USA.
| | - Marina Yu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
- Advanced Platform Technology Center, Rehabilitation Research and Development, Louis Stokes Cleveland Department of Veteran Affairs Medical Center, Cleveland, OH, USA.
| | - Jennifer E Paiz
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
- Advanced Platform Technology Center, Rehabilitation Research and Development, Louis Stokes Cleveland Department of Veteran Affairs Medical Center, Cleveland, OH, USA.
| | - Elizabeth Mancuso
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
- Advanced Platform Technology Center, Rehabilitation Research and Development, Louis Stokes Cleveland Department of Veteran Affairs Medical Center, Cleveland, OH, USA.
| | - Hillary W Bedell
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
| | - Walter E Voit
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, USA.
- Center for Engineering Innovation, The University of Texas at Dallas, Richardson, TX, USA.
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, USA.
- Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX, USA.
| | - Joseph J Pancrazio
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, USA.
| | - Jeffrey R Capadona
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
- Advanced Platform Technology Center, Rehabilitation Research and Development, Louis Stokes Cleveland Department of Veteran Affairs Medical Center, Cleveland, OH, USA.
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11
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Bernardin EK, Frewin CL, Everly R, Ul Hassan J, Saddow SE. Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface. MICROMACHINES 2018; 9:E412. [PMID: 30424345 PMCID: PMC6187288 DOI: 10.3390/mi9080412] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 08/11/2018] [Accepted: 08/12/2018] [Indexed: 01/09/2023]
Abstract
Intracortical neural interfaces (INI) have made impressive progress in recent years but still display questionable long-term reliability. Here, we report on the development and characterization of highly resilient monolithic silicon carbide (SiC) neural devices. SiC is a physically robust, biocompatible, and chemically inert semiconductor. The device support was micromachined from p-type SiC with conductors created from n-type SiC, simultaneously providing electrical isolation through the resulting p-n junction. Electrodes possessed geometric surface area (GSA) varying from 496 to 500 K μm². Electrical characterization showed high-performance p-n diode behavior, with typical turn-on voltages of ~2.3 V and reverse bias leakage below 1 nArms. Current leakage between adjacent electrodes was ~7.5 nArms over a voltage range of -50 V to 50 V. The devices interacted electrochemically with a purely capacitive relationship at frequencies less than 10 kHz. Electrode impedance ranged from 675 ± 130 kΩ (GSA = 496 µm²) to 46.5 ± 4.80 kΩ (GSA = 500 K µm²). Since the all-SiC devices rely on the integration of only robust and highly compatible SiC material, they offer a promising solution to probe delamination and biological rejection associated with the use of multiple materials used in many current INI devices.
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Affiliation(s)
- Evans K Bernardin
- Department of Biomedical Engineering, University of South Florida, Tampa, FL 33620, USA.
| | - Christopher L Frewin
- Department of Bioengineering, University of Texas at Dallas, Dallas, TX 75080, USA.
| | - Richard Everly
- Nanotechnology Research and Education Center @ USF, Tampa, FL 33617, USA.
| | - Jawad Ul Hassan
- Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.
| | - Stephen E Saddow
- Department of Electrical Engineering, University of South Florida, Tampa, FL 33620, USA.
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Do DH, Ecker M, Voit WE. Characterization of a Thiol-Ene/Acrylate-Based Polymer for Neuroprosthetic Implants. ACS OMEGA 2017; 2:4604-4611. [PMID: 30023725 PMCID: PMC6044618 DOI: 10.1021/acsomega.7b00834] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/04/2017] [Indexed: 05/18/2023]
Abstract
Thiol-ene/acrylate shape-memory polymers can be used as base substrates for neural electrodes to treat neurological dysfunction. Neural electrodes are implanted into the body to alter or record impulse conduction. This study characterizes thiol-ene/acrylate polymers to determine which synthesis methods constitute an ideal substrate for neural implants. To achieve a desired Tg between 50 and 56.5 °C, curing conditions, polymer thickness, monomer ratios, and water uptake were all examined and controlled for. Characterization with dynamic mechanical analysis and thermal gravimetric analysis reveals that thin, thiol-ene/acrylate polymers composed of at least 50 mol % acrylate content and cured for at least 1 h at 365 nm are promising as substrates for neural electrodes.
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Affiliation(s)
- Dang-Huy Do
- Department
of Biological Sciences and Department of Materials Science
and Engineering, The University of Texas
at Dallas, 800 W Campbell Road, Richardson, Texas 75080, United
States
| | - Melanie Ecker
- Department
of Biological Sciences and Department of Materials Science
and Engineering, The University of Texas
at Dallas, 800 W Campbell Road, Richardson, Texas 75080, United
States
| | - Walter E. Voit
- Department
of Biological Sciences and Department of Materials Science
and Engineering, The University of Texas
at Dallas, 800 W Campbell Road, Richardson, Texas 75080, United
States
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Reit R, Abitz H, Reddy N, Parker S, Wei A, Aragon N, Ho M, Weittenhiller A, Kang T, Ecker M, Voit WE. Thiol-epoxy/maleimide ternary networks as softening substrates for flexible electronics. J Mater Chem B 2016; 4:5367-5374. [PMID: 32263460 DOI: 10.1039/c6tb01082b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Softening microelectrode arrays, or flexible bioelectronic systems which can dynamically change modulus under the application of an external stimulus such as heat or electromagnetic radiation, have been of significant interest in the literature within the previous decade. Through their ability to actively soften in vivo, these devices have shown the capacity to attenuate the neuronal damage associated with insertion of rigid microelectrode arrays into soft tissue. Thiol-click substrates specifically have shown particularly impressive results for fabricating devices requiring small-scale, high-performance electronics for neural recording. However, previous attempts to engineer increasingly lower-modulus substrates for these devices have failed due to the fundamental chemistries' (the thioether linkage) flexibility. This failure has led to substrates without sufficient mechanical rigidity for penetrating soft tissue at physiological temperatures, or sufficient softening capacity to reduce the mechanical mismatch between soft tissue and implantable device. In this work, a ternary thiol-epoxy/maleimide network is investigated as a potential substrate materials space in which the degree of softening can be modulated without sacrificing the mechanical rigidity at physiological temperatures. Using these networks as platforms for the microfabrication of electrode arrays, example implantable intracortical microelectrode arrays are fabricated on both thiol-epoxy and thiol-epoxy/maleimide networks to demonstrate the insertion capacity of microelectrode arrays on the ternary polymer networks.
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Affiliation(s)
- Radu Reit
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX 75030, USA.
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