Conformable neural interface based on off-stoichiometry thiol-ene-epoxy thermosets

Borda, Eleonora; Leccardi, Marta Jole Ildelfonsa Airaghi; Zollinger, Elodie Geneviève; Ghezzi, Diego

doi:10.1016/j.biomaterials.2022.121979

Cited by 11 publications

(12 citation statements)

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“…Other biocompatible photoinitiators are also under development for future applications 47 . In addition, other materials such as thiol-ene-epoxy thermosets can be included in the fabrication process to promote longevity and maintain conformability 48 .…”

Section: Discussionmentioning

confidence: 99%

Full-field, conformal epiretinal electrode array using hydrogel and polymer hybrid technology

Zhou¹,

Young²,

Valle³

et al. 2023

Sci Rep

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Shape-morphable electrode arrays can form 3D surfaces to conform to complex neural anatomy and provide consistent positioning needed for next-generation neural interfaces. Retinal prostheses need a curved interface to match the spherical eye and a coverage of several cm to restore peripheral vision. We fabricated a full-field array that can (1) cover a visual field of 57° based on electrode position and of 113° based on the substrate size; (2) fold to form a compact shape for implantation; (3) self-deploy into a curvature fitting the eye after implantation. The full-field array consists of multiple polymer layers, specifically, a sandwich structure of elastomer/polyimide-based-electrode/elastomer, coated on one side with hydrogel. Electrodeposition of high-surface-area platinum/iridium alloy significantly improved the electrical properties of the electrodes. Hydrogel over-coating reduced electrode performance, but the electrodes retained better properties than those without platinum/iridium. The full-field array was rolled into a compact shape and, once implanted into ex vivo pig eyes, restored to a 3D curved surface. The full-field retinal array provides significant coverage of the retina while allowing surgical implantation through an incision 33% of the final device diameter. The shape-changing material platform can be used with other neural interfaces that require conformability to complex neuroanatomy.

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Section: Discussionmentioning

confidence: 99%

Full-field, conformal epiretinal electrode array using hydrogel and polymer hybrid technology

Zhou¹,

Young²,

Valle³

et al. 2023

Sci Rep

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“…[ 42 ] Recently, off‐stoichiometry thiol‐ene‐epoxy (OSTE+) thermosets have shown to be an excellent compromise between compliance with clean‐room processes, including UV patterning, and mechanical compliance, including low elastic modulus (MPa range) and elastic deformation (>20%). [ 27 ]…”

Section: Figurementioning

confidence: 99%

“…including UV patterning, and mechanical compliance, including low elastic modulus (MPa range) and elastic deformation (>20%). [27] Besides flexibility and softness, the total device size and volume can significantly reduce the FBR severity. Smaller devices will likely preserve tissue homeostasis during insertion, reduce tissue displacement and decrease tissue compression.…”

mentioning

confidence: 99%

“…OSTEþ is a valuable alternative to other polymeric layers because of its low permeability to gases and molecules. [27,90] If the device failure is unavoidable, the emergence of transient electronics adds a new asset to the neurotechnology toolbox. [91] Transient, biodegradable, and implantable devices eliminate the need for surgical retrieval caused by infection or malfunctioning.…”

mentioning

confidence: 99%

“…Therefore, polydimethylsiloxane (PDMS), polyurethane, and other elastomers have been exploited in conformable and stretchable neural interfaces layered on nerves, the spinal cord, the retina, and the brain (Figure 1c,d). [29][30][31][32][33][34][35] However, performing conventional clean-room processes on PDMS is an open challenge, mainly because of the different thermal expansion coefficients between metals and PDMS [36] and limitations in the encapsulation step, [27] which is usually done manually or by reactive-ion etching to obtain smaller features but with the risk of leaving toxic residues. [37] Alternatively, ultra-soft hydrogels have been investigated.…”

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confidence: 99%

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Engineering Materials for Neurotechnology

Ghezzi

2023

Adv Eng Mater

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A crucial issue for a neural interface is the chronic foreign body reaction (FBR) upon implantation. [1][2][3] Avoiding the FBR, or at least reducing its severity, is necessary to preserve the long-term functioning of neural interfaces. [4][5][6] Yet, this is still an open research question. The FBR is traditionally described as a passive barrier encapsulating the device, altering the neural interface, and impairing implant-to-cell communication. [2,7,8] Besides acting as a passive insulating barrier, soluble factors released during the inflammatory and fibrotic process can accelerate device degradation and electrode corrosion. [9] The FBR is inevitable whenever any material becomes in contact with body fluids. [10] In contrast, materials engineering and advanced fabrication processes can minimize its severity, for example, by improving the mechanical compliance of the implant, decreasing the device size, and reducing implantation and chronic trauma. [3] One of the most common limitations of neural interfaces is the mechanical mismatch between the stiff neural implant and the soft neural tissue. This mismatch intensifies the neural damage and FBR caused by insertion, compression, and motion. [11] The neural tissue is curved, soft, dynamic, and subject to deformations caused, for example, by blood pulsation, respiratory pressure, and natural body movements. [11,12] By contrast, most neural interfaces are static and struggle to conform to neural tissue in static and dynamic conditions. A large body of research in neural interfaces addresses this issue using flexible, conformable, or stretchable neural interfaces (Figure 1).Polyimide (PI), parylene-C, and SU-8 are widely used materials in flexible neural interfaces. [13][14][15][16][17][18][19][20][21][22] The advantages of these materials are their biochemical and thermal stability, and their compatibility with clean-room microfabrication processes. [23][24][25] However, they exhibit high Young's modulus (GPa range) and limited elastic deformation (<3%). [26] Ultra-thin neural interfaces made of these materials still reach low bending stiffness if sufficiently thin (<15 μm) despite the high Young's modulus. [27] They can conform to a cylindrical body such as a nerve or a smooth brain surface (Figure 1a), thus reducing the FBR severity. [23] Moreover, ultra-thin neural interfaces with a small cross-sectional area also can minimize tissue damage during penetration (Figure 1b). [22,24,28] Conformability to cylindrical or smooth surfaces is sufficient in rodents, but more is needed for large and complex surfaces with gyri, like in primates, where spherical conformability is required. Because of the limited elastic deformation, conformability to convoluted surfaces is difficult to achieve with these materials. Compliance with neural macro-and micro-movements is also reduced. [26] Elastomers exhibit a lower Young's modulus of at least three orders of magnitude (MPa range) and a much broader elastic regime under strain (>20%). Bending stiffness is influenced by both thick...

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Poly(3,4‐Ethylenedioxythiophene)/Functional Gold Nanoparticle films for Improving the Electrode‐Neural Interface

Wu,

Wang,

Yan

et al. 2024

Adv Healthcare Materials

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Implantable neural electrodes are indispensable tools for recording neuron activity, playing a crucial role in neuroscience research. However, traditional neural electrodes suffer from limited electrochemical performance, compromised biocompatibility, and tentative stability, posing great challenges for reliable long‐term studies in free‐moving animals. In this study, we present a novel approach employing a hybrid film composed of poly(3,4‐ethylenedioxythiophene)/functional gold nanoparticles (PEDOT/3‐MPA‐Au) to improve the electrode‐neural interface. The deposited PEDOT/3‐MPA‐Au demonstrates superior cathodal charge storage capacity, reduced electrochemical impedance, and remarkable electrochemical and mechanical stability. Upon implantation into the cortex of mice for a duration of 12 weeks, the modified electrodes exhibit notably decreased levels of glial fibrillary acidic protein and increased neuronal nuclei immunostaining compared to counterparts utilizing poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonate). Additionally, the PEDOT/3‐MPA‐Au modified electrodes consistently capture high‐quality, stable long‐term electrophysiological signals in vivo, enabling continuous recording of target neurons for up to 16 weeks. This innovative modification strategy offers a promising solution for fabricating low‐impedance, tissue‐friendly, and long‐term stable neural interfaces, thereby addressing the shortcomings of conventional neural electrodes. These findings mark a significant advancement towards the development of more reliable and efficacious neural interfaces, with broad implications for both research and clinical applications.This article is protected by copyright. All rights reserved

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Conformable neural interface based on off-stoichiometry thiol-ene-epoxy thermosets

Cited by 11 publications

References 74 publications

Full-field, conformal epiretinal electrode array using hydrogel and polymer hybrid technology

Full-field, conformal epiretinal electrode array using hydrogel and polymer hybrid technology

Engineering Materials for Neurotechnology

Poly(3,4‐Ethylenedioxythiophene)/Functional Gold Nanoparticle films for Improving the Electrode‐Neural Interface

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