Chronic softening spinal cord stimulation arrays

Garcia-Sandoval, Aldo; Pal, Ajay; Mishra, Asht M.; Sherman, Sydney E; Parikh, Ankit; Joshi‐Imre, Alexandra; Arreaga-Salas, David; Gutiérrez-Heredia, Gerardo; Duran-Martinez, Adriana C.; Nathan, Jordan; Hosseini, Seyed Mahmoud; Carmel, Jason B.; Voit, Walter

doi:10.1088/1741-2552/aab90d

Cited by 40 publications

(30 citation statements)

References 41 publications

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“…In conclusion, thiol-ene and thiol-ene/acrylate shape memory polymers are currently under development for a wide range of neural implant applications, including intracortical microelectrodes, spinal cord stimulators, sciatic-tibial-sural ‘Y’ electrodes, longitudinal intrafascicular electrodes, and self-coiling nerve cuff electrodes [ 22 , 35 , 40 , 78 , 79 , 80 ]. Here, our initial study sought to investigate the foreign body response to the material in absence of its mechanical softening properties so that as many extra and potentially confounding variables as possible could be eliminated.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Neuroinflammatory Response to Thiol-ene Shape Memory Polymer Coated Intracortical Microelectrodes

et al. 2018

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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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Section: Discussionmentioning

confidence: 99%

Characterization of the Neuroinflammatory Response to Thiol-ene Shape Memory Polymer Coated Intracortical Microelectrodes

et al. 2018

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“…The ultimate goal is to utilize the hydrolytically stable SMP-A as a substrate for neural interfaces and therefore have an alternative to the currently used softeing SMP versions (Simon et al, 2017;Garcia-Sandoval et al, 2018). To validate that the polymer is compatible with microfabrication processes, SMP-A was spin-coated on silicon wafers and subjected to photolithography as previously decribed (Ecker et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

“…Subsequently, oxygen plasma was applied to remove excess polymer and patterned photoresist. Finally, the sample was etched with hydrofluoric acid to remove SiN that was on the SMP (Garcia-Sandoval et al, 2018). The micro-fabricated pacifier probes were also used for the in vitro cytotoxicity test.…”

Section: Discussionmentioning

confidence: 99%

“…Here, we present a thiol-ene SMP formulation that is chemically and structurally similar to the most recent ones, but does not contain any ester groups (Do et al, 2017;Ecker et al, 2017;Simon et al, 2017;Garcia-Sandoval et al, 2018;Shoffstall et al, 2018). We have optimized the synthesis of a new monomer and tailored the polymer composition to have similar in vivo softening capabilities as previous reported SMPs.…”

Section: Introductionmentioning

confidence: 99%

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Softening Shape Memory Polymer Substrates for Bioelectronic Devices With Improved Hydrolytic Stability

et al. 2018

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Candidate materials for next generation neural recording electrodes include shape memory polymers (SMPs). These materials have the capability to undergo softening after insertion in the body, and therefore reduce the mismatch in modulus that usually exists between the device and the tissue. Current SMP formulations, which have shown promise for neural implants, contain ester groups within the main chain of the polymer and are therefore prone to hydrolytic decomposition under physiological conditions over periods of 11-13 months in vivo, thus limiting the utility for chronic applications. Ester free polymers are stable in harsh condition (PBS at 75 • C or NaOH at 37 • C) and accelerated aging results suggest that ester free SMPs are projected to be stable under physiological condition for at least 7 years. In addition, the ester free SMP is compatible with microfabrication processes needed for device fabrication. Furthermore, they demonstrate in vitro biocompatibility as demonstrated by high levels of cell viability from ISO 10993 testing.

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“…A wide range of biological phenomena can be observed with one or a matrix of extracellular electrodes . In addition, the same electrode may be used to deliver electrical stimulation to a local area of the tissue . To achieve higher resolution activity mapping, the number and density of electrodes are increased so that simultaneous recordings from a population of cells are collected with high temporal responses .…”

Section: Function and Compliance Of Bioelectronic Systemsmentioning

confidence: 99%

Conformable Hybrid Systems for Implantable Bioelectronic Interfaces

2019

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of Things (IoT) to wellness and medical technologies. In the past decade, significant efforts have been deployed to exploit these technologies to design and manufacture conformable bioelectronic interfaces.Mechanical compliance is a critical specification for the long-term integration of on-skin devices and implants with a biological host. The latter is largely composed of soft tissues, with Young's moduli E in the range from 100 Pa to 10 MPa (excluding bones and cartilage), [1] and sustains different physiological dynamic behaviors, e.g., repeated displacements of hundreds of micrometers at 1 Hz in the heart or brain, [2] volumetric changes up to 8% in the heart, [3] or large flexion and angular displacement in the skin or spinal cord. [4] In contrast, electronic materials are stiff, with the elastic modulus in the range of 1 GPa (organic materials) to 100 GPa (inorganic materials) and rigid, bearing little strain without displaying mechanical failure or defect generation. Interfaces between such disparate biological and man-made materials suffer therefore from a mechanical mismatch that hinders reliable and continued device function in the body. [1,5] Several approaches have been used to engineer mechanical compliance within an electronic device or circuit. [6] Outcomes of such conformable circuits include improved mitigation of foreign body reaction (FBR) in vivo compared to rigid interfaces, [7] access to so far unreachable regions, [8] and bidirectional communication with high spatiotemporal resolution with the biological host.Monolithic integration of electronic devices and circuits on semiconductor wafers offers extreme miniaturization and very high device density (e.g., >10 8 transistors mm −2 , Intel FinFET Technology nodes [9] ). Such large scale of integration cannot be achieved for electronics prepared on conformable carrier substrates, as this class of devices employs lower performance device materials and polymeric substrates with low chemical and/or thermal stability leading to limited lithographic resolution and large transistor sizes. These constraints typically worsen as the compliance of the substrate increases. Some of the highest device densities reported to date are >10 000 cm −2 on flexible substrate [10] and 347 cm −2 on stretchable carrier. [11] Conformable hybrid systems leverage the performance of standard complementary metal-oxide-semiconductor integrated circuits (ICs) and the compliance of discrete flexible or stretchable components and carriers, to effectively provide high-performance and mechanically compliant electronic circuits. They call for new Conformable bioelectronic systems are promising tools that may aid the understanding of diseases, alleviate pathological symptoms such as chronic pain, heart arrhythmia, and dysfunctions, and assist in reversing conditions such as deafness, blindness, and paralysis. Combining reduced invasiveness with advanced electronic functions, hybrid bioelectronic systems have evolved tremendously in the last decade, pushed by progress in materials ...

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Chronic softening spinal cord stimulation arrays

Abstract: Softening SCS arrays meet the needs for research-grade devices in rats and could be developed into human devices in the future.

Cited by 40 publications

References 41 publications

Characterization of the Neuroinflammatory Response to Thiol-ene Shape Memory Polymer Coated Intracortical Microelectrodes

Characterization of the Neuroinflammatory Response to Thiol-ene Shape Memory Polymer Coated Intracortical Microelectrodes

Softening Shape Memory Polymer Substrates for Bioelectronic Devices With Improved Hydrolytic Stability

Conformable Hybrid Systems for Implantable Bioelectronic Interfaces

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