3D Parylene sheath neural probe for chronic recordings

Kim, B J; Kuo, Jen-Tsai; Hara, Seth A.; Lee, C D; Liu, Yu; Gutierrez, Christian; Hoang, Tuan; Pikov, Victor; Meng, Ellis

doi:10.1088/1741-2560/10/4/045002

Cited by 134 publications

(160 citation statements)

References 59 publications

(65 reference statements)

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“…And for the smallest chronically implantable extracellular microelectrode so far reported — an electrode with a 15 µm 2 cross-sectional area 173 — two-photon imaging surrounding the implant revealed a lack of astrogliosis and minimal disruption of the vasculature. However, reduced stiffness can make softer 156,174 and subcellular devices 48,68,175 difficult to implant, requiring the use of an insertion tool 175,176 or dissolvable shuttle 177,178 . Since new device designs often employ both softer materials and reduced feature sizes, the relative impact of each of these factors on the tissue response can be difficult to interpret.…”

Section: Glial-activation Challenges and Design Considerationsmentioning

confidence: 99%

Glial responses to implanted electrodes in the brain

et al. 2017

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The use of implants that can electrically stimulate or record electrophysiological or neurochemical activity in nervous tissue is rapidly expanding. Despite remarkable results in clinical studies and increasing market approvals, the mechanisms underlying the therapeutic effects of neuroprosthetic and neuromodulation devices, as well as their side effects and reasons for their failure, remain poorly understood. A major assumption has been that the signal-generating neurons are the only important target cells of neural-interface technologies. However, recent evidence indicates that the supporting glial cells remodel the structure and function of neuronal networks and are an effector of stimulation-based therapy. Here, we reframe the traditional view of glia as a passive barrier, and discuss their role as an active determinant of the outcomes of device implantation. We also discuss the implications that this has on the development of bioelectronic medical devices.

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Section: Glial-activation Challenges and Design Considerationsmentioning

confidence: 99%

Glial responses to implanted electrodes in the brain

et al. 2017

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“…Although this increase does not affect the functionality of these thermoformed implantable devices [33], the thermoforming process has demonstrated these changes to the sensitive electrode surface that can be explained by a smoothing of the electrode surface during annealing [46] as well as possible mobilized chlorine adsorption on the surface during annealing [50,51] observed in literature. Additional work is underway in ascertaining the source of these changes.…”

Section: Electrochemical Effectsmentioning

confidence: 70%

Formation of three-dimensional Parylene C structures via thermoforming

Kim

Chen

Gupta

et al. 2014

J. Micromech. Microeng.

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The thermoplastic nature of Parylene C is leveraged to enable the formation of three-dimensional structures using a thermal forming (thermoforming) technique. Thermoforming involves the heating of Parylene films above its glass transition temperature while they are physically confined in the final desired conformation. Micro and macro scale three-dimensional structures composed of Parylene thin films were developed using the thermoforming process, and the resulting chemical and mechanical changes to the films were characterized. No large changes to the surface and bulk chemistries of the polymer were observed following the thermoforming process conducted in vacuum. Heat treated structures exhibited increased stiffness by a maximum of 37% depending on the treatment temperature, due to an increase in crystallinity of the Parylene polymer. This study revealed important property changes resulting from the process, namely (1) the development of high strains in thermoformed areas of small radii of curvature (30-90 µm) and (2) ∼1.5% bulk material shrinkage in thermoformed multilayered Parylene-Parylene and Parylene-metal-Parylene films. Thermoforming is a simple process whereby three-dimensional structures can be achieved from Parylene C-based thin film structures with tunable mechanical properties as a function of treatment temperature.

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“…Histological studies (Biran et al, 2007;Kim et al, 2004) report that the strain induced immune response, caused by the rigid tethering of the electrode to the skull, leads to an increase in microglial activity in the implanted tissue as compared to untethered electrodes (Gilletti and Muthuswamy, 2006). Quantitative studies have shown that electrode with low Young's modulus material or redefined geometry for high compliance can provide front-end strain relief and polymers such as polyimide and Parylene-C, with their good biocompatibility, have been the choice of researchers for electrode substrate materials (Sankar et al, 2013;Seymour et al, 2011;Ziegler Contents Kim, 2013;Rodger et al, 2008;Metallo et al, 2011). Furthermore it is well known that the miniaturization of the electrode size is a critical requirement for single neuron recording and for electrical stimulation restricted to small populations of neuronal elements.…”

Section: Introductionmentioning

confidence: 99%