Achieving Ultra-Conformability With Polyimide-Based ECoG Arrays

Vomero, Maria; Cruz, Maria Francisca Porto; Zucchini, Elena; Shabanian, Ardavan; Delfino, Emanuela; Carli, Stefano; Fadiga, Luciano; Ricci, Davide

doi:10.1109/embc.2018.8513171

Cited by 11 publications

(10 citation statements)

References 12 publications

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“…The ultra-flexible ECoG devices with GC electrodes were successfully manufactured following the microfabrication steps listed in Figure 2. To ensure a good interlock of the materials (i.e., GC, PI and Pt), DLC and SiC were used as adhesion promoters [15,16] and—to achieve conformability of the devices over the curvilinear rat brains—the total thickness of the PI was set at 8 µm [29] and the electrode area was designed in a finger-like manner. Each finger was additionally designed to incorporate holes—and thus to be ‘breathable’—to allow the diffusion of biological fluids through the devices and improve the tissue-electrode contact.…”

Section: Resultsmentioning

confidence: 99%

Glassy Carbon Electrocorticography Electrodes on Ultra-Thin and Finger-Like Polyimide Substrate: Performance Evaluation Based on Different Electrode Diameters

et al. 2018

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Glassy carbon (GC) has high potential to serve as a biomaterial in neural applications because it is biocompatible, electrochemically inert and can be incorporated in polyimide-based implantable devices. Miniaturization and applicability of GC is, however, thought to be partially limited by its electrical conductivity. For this study, ultra-conformable polyimide-based electrocorticography (ECoG) devices with different-diameter GC electrodes were fabricated and tested in vitro and in rat models. For achieving conformability to the rat brain, polyimide was patterned in a finger-like shape and its thickness was set to 8 µm. To investigate different electrode sizes, each ECoG device was assigned electrodes with diameters of 50, 100, 200 and 300 µm. They were electrochemically characterized and subjected to 10 million biphasic pulses—for achieving a steady-state—and to X-ray photoelectron spectroscopy, for examining their elemental composition. The electrodes were then implanted epidurally to evaluate the ability of each diameter to detect neural activity. Results show that their performance at low frequencies (up to 300 Hz) depends on the distance from the signal source rather than on the electrode diameter, while at high frequencies (above 200 Hz) small electrodes have higher background noises than large ones, unless they are coated with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS).

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Section: Resultsmentioning

confidence: 99%

Glassy Carbon Electrocorticography Electrodes on Ultra-Thin and Finger-Like Polyimide Substrate: Performance Evaluation Based on Different Electrode Diameters

et al. 2018

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“…This can be ascribed to the fact that i) below a certain low impedance value, the shunt loss is minimized regardless of the value of the coating impedance; ii) many factors, including the acute/chronic occurrence of the glial scar, affect the overall recorded signals following still poorly understood pathways, making hard to disentangle the contribution of the CP coating alone to the recorded signal. [ 62 , 73 , 229 ]…”

Section: Discussionmentioning

confidence: 99%

Poly(3,4‐ethylenedioxythiophene)‐Based Neural Interfaces for Recording and Stimulation: Fundamental Aspects and In Vivo Applications

et al. 2022

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Next‐generation neural interfaces for bidirectional communication with the central nervous system aim to achieve the intimate integration with the neural tissue with minimal neuroinflammatory response, high spatio‐temporal resolution, very high sensitivity, and readout stability. The design and manufacturing of devices for low power/low noise neural recording and safe and energy‐efficient stimulation that are, at the same time, conformable to the brain, with matched mechanical properties and biocompatibility, is a convergence area of research where neuroscientists, materials scientists, and nanotechnologists operate synergically. The biotic–abiotic neural interface, however, remains a formidable challenge that prompts for new materials platforms and innovation in device layouts. Conductive polymers (CP) are attractive materials to be interfaced with the neural tissue and to be used as sensing/stimulating electrodes because of their mixed ionic‐electronic conductivity, their low contact impedance, high charge storage capacitance, chemical versatility, and biocompatibility. This manuscript reviews the state‐of‐the‐art of poly(3,4‐ethylenedioxythiophene)‐based neural interfaces for extracellular recording and stimulation, focusing on those technological approaches that are successfully demonstrated in vivo. The aim is to highlight the most reliable and ready‐for‐clinical‐use solutions, in terms of materials technology and recording performance, other than spot major limitations and identify future trends in this field.

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“…One of the most desirable features in neural interface is their compliance to the mechanical properties of the host tissue. It is important that ECoG arrays conform to brain without the need of applying external forces, which is influenced by the flexibility as well as the footprint of the implanted structures. It has been shown that, despite a much‐reduced invasion compared to penetrating electrodes, ECoG devices do experience foreign‐body response and glial scar formation which ultimately leads to the encapsulation and subsequent loss of functionality of the implants.…”

Section: Resultsmentioning

confidence: 99%

“…In the recent years, electrocorticography (ECoG) electrodes have been established as compromise between invasiveness and spatial selectivity. When they are flexible and able to conform to curvilinear bodies, they allow for high amplitude recordings up to the resolution of spikes even if the Young's modulus of the device is orders of magnitude higher than the tissue underneath . Surface biocompatibility of the implant materials ensure intended interactions with the target cells …”

Section: Introductionmentioning

confidence: 99%

Flexible Bioelectronic Devices Based on Micropatterned Monolithic Carbon Fiber Mats

Vomero

Gueli

Zucchini

et al. 2019

Adv Materials Technologies

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Polymer‐derived carbon can serve as an electrode material in multimodal neural stimulation, recording, and neurotransmitter sensing platforms. The primary challenge in its applicability in implantable, flexible neural devices is its characteristic mechanical hardness that renders it difficult to fabricate the entire device using only carbon. A microfabrication technique is introduced for patterning flexible, cloth‐like, polymer‐derived carbon fiber (CF) mats embedded in polyimide (PI), via selective reactive ion etching. This scalable, monolithic manufacturing method eliminates any joints or metal interconnects and creates electrocorticography electrode arrays based on a single CF mat. The batch‐fabricated CF/PI composite structures, with critical dimension of 12.5 µm, are tested for their mechanical, electrical, and electrochemical stability, as well as to chemicals that mimic acute postsurgery inflammatory reactions. Their recording performance is validated in rat models. Reported CF patterning process can benefit various carbon microdevices that are expected to feature flexibility, material stability, and biocompatibility.

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Achieving Ultra-Conformability With Polyimide-Based ECoG Arrays

Cited by 11 publications

References 12 publications

Glassy Carbon Electrocorticography Electrodes on Ultra-Thin and Finger-Like Polyimide Substrate: Performance Evaluation Based on Different Electrode Diameters

Glassy Carbon Electrocorticography Electrodes on Ultra-Thin and Finger-Like Polyimide Substrate: Performance Evaluation Based on Different Electrode Diameters

Poly(3,4‐ethylenedioxythiophene)‐Based Neural Interfaces for Recording and Stimulation: Fundamental Aspects and In Vivo Applications

Flexible Bioelectronic Devices Based on Micropatterned Monolithic Carbon Fiber Mats

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