Flexible Electrode for Implantable Neural Devices

Tsang, W.M.; Je, Minkyu

doi:10.1007/978-1-4614-8151-5_6

Cited by 5 publications

(4 citation statements)

References 210 publications

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“…One of the first intracortical electrode designs in use was the metal wire electrode. Its use dates back to 1950 ([ 1 ], p. 122). Several examples can be found in [ 2 , 3 ].…”

Section: Introductionmentioning

confidence: 99%

Failure Reason of PI Test Samples of Neural Implants

Guljakow

Lang

2023

Sensors

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Samples that were meant to simulate the behavior of neural implants were put into Ringer’s solution, and the occurring damage was assessed. The samples consist of an interdigitated gold-structure and two contact pads embedded between two Polyimide layers, resulting in free-floating structures. The two parts of the interdigitated structure have no electric contacts and are submerged in the solution during the experiment. The samples were held at temperatures of 37 and 57 ∘C in order to undergo an accelerated lifetime test and to compare the results. During the course of the experiment, a voltage was applied and measured over a resistance of 1 kOhm over time. Arduinos were used as measuring devices. As the intact samples are insulating, a sudden rise in voltage indicates a sample failure due to liquid leaking in between the two polyimide layers. Once a short-circuit occurred and a sample broke down, the samples were taken out of the vial and examined under a microscope. In virtually all cases, delamination was observable, with variation in the extent of the delaminated area. A comparison between measured voltages after failure and damage did not show a correlation between voltage and area affected by delamination. However, at a temperature of 37 ∘C, voltage remained constant most of the time after delamination, and a pin-hole lead to a lower measured voltage and strong fluctuations. Visually, no difference in damage between the 37 and the 57 ∘C samples was observed, although fluctuations of measured voltage occurred in numerous samples at a higher temperature. This difference hints at differences in the reasons for failure and thus limited applicability of accelerated lifetime tests.

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“…One of the first intracortical electrode designs in use was the metal wire electrode. Its use dates back to 1950 ([ 1 ], p. 122). Several examples can be found in [ 2 , 3 ].…”

Section: Introductionmentioning

confidence: 99%

Failure Reason of PI Test Samples of Neural Implants

Guljakow

Lang

2023

Sensors

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“…It is either a layer of chromium having a thickness of several tens of nm, [1][2][3][4][5][6] (p. 42) or titanium [7][8][9][10] (p. 126f) [11][12][13], or titanium-oxide [14] (p. 43ff) that are deposited onto polymers, such as PPX-C, SU-8, polyimide, etc. For neural implants, an overall metal-layer thickness between 200 and 300 nm is often reported with various examples ranging from 10/200 Ti/Au [15] to 15/270 TiOx/Pt [14] (p. 47), and several other in between, e.g., 20/200 Ti/Au [8] 20/250 Cr/Au [1,3,9,10,16]. Several neural implants or test structures had a gold-layer thickness of 300 nm [4,[17][18][19].…”

Section: Introduction 1neural Implantsmentioning

confidence: 99%

“…Practical examples of gold deposited on polyimide, where an adhesive layer of titanium was used can be found for electrocorticography (ECoG) in [17], and for intracortical sensors [21]. Usual methods for the deposition of such layers are thermal evaporation [8] or e-beam evaporation [1,3,10,15]. Another approach is to modify the surface chemistry of polymers to facilitate the adhesion of gold, as can be seen in [22], to cure the polymer after the deposition of gold [23], make a pre-treatment with an oxygen-plasma [24] or no treatment at all [25].…”

Section: Introduction 1neural Implantsmentioning

confidence: 99%

Adhesion of HIPIMS-Deposited Gold to a Polyimide Substrate

Guljakow

Lang

2023

Coatings

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Gold is the preferred material for conductive structures in neural implants. The hitherto employed process applies adhesive layers to avoid delamination of gold structures from a polymeric substrate. The possibility to deposit gold without the use of adhesive layers is offered by the high-power impulse magnetron sputtering (HIPIMS) process. In this work, it is shown that it is possible to utilize the HIPIMS process to deposit gold onto polyimide while having enough adhesion between these two layers to omit the use of an adhesive layer. A scratch test was performed to demonstrate the adherence between the layers.

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“…However, microwires deform upon insertion [29], cause tissue damage, and can deviate from their initial target [19], [29]- [31]. Commercial microwires have caused moderate inflammation and encapsulation, degrading the electrode [6], [32], [33]. The microwires may also corrode in vivo, causing cracks in the insulation and electrode sites [30].…”

Section: Introductionmentioning

confidence: 99%

Benchtop Carbon Fiber Microelectrode Array Fabrication Toolkit

Patel

Welle

et al. 2021

Preprint

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Background: Conventional neural probes are primarily fabricated in a cleanroom, requiring the use of multiple expensive and highly specialized tools. New method: We propose a cleanroom 'light' fabrication process of carbon fiber neural electrode arrays that can be learned quickly by an inexperienced cleanroom user. This carbon fiber electrode array fabrication process requires just one cleanroom tool, a parylene-c deposition machine, that can be learned quickly or outsourced to a commercial processing facility at marginal cost. Our fabrication process also includes hand-populating printed circuit boards, insulation, and tip optimization. Results: The three different tip optimizations explored here (Nd:YAG laser, blowtorch, and UV laser) result in a range of tip geometries and 1kHz impedances, with blowtorched fibers resulting in the lowest impedance. While previous experiments have proven laser and blowtorch electrode efficacy, this paper also shows UV laser cut fibers can record neural signals in vivo. Comparison with existing methods: Existing carbon fiber arrays either do not have individuated electrodes in favor of bundles or require cleanroom fabricated guides for population and insulation. The proposed arrays use only tools that can be used at a benchtop for fiber population. Conclusions: This carbon fiber electrode array fabrication process allows for quick customization of bulk array fabrication at a reduced price compared to commercially available probes.

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Flexible Electrode for Implantable Neural Devices

Cited by 5 publications

References 210 publications

Failure Reason of PI Test Samples of Neural Implants

Failure Reason of PI Test Samples of Neural Implants

Adhesion of HIPIMS-Deposited Gold to a Polyimide Substrate

Benchtop Carbon Fiber Microelectrode Array Fabrication Toolkit

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