Neural microprobe modelling and microfabrication for improved implantation and mechanical failure mitigation

McGlynn, Eve; Walton, Finlay; Das, Rupam; Heidari, Hadi

doi:10.1098/rsta.2021.0007

Cited by 8 publications

(4 citation statements)

References 39 publications

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“…Thus, the metal layer assembled on a soft polymer substrate undergoing the same deformation challenge would be prone to irreversible and catastrophic changes, such as fracture, delamination, or sliding [78]. Inevitably, in order to reduce the damage to neurons caused by neural electrode arrays during implantation, the demand for soft substrates has increased, and most of the neural electrode arrays were composed of soft polymer substrates with high-conductivity metal designed to be used with a 90 • bend [79]. However, the neural electrode array in this study achieved a wide range of bending radius without affecting the electrical properties even if the bending angle was over 90 • Our neural electrode array could not only achieve large-angle bending but also maintain the electrical properties after bending because of the 3D space (known as RDLs) of the subsequent metal layer produced on the substrate by laser grooving.…”

Section: Electric Performance Of the Neural Electrode Array Under Ben...mentioning

confidence: 99%

Proof of Concept for Sustainable Manufacturing of Neural Electrode Array for In Vivo Recording

Tseng

Chen

et al. 2023

Biosensors

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Increasing requirements for neural implantation are helping to expand our understanding of nervous systems and generate new developmental approaches. It is thanks to advanced semiconductor technologies that we can achieve the high-density complementary metal-oxide-semiconductor electrode array for the improvement of the quantity and quality of neural recordings. Although the microfabricated neural implantable device holds much promise in the biosensing field, there are some significant technological challenges. The most advanced neural implantable device relies on complex semiconductor manufacturing processes, which are required for the use of expensive masks and specific clean room facilities. In addition, these processes based on a conventional photolithography technique are suitable for mass production, which is not applicable for custom-made manufacturing in response to individual experimental requirements. The microfabricated complexity of the implantable neural device is increasing, as is the associated energy consumption, and corresponding emissions of carbon dioxide and other greenhouse gases, resulting in environmental deterioration. Herein, we developed a fabless fabricated process for a neural electrode array that was simple, fast, sustainable, and customizable. An effective strategy to produce conductive patterns as the redistribution layers (RDLs) includes implementing microelectrodes, traces, and bonding pads onto the polyimide (PI) substrate by laser micromachining techniques combined with the drop coating of the silver glue to stack the laser grooving lines. The process of electroplating platinum on the RDLs was performed to increase corresponding conductivity. Sequentially, Parylene C was deposited onto the PI substrate to form the insulation layer for the protection of inner RDLs. Following the deposition of Parylene C, the via holes over microelectrodes and the corresponding probe shape of the neural electrode array was also etched by laser micromachining. To increase the neural recording capability, three-dimensional microelectrodes with a high surface area were formed by electroplating gold. Our eco-electrode array showed reliable electrical characteristics of impedance under harsh cyclic bending conditions of over 90 degrees. For in vivo application, our flexible neural electrode array demonstrated more stable and higher neural recording quality and better biocompatibility as well during the 2-week implantation compared with those of the silicon-based neural electrode array. In this study, our proposed eco-manufacturing process for fabricating the neural electrode array reduced 63 times of carbon emissions compared to the traditional semiconductor manufacturing process and provided freedom in the customized design of the implantable electronic devices as well.

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Section: Electric Performance Of the Neural Electrode Array Under Ben...mentioning

confidence: 99%

Proof of Concept for Sustainable Manufacturing of Neural Electrode Array for In Vivo Recording

Tseng

Chen

et al. 2023

Biosensors

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“…Neural microprobes contribute significantly to the study of brain function, brain diseases, and brain-machine interfaces (Li et al 2023 ; McGlynn et al 2022 ; Ward et al 2022 ). An intracortical microprobe needs to be implanted deep within the brain to directly interface with specific brain regions allowing for high-accuracy brain recording and stimulation (Atkinson et al 2021 ; Zhou et al 2023 ).…”

Section: Introductionmentioning

confidence: 99%

A self-stiffening compliant intracortical microprobe

Sharafkhani,

Long,

Adams

et al. 2024

Biomed Microdevices

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Utilising a flexible intracortical microprobe to record/stimulate neurons minimises the incompatibility between the implanted microprobe and the brain, reducing tissue damage due to the brain micromotion. Applying bio-dissolvable coating materials temporarily makes a flexible microprobe stiff to tolerate the penetration force during insertion. However, the inability to adjust the dissolving time after the microprobe contact with the cerebrospinal fluid may lead to inaccuracy in the microprobe positioning. Furthermore, since the dissolving process is irreversible, any subsequent positioning error cannot be corrected by re-stiffening the microprobe. The purpose of this study is to propose an intracortical microprobe that incorporates two compressible structures to make the microprobe both adaptive to the brain during operation and stiff during insertion. Applying a compressive force by an inserter compresses the two compressible structures completely, resulting in increasing the equivalent elastic modulus. Thus, instant switching between stiff and soft modes can be accomplished as many times as necessary to ensure high-accuracy positioning while causing minimal tissue damage. The equivalent elastic modulus of the microprobe during operation is ≈ 23 kPa, which is ≈ 42% less than the existing counterpart, resulting in ≈ 46% less maximum strain generated on the surrounding tissue under brain longitudinal motion. The self-stiffening microprobe and surrounding neural tissue are simulated during insertion and operation to confirm the efficiency of the design. Two-photon polymerisation technology is utilised to 3D print the proposed microprobe, which is experimentally validated and inserted into a lamb’s brain without buckling.

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“…Neural microprobes contribute signi cantly to the study of brain function, brain diseases, and brainmachine interfaces (Li, Wang & Fang 2023;McGlynn et al 2022;Ward et al 2022). An intracortical microprobe needs to be implanted deep within the brain to directly interface with speci c brain regions allowing for high-accuracy brain recording and stimulation (Atkinson et al 2021;Zhou et al 2023).…”

Section: Introductionmentioning

confidence: 99%

An Intracortical Microprobe with Adaptive Stiffness

Sharafkhani,

Long,

Adams

et al. 2023

Preprint

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Utilising a flexible intracortical microprobe to record/stimulate neurons minimises the incompatibility between the implanted microprobe and the brain, reducing tissue damage due to the brain micromotion. Applying bio-dissolvable coating materials temporarily makes a flexible microprobe stiff to tolerate the penetration force during insertion. However, the inability to adjust the dissolving time after the microprobe contact with the cerebrospinal fluid may lead to inaccuracy in the microprobe positioning. Furthermore, since the dissolving process is irreversible, any subsequent positioning error cannot be corrected by re-stiffening the microprobe. This study proposes a compliant intracortical microprobe whose equivalent elastic modulus increases because of the axial force applied by an inserter. Thus, instant switching between stiff and soft modes can be accomplished as many times as necessary to ensure high-accuracy positioning while causing minimal tissue damage. The equivalent elastic modulus of the microprobe during operation is ≈ 23 kPa, which is ≈ 42% less than the existing counterpart, resulting in ≈ 46% less maximum strain generated on the surrounding tissue under brain longitudinal motion. The microprobe with adaptive stiffness and surrounding neural tissue are simulated during insertion and operation to confirm the efficiency of the design. Two-photon polymerisation technology is utilised to 3D print the proposed microprobe, which is inserted into a lamb’s brain without buckling.

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Neural microprobe modelling and microfabrication for improved implantation and mechanical failure mitigation

Cited by 8 publications

References 39 publications

Proof of Concept for Sustainable Manufacturing of Neural Electrode Array for In Vivo Recording

Proof of Concept for Sustainable Manufacturing of Neural Electrode Array for In Vivo Recording

A self-stiffening compliant intracortical microprobe

An Intracortical Microprobe with Adaptive Stiffness

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