First long term in vivo study on subdurally implanted Micro-ECoG electrodes, manufactured with a novel laser technology

Abstract

A novel computer aided manufacturing (CAM) method for electrocorticography (ECoG) microelectrodes was developed to be able to manufacture small, high density microelectrode arrays based on laser-structuring medical grade silicone rubber and high purity platinum. With this manufacturing process, we plan to target clinical applications, such as presurgical epilepsy monitoring, functional imaging during cerebral tumor resections and brain-computer interface control in paralysed patients, in the near future. This paper describes the manufacturing, implantation and long-term behaviour of such an electrode array. In detail, we implanted 8-channel electrode arrays subdurally over rat cerebral cortex over a period of up to 25 weeks. Our primary objective was to ascertain the electrode's stability over time, and to analyse the host response in vivo. For this purpose, impedance measurements were carried out at regular intervals over the first 18 weeks of the implantation period. The impedances changed between day 4 and day 7 after implantation, and then remained stable until the end of the implantation period, in accordance with typical behaviour of chronically implanted microelectrodes. A post-mortem histological examination was made to assess the tissue reaction due to the implantation. A mild, chronically granulated inflammation was found in the area of the implant, which was essentially restricted to the leptomeninges. Overall, these findings suggest that the concept of the presented ECoG-electrodes is promising for use in long-term implantations.

Graphene-based carbon-layered electrode array technology for neural imaging and optogenetic applications

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Graphitic Carbon Electrodes on Flexible Substrate for Neural Applications Entirely Fabricated Using Infrared Nanosecond Laser Technology

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“…In the field of neural prostheses, much attention is now given to the long-term performance of the materials directly interfacing with the nervous system 1–6 . Neural interfaces indeed play a critical role in chronic applications, where they have to outlast the highly humid and oxidative body environment without undergoing delamination or corrosion and thus losing their functionality over time 7–13 .…”

In Vitro and In Vivo Long-term Electrochemical Properties of Electrodes with Femtosecond-laser-induced Porosity for Visual Prostheses Based on Suprachoroidal Transretinal Stimulation

“…(24) As the high-frequency component of the impedance bypasses the electric double layer capacity, its value reflects R sol . (25) The primary reason the high-frequency component of the electrode impedance increases over time is considered to be the encapsulation of the electrode by connective tissues. The increase in solution resistance is not involved in the electrochemical reaction and is related to the potential of the current source.…”