Improving the stability of electrode arrays

Cover article of Advanced Biosystems on the development of innovative adhesion promoters for enhanced stability in thin-film glassy carbon ECoG arrays



Credits to M. Vomero, Dr D. Ricci, M. Cruz, V. Faria

In the world of neural implants, one of the main challenges is to build electrically functional devices that can interface the nervous system without harming it or getting harmed. The interaction between natural and artificial is more complex than it sounds and its success is based on the molecular-level equilibrium of fundamentally different systems. Chemical and mechanical coexistence of different materials in an implant finds limitations, especially in the long term, when it is immersed into a humid, warm and saline environment like the human body. The risk of deterioration, delamination and corrosion - with eventual loss of functionality - is very high and can lead to the injury of the host tissue by solid particles or leaching agents.

One solution is to use inter-layer adhesion promoters that achieve strong bond formation between chemically and physically dissimilar materials. Depending on the application and the target specifications, in fact, the components of an implant can be made from different materials. Carbon is well known for biosensing neurotransmitters and for electrical stimulation, and it has been gaining popularity in the field of neural engineering. However, flexible electrodes arrays on polymeric substrates with integrated metal tracks and glass-like carbon electrodes have many interfaces prone to long-term failure due to material delamination.

In their Advanced Biosystems paper, Maria Vomero et al. investigate whether the integration of adhesion promoters (e.g. silicon carbide and diamond-like carbon) into flexible thin-film carbon neural devices can create strong and humidity-resistant interfaces and result in stable and non-delaminating implants. They test the stability of their advanced electrode-technology with a variety of experiments, in vitro and in vivo, and find no signs of delamination or failure on the manufactured devices. This study shows how, in a detail-oriented manner, it is possible to create a functional and stable system made with a diversity of components blended together with the use of ad-hoc interlayers.

Open access to the original article can be found here.


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