An Implantable Multi-Layer Carbon Nanoelectrode Based on MPCVD and Atmospheric Plasma Jet, for Recording of Intracellular Oxygen and Neural Signals

This paper reports an implantable multi-layer carbon nanoelectrode (IMC-NE) developed through a three-step microwave plasma chemical vapor deposition (MPCVD) process and a two-step cold atmospheric plasma jet branch focusing (CAPJBF) process. The layers on the surface of IMC-NE from the inside out are Pt, graphene (GNE), graphite-like carbon (GLC) featuring a 3D nanowire structure, and diamond. The sensing layer and inner channel at the tip are precisely exposed. GNE and GLC enhance the conductivity and charge storage capacity of the nanoelectrode (NE). The IMC-NE exhibits heightened sensitivity to variations in dissolved O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> concentration at - 0.6 V, with a linear relationship of about <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$8.83\ \text{pA}/\mu \mathrm{M}$</tex>. Finally, real-time changes in intracellular action potential as well as fluctuations in current and corresponding O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> concentrations, are recorded within a brain slice. All results underscore the potential of IMC-NE in in-situ monitoring of intracellular O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> levels and neuronal spikes, which is crucial for early and accurate diagnosis of neurological disorders. This work represents a breakthrough in “small” MEMS processing technologies and “transducers for a small world” in the field of implantable neural interfaces.