Keywords: soft neural microelectrode, MXene fiber, neural stimulation and recording, neural interface, brain-machine interface, neurotransmitters
Summary:The development of soft neural interfaces opens opportunities for long-term studying and modulating of brain functions and diseases with fewer side effects by minimizing the mechanical mismatch between artificial devices and soft tissues. However, few designs have enabled both electrical and chemical sensing – necessary for capturing the diverse neural signals in vivo – as simultaneous high electrical conductivity and redox surfaces are required for such multifunctional electrodes. Here we report a novel method leveraging the unique combinations of electrical conductivity, functional surfaces, and solution processibility of MXenes, an emerging class of 2D nanomaterials, to produce a thin conformal MXene coating on nylon filaments (30-300 µm in diameter) at a fast speed (up to 15 mm/s). The MXene electrodes are subsequently encapsulated with parylene C, allowing only the tip of the electrode to be exposed, for a cellular-level detection and simulation of neurons. The highly aligned MXene coatings provide the microelectrodes with an electrical impedance as low as 2kΩ at 1kHz and a large charge injection capacity despite of a small MXene exposure at the tip. In addition, the gaps between MXene flakes act as vertical channels providing fast analyte access to ample redox surfaces during the detection of neural transmitters. These versatile MXene filament microelectrodes offer a robust, miniaturized platform for the monitoring and stimulation of neural activities, facilitating a greater understanding of health and disease.