Hollow ring-like flexible electrode architecture enabling subcellular multi-directional neural interfacing

Implantable neural microelectrodes for recording and stimulating neural activity are critical for research in neuroscience and clinical neuroprosthetic applications. A current need exists for developing new technological solutions for obtaining highly selective and stealthy electrodes that provide reliable neural integration and maintain neuronal viability. This paper reports a novel Hollow Ring-like type electrode to sense and/or stimulate neural activity from three-dimensional neural networks. Due to its unique design, the ring electrode architecture enables easy and reliable access of the electrode to three-dimensional neural networks with reduced pressure on the biological tissue, while providing improved electrical interface with cells. The Hollow ring electrodes, particularly when coated with the conducting polymer PEDOT:PSS, show improved electrical properties with extremely low impedance and high charge injection capabilities, when compared to traditional planar disk-type electrodes. The ring design also serves as an optimal architecture for cell gowth to create an optimal subcellular electrical– neural interface. In addition, we demonstrated that the quality of recorded neural signals by the ring electrode was higher than recordings from a traditional disk-type electrode in terms of signal-to-noise ratio (SNR) and burst detection from 3D neuronal networks in vitro . Overall, our results suggest the great potential of the hollow ring design for developing next-generation microelectrodes for applications in neural interfaces used in physiological studies and neuromodulation applications. ### Competing Interest Statement The authors have declared no competing interest.