TNSRE presents

# Sharpened and mechanically durable carbon fiber electrode arrays for neural recording

Bioelectric medicine treatments target disorders of the nervous system unresponsive to pharmacological methods. While current stimulation paradigms effectively treat many disorders, the underlying mechanisms are relatively unknown, and current neuroscience recording electrodes are often limited in their specificity to gross averages across many neurons or axons. Here, we develop a novel, durable carbon fiber electrode array adaptable to many neural structures for precise neural recording. Carbon fibers ( $6.8~\mu \text{m}$ diameter) were sharpened using a reproducible blowtorchmethod that uses the reflection of fibers against the surface of a water bath. The arrays were developed by partially embedding carbon fibers in medical-grade silicone to improve durability. We recorded acute spontaneous electrophysiology from the rat cervical vagus nerve (CVN), feline dorsal root ganglia (DRG), and rat brain. Blowtorching resulted in fibers of 72.3 ± 33.5-degree tip angle with $146.8~\pm ~17.7~\mu \text{m}$ exposed carbon. Observable neural clusters were recorded using sharpened carbon fiber electrodes fromrat CVN ( $41.8~\mu \text{V}_{\text {pp}}$ ), feline DRG ( $101.1~\mu \text{V}_{\text {pp}}$ ), and rat brain ( $80.7~\mu \text{V}_{\text {pp}}$ ). Recordings from the feline DRG included physiologically relevant signals from increased bladder pressure and cutaneous brushing. These results suggest that this carbon fiber array is a uniquely durable and adaptable neural recordingdevice. In the future, this device may be useful as a bioelectric medicine tool for diagnosis and closed-loop neural control of therapeutic treatments and monitoring systems.