BME PhD Preliminary Exam Announcement for Jongcheon Lim (H. Lee and M. Ward, co-advisors) Everyone is invited to attend the public presentation beginning at 9:30 AM EST. Title: Toward advanced neural interfaces for selective vagus nerve stimulation Date: July 28, 2022 Time: 9:30 AM EST Location: MJIS 2001 Thesis Committee members: Dr. Hyowon Lee (major professor), Dr. Mathew Ward (co-advisor), Dr. Chi-Hwan Lee, Dr. Edward Bartlett Abstract: Vagus nerve branches to multiple organs such as heart, stomach, and spleen to regulate their physiological activities. Selective activation of a portion of fibers in the vagus nerve can potentially modulate specific organ activities without off-target effect. Despite recent advancements in microfabrication technology that enable more advanced neural interfaces, current devices for vagus nerve stimulation (VNS) rely on relatively bulky system such as helical cuff electrode, which stimulates entire fascicle indiscriminately. In this presentation, we show three approaches towards selective VNS. First, we investigated VNS using microelectrode with circle and Vicsek fractal shape. Our rat study shows that fractal microelectrode can activate C-fibers in cervical vagus nerve with higher energy efficiency compared to circle microelectrode. Secondly, we developed stretchable and adhesive cuff device for a compliant neural interface for a long-term stability. We designed Y-shaped kirigami thin-film device for stretchability and applied a tissue-adhesive hydrogel to enable tough adhesion of the cuff electrode to the nerve, which can be potentially used to fix the position of microelectrode for a reliable selective stimulation with minimal mechanical mismatch. We plan to test the device in rat model to evaluate the efficacy of the stimulation and potential failure modes. Lastly, we developed a microchannel electrode array device to measure high-quality of single fiber action potential (SFAP) from the teased fibers in abdominal vagal trunk of rat to explore natural patterns selective organ activities which can be used for a fine-tuned selective VNS. Our preliminary results show the potential of measuring C-fiber activities evoked by cervical VNS. In the future, we plan to apply an improved design to increase signal to noise ratio to capture the spontaneous SFAP from the teased nerve fibers.