BME PhD Final Defense Announcement for Jongcheon Lim (H. Lee, advisor) Everyone is invited to attend the public presentation beginning at 3:00 PM. Title: Toward Advanced Neural Interfaces for Selective Vagus Nerve Stimulation Date: June 1, 2023 Time: 3:00 PM Location: MJIS 2001 and Zoom - https://purdue-edu.zoom.us/j/95239025355?pwd=Z2xDOEJ5K3ZKcUdwNXNldTVLNVBNUT0... Thesis Committee: Hyowon Lee, Chair; Chi Hwan Lee; Edward Bartlett; Matthew P. Ward 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 enables more advanced neural interfaces, current devices for electrical neuromodulation rely on relatively bulky system such as helical cuff electrode for VNS, which stimulates entire fascicle indiscriminately. In this presentation, we show three approaches towards selective vagus nerve stimulation (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 stretchable neural interface and applied a tissue-adhesive hydrogel to enable tough adhesion of the cuff electrode, which can be potentially used to fix the position of microelectrode for a reliable selective stimulation with minimal mechanical mismatch. Lastly, we developed a microchannel electrode array device to potentially measure high-quality of single fiber action potential (SFAP) from the abdominal vagal trunk of rat to explore natural patterns selective organ activities which can be used for a fine-tuned selective VNS. Our 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.