Browsing by Author "Lim, Jongcheon"

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    Fractal Microelectrodes for More Energy-Efficient Cervical Vagus Nerve Stimulation
    (Wiley, 2023) Lim, Jongcheon; Eiber, Calvin D.; Sun, Anina; Maples, Amanda; Powley, Terry L.; Ward, Matthew P.; Lee, Hyowon; Medicine, School of Medicine
    Vagus nerve stimulation (VNS) has the potential to treat various peripheral dysfunctions, but the traditional cuff electrodes for VNS are susceptible to off-target effects. Microelectrodes may enable highly selective VNS that can mitigate off-target effects, but they suffer from the increased impedance. Recent studies on microelectrodes with non-Euclidean geometries have reported higher energy efficiency in neural stimulation applications. These previous studies use electrodes with mm/cm-scale dimensions, mostly targeted for myelinated fibers. This study evaluates fractal microelectrodes for VNS in a rodent model (N = 3). A thin-film device with fractal and circle microelectrodes is fabricated to compare their neural stimulation performance on the same radial coordinate of the nerve. The results show that fractal microelectrodes can activate C-fibers with up to 52% less energy (p = 0.012) compared to circle microelectrodes. To the best of the knowledge, this work is the first to demonstrate a geometric advantage of fractal microelectrodes for VNS in vivo.
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    Hydrogel Adhesive Integrated‐Microstructured Electrodes for Cuff‐Free, Less‐Invasive, and Stable Interface for Vagus Nerve Stimulation
    (Wiley, 2025) Park, Jae Young; Lim, Jongcheon; Russell, Carl R., III; Chen, Pei-Lun; Eksioglu, Deniz; Hong, Seokkyoon; Mesa, Juan C.; Ward, Matthew P.; Lee, Chi Hwan; Lee, Hyowon; Medicine, School of Medicine
    Vagus nerve stimulation (VNS) is a recognized treatment for neurological disorders, yet the surgical procedure carries significant risks. During the process of isolating or cuffing the vagus nerve, there is a danger of damaging the nerve itself or the adjacent carotid artery or jugular vein. To minimize this risk, here we introduce a novel hydrogel adhesive-integrated and stretchable microdevice that provides a less invasive, cuff-free option for interfacing with the vagus nerve. The device features a novel hydrogel adhesive formulation that enables crosslinking on biological tissue. The inclusion of kirigami structures within the thin-film microdevice creates space for uniform hydrogel-to-epineurium contact while accommodating the stiffness changes of the hydrogel upon hydration. Using a rodent model, we demonstrate a robust device adhesion on a partially exposed vagus nerve in physiological fluid even without the vagus nerve isolation and cuffing process. Our device elicted stable and clear evoked compound action potential (~1500 µV peak-to-peak) in C-fibers with a current amplitude of 0.4 mA. We believe this innovative platform provides a novel, less-risky approach to interface with fragile nerve and vascular structures during VNS implantation.