Fractal Microelectrodes for More Energy‐Efficient Cervical Vagus Nerve Stimulation

• Published in: Advanced healthcare materials Vol. 12; no. 19; pp. e2202619 - n/a
• Main Authors: Lim, Jongcheon, Eiber, Calvin D., Sun, Anina, Maples, Amanda, Powley, Terry L., Ward, Matthew P., Lee, Hyowon
• Format: Journal Article
• Language: English
• Published: Germany 01.07.2023
• Subjects: fractal; Fractals; Microelectrodes; Vagus Nerve - physiology; vagus nerve stimulation; Vagus Nerve Stimulation - methods; fractal; vagus nerve stimulation; microelectrodes
• ISSN: 2192-2640; 2192-2659
• DOI: 10.1002/adhm.202202619

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. Microelectrodes can be used to increase neurostimulation selectivity. However, smaller electrodes have higher impedance, which can affect neurostimulation efficiency. This study presents an in vivo evaluation of microelectrodes with circular or fractal geometries. The findings suggest that fractal microelectrodes consume 52% less energy than circular microelectrodes in activating unmyelinated C‐fibers in the vagus nerve with lowered activation threshold.