Wang Yuheng, Lin Junjie, Zhu Kai, Nie Yuhui, Wang Mengyuan, Ma Xiaoxu, Liu Xu, Wang Ruru, Mai Wenshu, Chu Fangxuan, Liu Ruixu, Wu Jiankang, Jin Jingna, Zhou Xiaoqing, Ma Ren, Wang Xin, Yin Tao, Liu Zhipeng, Zhang Shunqi
Institute of Biomedical Engineering, Chinese Academy of Medical Science & Peking Union Medical College, Tianjin, 300192, China.
Tianjin Key Laboratory of Neuroregulation and Neurorepair, Tianjin, 300192, China.
J Neuroeng Rehabil. 2025 Apr 7;22(1):76. doi: 10.1186/s12984-025-01575-2.
Electromagnetic field-based neuroregulation technology is a crucial technique for treating central nervous system and peripheral nervous system disorders. However, the use of invasive electrodes has unavoidable problems such as the risk of inflammation due to high hardness, electrical connections and the need for batteries. On the other hand, non-invasive magnetic stimulation has limitations such as centimeter-level focal areas and shallow stimulation depth.
To enhance the precision and effectiveness of wireless magnetic stimulation, we employed a figure-8 magnetic stimulation coil (8-coil) to generate a magnetic field, combined with an injectable, highly conductive, and flexible liquid metal (LM) to produce a millimeter-scale focused electric field. A coaxial electric field measurement electrode was used to establish an agar phantom-based electric field measurement platform. The sciatic nerve of C57 mice was stimulated under acute anesthesia conditions, and electromyography (EMG) signals were collected to evaluate the enhancement of stimulation effects. Long-term safety was assessed through four weeks of implantation.
Theoretical analysis and finite element simulations demonstrated that the combination of LM and the 8-coil generated a millimeter-scale enhanced vector electric field within the tissue. Measured electric field distributions closely aligned with theoretical and simulation results. In the sciatic nerve experiments on mice, 1 µL of LM under a 0.45 T magnetic field significantly increased EMG signals and leg movement amplitude by approximately 500%. Long-term implantation under magnetic stimulation revealed no adverse effects.
This method utilizes focused electric fields to improve the precision and effectiveness of neuro-magnetic stimulation. It holds promise as a novel approach for precise stimulation. Preliminary evidence was provided for the safety of in vivo LM implantation under external magnetic fields.
基于电磁场的神经调节技术是治疗中枢神经系统和周围神经系统疾病的关键技术。然而，侵入性电极的使用存在不可避免的问题，如硬度高导致的炎症风险、电连接以及对电池的需求。另一方面，非侵入性磁刺激存在诸如厘米级聚焦区域和浅刺激深度等局限性。
为提高无线磁刺激的精度和有效性，我们采用一个8字形磁刺激线圈（8线圈）来产生磁场，并结合可注射的、高导电性且灵活的液态金属（LM）以产生毫米级聚焦电场。使用同轴电场测量电极建立基于琼脂模型的电场测量平台。在急性麻醉条件下刺激C57小鼠的坐骨神经，并收集肌电图（EMG）信号以评估刺激效果的增强情况。通过四周的植入来评估长期安全性。
理论分析和有限元模拟表明，LM与8线圈的组合在组织内产生了毫米级增强矢量电场。测量的电场分布与理论和模拟结果紧密吻合。在小鼠坐骨神经实验中，在0.45 T磁场下1 μL的LM显著增加了EMG信号以及腿部运动幅度，增幅约为500%。磁刺激下的长期植入未显示出不良影响。
该方法利用聚焦电场提高了神经磁刺激的精度和有效性。它有望成为一种精确刺激的新方法。为外部磁场下体内LM植入的安全性提供了初步证据。
