School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
Graduate School of Biomedical Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia.
Comput Biol Med. 2024 Jun;176:108556. doi: 10.1016/j.compbiomed.2024.108556. Epub 2024 May 9.
Carbon nanotube (CNT) fiber electrodes have demonstrated exceptional spatial selectivity and sustained reliability in the context of intrafascicular electrical stimulation, as evidenced through rigorous animal experimentation. A significant presence of unmyelinated C fibers, known to induce uncomfortable somatosensory experiences, exists within peripheral nerves. This presence poses a considerable challenge to the excitation of myelinated Aβ fibers, which are crucial for tactile sensation. To achieve nuanced tactile sensory feedback utilizing CNT fiber electrodes, the selective stimulation of Aβ sensory afferents emerges as a critical factor. In confronting this challenge, the present investigation sought to refine and apply a rat sciatic-nerve model leveraging the capabilities of the COMSOL-NEURON framework. This approach enables a systematic evaluation of the influence exerted by stimulation parameters and electrode geometry on the activation dynamics of both myelinated Aβ and unmyelinated C fibers. The findings advocate for the utilization of current pulses featuring a pulse width of 600 μs, alongside the deployment of CNT fibers characterized by a diminutive diameter of 10 μm, with an exclusively exposed cross-sectional area, to facilitate reduced activation current thresholds. Comparative analysis under monopolar and bipolar electrical stimulation conditions revealed proximate activation thresholds, albeit with bipolar stimulation exhibiting superior fiber selectivity relative to its monopolar counterpart. Concerning pulse waveform characteristics, the adoption of an anodic-first biphasic stimulation modality is favored, taking into account the dual criteria of activation threshold and fiber selectivity optimization. Consequently, this investigation furnishes an efficacious stimulation paradigm for the selective activation of touch-related nerve fibers, alongside provisioning a comprehensive theoretical foundation for the realization of natural tactile feedback within the domain of prosthetic hand applications.
碳纳米管 (CNT) 纤维电极在神经内电刺激方面表现出了出色的空间选择性和持续可靠性，这在严格的动物实验中得到了证明。周围神经中存在大量未髓鞘化的 C 纤维，已知这些纤维会引起不舒服的感觉。这对髓鞘化的 Aβ纤维的兴奋构成了相当大的挑战，因为 Aβ纤维对触觉至关重要。为了利用 CNT 纤维电极实现精细的触觉感觉反馈，选择性刺激 Aβ感觉传入纤维成为一个关键因素。在应对这一挑战时，本研究旨在利用 COMSOL-NEURON 框架的能力，改进和应用大鼠坐骨神经模型。这种方法可以系统地评估刺激参数和电极几何形状对髓鞘化的 Aβ和未髓鞘化的 C 纤维激活动力学的影响。研究结果表明，应使用脉冲宽度为 600 μs 的电流脉冲，并使用直径为 10 μm 的 CNT 纤维，其横截面仅暴露在外，以降低激活电流阈值。单极和双极电刺激条件下的比较分析表明，激活阈值相近，尽管双极刺激相对于单极刺激具有更好的纤维选择性。关于脉冲波形特征，应采用阳极先的双相刺激模式，这是考虑到激活阈值和纤维选择性优化的双重标准。因此，本研究为选择性激活与触摸相关的神经纤维提供了一种有效的刺激范式，并为在假肢手应用领域实现自然触觉反馈提供了全面的理论基础。
