基于MEMS技术在截肢残端重建高分辨率人工触觉的机理研究

Dexterous manipulation of prosthetic hands cannot be achieved due to loss of finger tactile sensation for the upper-limb amputees. It was found by experiment that artificial tactile sensation can improve the amputees’ object grasp control while using prosthetic hands. However, at present, the spatial resolution of artificial tactile sensation is still not enough for the amputees to accomplish fine movement control, which limits the widespread acceptance of the prosthetic hands. It has been preliminarily confirmed that the evoked finger sensation (EFS) on the stump skin could be established for the upper-limb amputees with discrimination of different fingers and sensory modalities. It is assumed that artificial tactile sensation at various local areas within single EFS area will guide the amputees to restore more dexterous prosthetic finger manipulation. For this purpose, this project aims to do the following research work. 1) Modeling the novel three-dimensional TENS by incorporation of finite element method and double-layer-cable tactile fiber NEURON model to investigate the response mechanism of the subcutaneous sensory afferents, which will guide the optimization of the multichannel stimulating electrode array and stimulating current parameters; 2) Investigating the flexible thin-film multichannel electrode array with high-charge-transfer capability using MEMS techniques; 3) Evaluating the spatial resolution and sensation current threshold of tactile sensation at the EFS area by method of limits in psychophysics. This project will advance the fineness and practicability of artificial tactile sensation, and lay solid theoretical and experimental foundations for the clinical application of tactile sensory feedback associated with intelligent prosthetic hands.

上肢截肢患者因失去手指触觉而无法完成对假手的精细控制。实验发现人工触觉技术可改善截肢患者使用假手抓握物体的能力，但现有人工触觉的空间分辨率仍无法满足截肢患者对假手精细运动控制的需要，难以在临床上推广应用。我们前期采用经皮神经电刺激(TENS)在残肢端诱发出了截肢手指的感觉，结果证明截肢患者能够区分出不同手指和感觉模式。我们假设诱发出同一手指多个不同局部区域的人工触觉，将可能引导截肢患者恢复出更加精细的假手手指操作。为此目的，我们将1）建立TENS三维计算神经仿真模型，研究感觉传入纤维的响应模式，指导电极阵列和刺激电流参数设计；2）基于MEMS技术，研发多通道柔性薄膜人工触觉电极阵列；3）开展心理物理学实验，基于最小变化法测定截肢患者的感觉阈值，评估截肢残端人工触觉的空间分辨率。该项目将显著提高截肢患者人工触觉的精细度和实用性，为智能化肌电假手的触觉反馈的临床应用提供理论和实验基础。

上肢截肢给截肢患者的身体和心理健康都造成了很大的伤害。然而，目前国际上最先进的商用肌电假肢手仍然缺乏可靠的假肢手触觉反馈（人工触觉）。本课题紧密围绕提高人工触觉的空间分辨能力，进行了如下主要研究内容：1）建立经皮神经电刺激（transcutaneous electrical nerve stimulation, TENS）的三维计算神经仿真模型；2）用于TENS的多通道柔性薄膜刺激电极阵列及其心理物理学实验；3）验证诱发指感区TENS人工触觉的空间分辨能力；4）基于外周植入式碳纳米管线电极技术的人工感觉的客观评估。.本课题取得的重要结果及其关键数据主要分为三个方面：1）新型三维TENS模型的建立：我们首次提出并验证了皮下有髓鞘Aβ和无髓鞘C型感觉传入纤维的有源模型结构。皮下大直径有髓鞘Aβ纤维兴奋阈值低，在强电流刺激条件下直径小于4 微米的纤维数量急剧增加；当直径为3 mm的小刺激电极在中间，3个同样尺寸的回收电极均匀分布在周围，且与刺激电极的圆心距离均为6 mm时，C型纤维的阈值最高，并高于皮下触觉相关的Aβ传入纤维的兴奋阈值。此时，可以实现3 mm小电极只产生触觉，而不产生痛觉的目的。2）基于截肢患者心理物理学实验的幻指辨识：多个幻指感区同时电刺激时，辨识率逐渐降低。单个、两个以及四个幻指的辨识率分别为85.83% (chance level:25%), 67.67% (10%), and 46.44% (6.7%)。3）基于神经束内碳纳米管线电极的人工触觉：首次表明暴露长度为500微米的碳纳米管线电极神经束内电刺激具有单个或相邻两个脚趾的分辨能力。且电极暴露长度越短，其空间选择性越高。.本课题的研究成果对于实现不同种类神经纤维的选择性电刺激编码具有重要科学意义，为基于神经束内电刺激实现更自然的人工触觉提供了坚实的基础。同时，该研究对于实现智能假肢手以及感觉丧失的运动康复具有重要的指导意义。