目的 针对传统水凝胶电极在长时表面肌电（sEMG）监测中因溶胀导致的界面接触失稳与信号失真问题,制备了一种聚电解质增强型抗溶胀柔性电极并构建了肌肉疲劳监测系统。方法 采用聚乙烯醇（PVA）与明胶（Gelatin）构建物理骨架,引入[2-(丙烯酰氧基)乙基]三甲基氯化铵（AETMAC）与聚丙烯酸钠（PAAS）形成离子导电网络,利用PAAS的渗透压机制抑制溶胀;通过部分还原氧化石墨烯（p-rGO）与单宁酸（TA）进行表面功能化改性,以提升材料的导电性与界面黏附力。基于该电极构建了针对疲劳特征频段（20~150 Hz）的采集终端,联合时频域特征评估肌肉疲劳。结果 实验表明,该电极离子电导率达1.54 S/m,皮肤黏附力为11.36 kPa;在生理盐水中浸泡160 h后的平衡溶胀率仅为4.36%,表现出优异的湿环境稳定性。监测系统在450 Hz采样率下实现了约36 dB信噪比的高保真信号采集,并成功捕捉到疲劳引起的中值频率由64.2 Hz向58.3 Hz的漂移。结论 该电极有效解决了传统湿电极在湿环境下易溶胀和界面失稳的问题,结合所构建的系统实现了肌肉疲劳的精确量化评估,在可穿戴健康监测及人机交互界面领域具有应用价值。
Abstract
Stable bioelectronic interfaces are essential for high-quality surface electromyography (sEMG) monitoring, especially under long-term wearing, sweating, and humid or aqueous conditions. Conventional Ag/AgCl gel electrodes can provide acceptable signal quality in short-term tests, but the drying of the conductive gel, unstable interfacial contact, and limited mechanical compliance often lead to impedance drift and motion artifacts during prolonged use. Conductive hydrogels have attracted increasing attention as soft electrode materials because of their tissue-like mechanical properties and intrinsic ionic conductivity. However, many hydrogel electrodes still suffer from excessive swelling in electrolyte-rich environments, which changes the electrode geometry and contact area and consequently deteriorates signal reproducibility. In this work, a polyelectrolyte-enhanced anti-swelling hydrogel electrode was developed for stable sEMG acquisition and muscle fatigue assessment. The hydrogel was constructed with polyvinyl alcohol (PVA) and gelatin as the physically crosslinked skeleton, while sodium polyacrylate (PAAS) and [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETMAC) were introduced to form an ionically conductive polyelectrolyte network. The charged polymer chains provided abundant mobile counterions and continuous ion-transport pathways, while the osmotic regulation associated with PAAS effectively restricted excessive water invasion in physiological saline and artificial sweat. Tannic acid (TA) and partially reduced graphene oxide (p-rGO) were further incorporated to improve interfacial adhesion, network energy dissipation, and electrical conduction. The resulting hydrogel exhibited a low equilibrium swelling ratio of 4.36% after long-term immersion in physiological saline and maintained a similarly low swelling ratio of approximately 4.56% in standard artificial sweat, demonstrating robust environmental stability under simulated sweating conditions. The optimized electrode also showed an ionic conductivity of 1.54 S/m and skin-relevant adhesion strength of 11.36 kPa on porcine skin, enabling conformal attachment to curved and deformable body surfaces. Mechanical tests indicated that the hydrogel possessed a skin-matched modulus and good cyclic deformation tolerance, which was favorable for reducing motion-induced interfacial fluctuation during dynamic monitoring. Based on the developed hydrogel electrode, a portable sEMG acquisition system was established. The system integrated differential amplification, anti-aliasing filtering, analog-to-digital conversion, and wireless data transmission, and the sampling rate was set at 450 Hz to cover the characteristic frequency range associated with muscle fatigue. Compared with commercial Ag/AgCl electrodes, the hydrogel electrode produced stable and clearly distinguishable sEMG waveforms during both hand and leg movements. The signal-to-noise ratios reached 35.66 dB for forearm signals and 36.46 dB for leg signals, indicating high-fidelity bioelectrical signal acquisition. During a 60 min stability test under aqueous conditions, no obvious signal attenuation was observed, suggesting that the anti-swelling polyelectrolyte network contributed to maintaining stable interfacial impedance. Finally, a 30 min isometric grip fatigue experiment was performed to evaluate the capability of the electrode for physiological monitoring. Time-domain and frequency-domain features were extracted through RMS analysis and Welch power spectral density estimation. As fatigue developed, the RMS value gradually increased, while the median frequency shifted from 64.2 Hz to 58.3 Hz, reflecting the typical spectral compression caused by reduced muscle fiber conduction velocity. These results demonstrate that the proposed polyelectrolyte hydrogel electrode can simultaneously achieve anti-swelling stability, wet adhesion, mechanical compliance, and high-quality sEMG acquisition. This work provides a feasible material and device strategy for wearable health monitoring, rehabilitation training, and human-machine interaction in humid or aqueous environments.
关键词
表面肌电 /
聚电解质水凝胶 /
界面黏附 /
抗溶胀 /
双网络结构 /
疲劳评估
Key words
surface electromyography /
polyelectrolyte hydrogel /
interfacial adhesion /
anti-swelling /
double-network structure /
fatigue assessment
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基金
福建省医药卫生科技领域创新联合资金项目（2025Y9591）; 福建省科技重大专项（2024HZ022013）; 国家自然科学基金项目（52575458,52405424）
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