纺织学报, 2026, 47(03): 118-128 doi: 10.13475/j.fzxb.20250902201

智能健康监测纺织品

血管监测用纤维基压电传感器的构建及性能评价

郭一铭1,2, 喻爽1,2, 赵帆,1,2, 王富军1,2

1 东华大学 纺织学院, 上海 201620

2 东华大学 纺织面料技术教育部重点实验室, 上海 201620

Construction and performance evaluation of fiber-based piezoelectric sensors for vascular monitoring

GUO Yiming1,2, YU Shuang1,2, ZHAO Fan,1,2, WANG Fujun1,2

1 College of Textiles, Donghua University, Shanghai 201620, China

2 Key Laboratory of Textile Science & Technology, Ministry of Education, Donghua University, Shanghai 201620, China

通讯作者: 赵帆(1990—),男,研究员,博士。主要研究方向为生物医用纺织材料。E-mail:zhaofan@dhu.edu.cn。

收稿日期: 2025-09-8   修回日期: 2026-01-25  

基金资助: 中央高校基本科研业务费专项资金资助项目(2232024G-01)
国家自然科学基金青年科学基金项目(52303310)

Received: 2025-09-8   Revised: 2026-01-25  

作者简介 About authors

郭一铭(2000—),男,硕士生。主要研究方向为自供电医用纤维器件。

摘要

为解决现有血管疾病术后监测方法如血管造影、核磁共振等需要大型设备且繁琐操作、缺乏持续监测方法的问题,采用左旋聚乳酸(PLLA)开发了可持续监测血管疾病修复状态的柔性植入式传感器。针对PLLA压电输出性能较低且调控机制尚不明确的问题,通过改变静电纺丝参数和热处理参数系统探究了纤维形貌和分子结构对PLLA纳米纤维膜压电性的影响规律。结果表明:纤维形貌和结晶度都会影响PLLA纳米纤维膜的压电输出性能;纤维直径越细且无串珠结构的PLLA压电输出性能最好;在纤维形貌良好时,PLLA的输出压电随α相晶型结晶度的提高而增大;纤维膜经热处理后出现α'晶型,提高了其结晶度,但导致压电性能降低;最优参数下PLLA纳米纤维膜的输出电压为2.933 V(87.7 N,1 Hz),电流为766.26 nA,电荷密度为1.95 μC/m2,最大输出功率密度为4.23 mW/m2,且在8.3~186.4 kPa范围内保持优异的线性度。体外血管模拟结果证实,该柔性传感器可有效感知环状脉动应变。

关键词： 压电传感器; 柔性传感器; 左旋聚乳酸; 静电纺丝; 压电性能; 脉动监测; 生物医用纺织品; 纳米纤维膜

Abstract

Objective Postoperative monitoring of vascular diseases is crucial for evaluating repair efficacy and preventing complications. However, existing clinical monitoring methods are associated with inherent limitations, including reliance on large-scale equipment, cumbersome operational procedures, and the lack of continuous monitoring capability. In order to address these pressing issues, this study aims to develop a flexible implantable sensor based on poly(L-lactic acid) (PLLA) that enables long-term, continuous monitoring of the repair status of vascular diseases. PLLA was selected as the core material by virtue of its excellent biocompatibility, biodegradability, and inherent piezoelectric properties, which are essential for constructing implantable devices with minimal biological side effects.

Method Although PLLA is a medically degradable material with intrinsic piezoelectricity, the nanofiber membranes fabricated via electrospinning typically exhibit low piezoelectric output, which severely restricts their practical application in sensor devices. Moreover, the underlying mechanism regulating the piezoelectric properties of PLLA nanofibers remains unclear. In order to overcome these short comings, a systematic experimental approach was adopted. In particular, different electrospinning parameters and post-treatment conditions were selected to fabricate a series of PLLA nanofiber membranes. Comprehensive characterizations were performed to investigate the influences of these parameters on the fiber morphology and molecular crystal structure of the PLLA nanofibers, as well as their subsequent impacts on piezoelectric performance.

Results The experimental results demonstrated that both fiber morphology and crystallinity are critical factors governing the piezoelectric output performance of PLLA nanofiber membranes. PLLA nanofibers with a smaller and more uniform diameter exhibited the optimal piezoelectric response, as such morphological features facilitate the efficient generation and transmission of piezoelectric charges. When the fiber morphology was maintained at an optimal state, the piezoelectric output of PLLA nanofibers increased linearly with the enhancement of α-phase crystallinity. In contrast, heat treatment of the nanofibers induced the formation of α'-phase crystals, and notably, an increase in α'-phase crystallinity led to a significant decrease in piezoelectric performance. Under the optimized electrospinning and post-treatment parameters, the PLLA nanofiber membrane achieved a maximum output voltage of 2.933 V (under the condition of 87.7 N load and 1 Hz frequency), an output current of 766.26 nA, a charge density of 1.95 μC/m2, and a maximum output power of 4.23 mW/m2. Furthermore, the sensor maintained linearity in the pressure range of 8.3-186.4 kPa, which fully covers the physiological pressure range of human blood vessels, indicating its suitability for vascular pressure monitoring applications. Additional tests using an in vitro vascular simulation device confirmed that the flexible PLLA sensor could effectively perceive cyclic pulsating strains similar to those generated by blood vessel contraction and relaxation.

Conclusion This study clarifies the regulatory mechanisms of the piezoelectric performance of PLLA nanofiber membranes and optimizes such performance via parameter modulation. Specifically, fiber morphology and crystallinity are confirmed as key determinants: smaller fiber diameters without bead-like structures enhance piezoelectric output; with favorable morphology, output increases with α-phase crystallinity, while α'-phase formation after heat treatment reduces piezoelectricity despite higher crystallinity. Under optimal parameters, the PLLA nanofiber membrane achieves 2.933 V output voltage (87.7 N, 1 Hz), 766.26 nA current, 1.95 μC/m2 charge density, 4.23 mW/m2 maximum output power, and excellent linearity under 8.3-186.4 kPa. In vitro vascular simulation tests verify its feasibility for practical monitoring by effectively sensing cyclic pulsating strain. Collectively, the PLLA-based flexible implantable sensor exhibits excellent sensitivity, stability, and biocompatibility, meeting the demands of real-time continuous postoperative vascular repair monitoring. It thus holds great clinical application potential, offering a novel solution to the limitations of existing clinical monitoring methods.

Keywords： piezoelectric sensor; flexible sensor; poly (L-lactic acid); electrospinning; piezoelectric property; pulsation monitoring; biomedical textiles; nanofiber membrane

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本文引用格式

郭一铭, 喻爽, 赵帆, 王富军. 血管监测用纤维基压电传感器的构建及性能评价[J]. 纺织学报, 2026, 47(03): 118-128 doi:10.13475/j.fzxb.20250902201

GUO Yiming, YU Shuang, ZHAO Fan, WANG Fujun. Construction and performance evaluation of fiber-based piezoelectric sensors for vascular monitoring[J]. Journal of Textile Research, 2026, 47(03): 118-128 doi:10.13475/j.fzxb.20250902201

心血管疾病(CVD)及其并发症是全球人类主要死因之一[1-2]。病情严重时往往需要通过手术治疗,但术后短期内仍易引发血管硬化、狭窄甚至闭塞,进而导致手术失败[3-5]。此类术后并发症常伴随血管压力波动,如果能动态精准监测患者血管压力水平并实施针对性监护,就能及时发现病变及血栓形成,并加以救治。与传统术后监测方法如血管造影、核磁共振等相比,植入式柔性压电传感器无需外部供电,可实时精确监测患者血流动力学信号,且不会限制患者活动[6]。当前该领域多采用不可降解的聚偏氟乙烯(PVDF)基纤维材料[7],针对短期监测场景通过二次手术取出,存在潜在临床风险,因此,研发一种可在术中植入以监测血管脉动波形变化的可降解自供电纤维传感器,具有重要的临床应用价值。

左旋聚乳酸(PLLA)是一类具备优良生物相容性与生物降解性的有机压电材料,可用于体内植入式自供电传感器的研发[8]。但相较于铁电PVDF基材料来说,PLLA的压电输出性能较弱,导致其在压力与应变监测中的精度及灵敏度偏低,因此提升PLLA的压电输出性能已成为近年研究热点。静电纺丝是制备PLLA纳米纤维的常用技术。当外部电场施加到PLLA上时,其带电官能团受到电场力作用,诱导PLLA聚合物链沿电场线方向伸长和排列,调控纤维结构和性能。Tai等[9]制备了直径为30~500 nm的取向PLLA纳米纤维,研究发现,纤维直径减小可强化压电偶极子的取向,进而提升材料的电压输出性能;其中30 nm样品的电压输出约为500 nm样品的8倍。刘古月等[10]探究纺丝电压对PLLA静电纺丝过程及纤维性能的影响发现:低电压下电场力不足,难以克服纺丝液的表面张力,导致纺丝液无法有效牵伸;高电压则会使射流速度过快,同样不利于纺丝液的稳定牵伸与分裂;18 kV为最优纺丝电压,可获得形貌优良且压电输出最高的纤维膜。Cuong等[11]证实,在PLLA的玻璃化转变温度以上进行热退火处理,能有效改善纤维膜的形貌规整性并提高其结晶度,进而提升其力学及压电性能。

尽管PLLA压电性能优化研究已取得诸多进展,但对压电性能的调控机制仍不明确。目前普遍认为PLLA的压电性能来源于其主链酯基中的C＝O偶极子,其中氧原子带负电,碳原子带正电,二者形成了偶极矩。PLLA具有α、α'、β、γ 4种不同的晶体结构[12-13]。其中α和α'晶体形式是热力学稳定构象,β相需经力学拉伸形成。研究指出,α和α'-PLLA中C＝O偶极子沿主链随机取向,极化互相抵消,导致压电性能较弱[9,14-15]。β-PLLA中偶极子呈有序排列,表现出高且稳定的压电性能,因此认为需将10/3螺旋结构的α相转变为3/1螺旋结构的β相,才能提升PLLA的压电性能[16-17]。但也有研究认为α-PLLA具有良好的压电输出性能,α'晶型因结构问题,其纤维内互连性易被非晶区破坏,形成阻碍电子迁移、降低电导率的电子陷阱,而α晶型的晶体互连且紧密堆积,能显著减少非晶区的破坏作用,因此认为促进α晶型形成并提高结晶度利于优化压电性能[18-20],且β-PLLA与压电性均为拉伸作用的结果,β相并非压电性的必要条件[21]。综上,系统探究不同分子结构下PLLA的压电特性,对揭示其压电来源及调控机制具有重要意义。

基于此,本研究通过改变PLLA静电纺丝过程中纺丝液的质量分数、溶剂配比、纺丝电压以及热处理温度,系统探究提高其压电性能的方法;结合纳米纤维膜的微观形貌、结晶结构、化学特性与压电输出性能,明确静电纺丝参数对PLLA压电性能的调控规律。此外,进一步结合封装技术构建PLLA柔性压电传感器,并在体外脉动模型上开展血管脉动应变的实时、连续化监测研究。

1 实验部分

1.1 实验材料

左旋聚乳酸(PLLA)颗粒(重均分子量为850 000),购自济南岱罡生物工程有限公司;N,N-二甲基甲酰胺(DMF)、二氯甲烷(DCM),购自国药集团化学试剂有限公司;铜电极,购自上海浩铁电子科技有限公司;模拟血管,购自杭州远点商贸有限公司。

1.2 纳米纤维膜的制备

首先,称取适量PLLA粉末溶解于DCM溶剂中,在30 ℃下磁力搅拌20 min。之后,将适量DMF溶剂加入该混合溶液中,在30 ℃下磁力搅拌 1 h,配制成纺丝液。随后,将纺丝液装入10 mL K50针管注射器(天津科迈生物科技有限公司)中进行静电纺丝。工艺参数设定如下:纺丝液推进速度4 mL/h,接收距离15 cm,滚筒转速140 r/min,环境相对湿度20%~30%,纺丝温度25~35 ℃。纺丝结束后,将所得纤维膜置于30 ℃烘箱中干燥3 d,备用。

探究纺丝液质量分数影响时,PLLA质量分数分别设置为2%、4%和6%;探究溶剂配比影响时,将DCM和DMF体积比分别设置为6∶4、7∶3、8∶2、9∶1和10∶0;探究纺丝电压影响时,将电压分别设置为15、18.5、22 kV。探究热处理温度影响时,将纤维膜分别放入30、100、150 ℃烘箱中干燥8 h。

1.3 压电传感器的制备

为测试纳米纤维膜的压电输出性能,将制备的纳米纤维膜切割成2.5 cm×2.5 cm尺寸,在其上下表面分别附着直径为2 cm的铜电极,从铜电极表面分别引出宽度为0.5 cm的铜条作为输出导线。最后,将整个压电传感器用聚酰亚胺薄膜封装。

1.4 测试与表征

1.4.1 纳米纤维膜形貌与结构表征

采用FLEX 1000型场发射扫描电子显微镜(日本株式会社日立制作所)观察纳米纤维膜的形貌。

采用Bruker D8型X射线衍射仪(德国布鲁克公司)表征纳米纤维膜的结晶结构,扫描速度为5(°)/min,扫描范围(2θ)为2°~90°,电压为40 kV,电流为50 mA。

采用Nicolet 6700型傅里叶红外显微成像光谱仪(美国赛默飞公司)表征纤维膜的化学结构,扫描范围为4 000~400 cm-1,分辨率为4 cm-1。

采用STA8000型差示扫描量热仪(美国珀金埃尔默公司)分析纤维膜的结晶度,在N2气氛中加热,以10 ℃/min从0 ℃加热到210 ℃,根据DSC曲线计算结晶度,公式如下:

${X}_{c}=\frac{△{H}_{m}^{f}-△{H}_{m}^{c}}{△{H}_{100\%}^{f}}\times 100\%$

式中:Xc为结晶度,%;$△{H}_{m}^{f}$为熔融峰积分确定的熔融热,J/g;$△{H}_{m}^{c}$为冷结晶峰积分确定的冷结晶热,J/g;$△{H}_{100\%}^{f}$为100%结晶PLLA材料的熔融热,取值93.1 J/g[22]。

1.4.2 纳米纤维膜压电输出性能测试

采用Linmot-PS01-37×120-C型直线电机(德国LINMOT公司)作为施力系统,采用Keithley-6517B型静电计系统(美国吉时利公司)测量纳米纤维膜在1 Hz频率下的开路电压、短路电流和输出电荷。

1.4.3 纳米纤维膜体外血管模拟测试

将压电传感器固定在模拟血管上,用硅胶管连接模拟血管与蠕动泵,形成闭环系统,模拟血流环境。通过DDBT-201智能型蠕动泵(上海之信仪器有限公司)模拟血管收缩膨胀行为。采用静电计系统测量纳米纤维膜在不同频率和不同血管直径下的压电输出性能。

2 结果与讨论

2.1 纺丝参数对纤维膜形貌和结构的影响

2.1.1 PLLA质量分数的影响

为探究PLLA质量分数对静电纺纤维膜微观形貌及纤维直径的影响,设置 PLLA 质量分数为 2%、4% 和 6%,并固定DCM与 DMF体积比为6∶4、纺丝电压 15 kV、热处理温度 30 ℃,结果如图1、2 所示。由图2可知:随PLLA质量分数增加,纤维直径显著提升。PLLA质量分数为2%、4%、6%制备的纳米纤维膜的纤维平均直径d分别为(0.325±0.071)、(0.537±0.103)、(1.513±0.355)μm。当PLLA质量分数为2%时,纤维虽然直径最细,但其易形成串珠结构。这一现象的成因与纺丝液黏度变化直接相关:随PLLA质量分数增加,纺丝液黏度相应升高,聚合物链的缠结程度随之增大;反之,低质量分数下纺丝液黏度偏低,分子链缠结度不足,在静电纺丝过程中受到的静电拉伸力分布不均,导致分子链取向协同性较差,最终促使串珠结构的形成[9]。当PLLA质量分数为4%时,所制备的纤维具有更规整的形貌及较低的直径。

图1

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图1   不同PLLA质量分数下纳米纤维膜的扫描电镜照片

Fig.1   SEM images of nanofiber membranes with different PLLA mass fractions


图2

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图2   不同PLLA质量分数下纳米纤维膜的直径分布图

Fig.2   Diameter distribution diagrams of nanofiber membranes with different PLLA mass fractions


图3(a)示出不同质量分数下纳米纤维膜的XRD谱图。由图可知:所有样品均在2θ为16.7°处出现尖峰,对应α相的(200)/(110)晶面;其中6%PLLA质量分数样品的吸收峰强度高于2%和4%样品,表明6%PLLA质量分数下纤维膜的晶相含量最高[23-24]。此外,所有样品中均未检测到β相或α'相的特征峰。

图3

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图3   不同PLLA质量分数下纳米纤维膜的结晶结构与化学结构

Fig.3   Crystalline structures and chemical structure of nanofiber membranes with different PLLA mass fractions. (a) XRD pattern; (b) FT-IR spectra; (c) DSC curves


图3(b)为不同PLLA质量分数下纳米纤维膜的红外光谱图。其中,1 045 cm-1处的吸收峰对应C—CH3的伸缩振动;1 092 cm-1处为C—O—C的对称伸缩振动峰;1 134 cm-1处为—CH3的不对称面内摇摆振动峰;1 213 cm-1处为C—O—C不对称伸缩与—CH3的不对称面内摇摆振动的耦合吸收峰,上述特征峰均归属于PLLA α相[9,11,25]。所有光谱中均未观察到对应PLLA β相的912 cm-1处的特征谱带,该结果与XRD分析结果相一致。

图3(c)示出不同质量分数下纳米纤维膜的DSC曲线。由图可知,2%、4%、6%PLLA质量分数下纤维膜的结晶度分别为44.11%、43.12%、50.18%,这与XRD分析结果相吻合,证实高PLLA质量分数下更易制备出结晶度较高的纳米纤维膜。值得注意的是,2%PLLA质量分数样品的结晶度未出现明显下降,推测其原因是串珠结构的形成导致纤维膜中纤维直径分布不均,进而影响了纤维膜的整体结晶特性。

2.1.2 溶剂配比的影响

为探究溶剂配比对静电纺纤维膜微观形貌及纤维直径的影响,设置DCM与DMF体积比分别为6∶4、7∶3、8∶2、9∶1和10∶0,并固定PLLA质量分数为4%、纺丝电压为15 kV、热处理温度为30 ℃,所得结果如图4、5所示。

图4

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图4   不同溶剂配比下纳米纤维膜的扫描电镜照片

Fig.4   SEM images of nanofiber membranes at different solvent ratios


图5

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图5   不同溶剂配比下纳米纤维膜的直径分布图

Fig.5   Diameter distribution diagrams of nanofiber membranes with different solvent ratios


由图4(e)可见,10∶0溶剂配比下纤维以串珠形态存在,无法准确测定其直径分布,且纤维膜强度过低,难以满足后续结晶结构与化学特性分析的需求,因此后续表征仅针对其它4组溶剂配比展开。由图5可知:不同DCM与DMF体积比下,纤维平均直径d分别为(0.537 ± 0.103)μm(6∶4)、(0.575 ± 0.124)μm(7∶3)、(0.496 ± 0.143)μm(8∶2)、(0.409 ± 0.126)μm(9∶1)。尽管9∶1体积比下纤维直径最细,但易形成串珠结构。这是由于DCM是PLLA的良溶剂,当PLLA仅溶解于DCM时,溶液黏度较低,且在纺丝过程中DCM会快速挥发,最终导致纤维呈现串珠且多孔的形貌;而DMF的加入则可有效抑制DCM的快速挥发[26],因此随着DMF占比的提高,纤维直径呈现出相应的增大趋势。

图6(a)示出不同溶剂配比下纳米纤维膜的XRD谱图。所有样品均在2θ为16.7°处出现尖峰,对应α相的(200)/(110)晶面。其中9∶1溶剂体积比样品的吸收峰相较于6∶4、7∶3和8∶2体积比样品更弱,表明其晶相含量最低;所有样品中均未观察到β相或α'相特征峰。图6(b)示出不同溶剂配比下纳米纤维膜的红外光谱图,所有光谱中均未观察到对应PLLA β相的特征谱带。

图6

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图6   不同溶剂配比下纳米纤维膜的结晶结构与化学结构

Fig.6   Crystalline structures and chemical structure of nanofiber membranes at different solvent ratios. (a) XRD pattern; (b) FT-IR spectra; (c) DSC curves


图6(c)示出不同溶剂配比下纳米纤维膜的DSC曲线。由图可知,6∶4、7∶3、8∶2、9∶1这4种溶剂体积比下,纤维膜的结晶度分别为43.12%、47.15%、44.49%、45.29%。结合上述数据可推断,改变溶剂体积比对PLLA纳米纤维膜的结晶度影响较小。

2.1.3 纺丝电压的影响

为探究纺丝电压对静电纺纤维膜微观形貌及纤维直径的影响,设置纺丝电压分别为15、18.5、22 kV,并固定PLLA质量分数为4%、DCM与DMF体积比为6∶4、热处理温度为30 ℃,结果如图7、8所示。由图可知:纺丝电压对纤维直径无明显影响,纤维平均直径d分别为(0.537±0.103) μm (15 kV)、(0.535±0.116)μm(18.5 kV)、(0.520±0.109)μm(22 kV)。

图7

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图7   不同纺丝电压下纳米纤维膜的扫描电镜照片

Fig.7   SEM images of nanofiber membranes under different electrospinning voltages


图8

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图8   不同纺丝电压下纳米纤维膜的直径分布图

Fig.8   Diameter distribution diagrams of nanofiber membranes under different electrospinning voltages


图9(a)示出不同纺丝电压下纳米纤维膜的XRD谱图。所有样品均在2θ为16.7°处出现尖峰,对应α相的(200)/(110)晶面,且22、18.5 kV电压下样品的吸收峰相较于15 kV下更强,表明这2个电压条件下制备的纤维膜晶相含量更高。图9(b)示出不同纺丝电压下纳米纤维膜的红外光谱图,所有光谱中均未观察到对应PLLA β相的特征谱带。

图9

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图9   不同纺丝电压下纳米纤维膜的结晶结构与化学结构

Fig.9   Crystalline structures and chemical structure of nanofiber membranes under different electrospinning voltages. (a) XRD pattern; (b) FT-IR spectra; (c) DSC curves


图9(c)示出不同纺丝电压下纳米纤维膜的DSC曲线。由图可知,15、18.5、22 kV电压下纤维膜的结晶度分别为43.12%、49.01%、50.66%。该结果与XRD分析结果相一致,表明提高纺丝电压有利于提升PLLA纳米纤维膜的结晶度;但当纺丝电压过高时,不利于纺丝射流的牵伸与分裂[10],这也导致22 kV电压下纤维膜结晶度相较于18.5 kV下没有明显提升。

2.1.4 热处理温度的影响

为探究热处理温度对静电纺纤维膜微观形貌及纤维直径的影响,设置热处理温度分别为30、100、150 ℃,并固定PLLA质量分数为4%、DCM与DMF体积比为6∶4、纺丝电压为22 kV,所得结果如图10、11所示。由图11可知:热处理温度对纤维直径无明显影响,纤维平均直径d分别为(0.520±0.109)μm(30 ℃)、(0.505±0.113)μm(100 ℃)、(0.533±0.129)μm(150 ℃)。

图10

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图10   不同热处理温度下纳米纤维膜的扫描电镜照片

Fig.10   SEM images of nanofiber membranes at different heat treatment temperatures


图11

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图11   不同热处理温度下纳米纤维膜的直径分布图

Fig.11   Diameter distribution diagrams of nanofiber membranes at different heat treatment temperatures


图12(a)示出不同热处理温度下纳米纤维膜的XRD谱图。所有样品均在2θ为16.7°处出现尖峰,对应α相的(200)/(110)晶面,且随着热处理温度的升高,衍射峰强度更强,表明提高热处理温度有利于提高纤维膜的晶相含量。其中,经100、150 ℃热处理的样品在2θ为19.1°处出现尖峰,对应α'相的(203)晶面[11,23];经150 ℃热处理的样品在2θ为22.4°处另有尖峰出现,对应(210)晶面,说明该温度条件下能够形成结晶结构更完整的PLLA晶体[22,27]。

图12

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图12   不同热处理温度下纳米纤维膜的结晶结构与化学结构

Fig.12   Crystalline structures and chemical structure of nanofiber membranes at different heat treatment temperatures. (a) XRD pattern; (b) FT-IR spectra; (c) DSC curves


图12(b)示出不同热处理温度下纳米纤维膜的红外光谱图,在所有光谱中均未观察到对应PLLA β相的特征谱带。

图12(c)示出不同热处理温度下纳米纤维膜的DSC曲线。由图可知,当热处理温度为30、100、150 ℃时,纤维膜的结晶度分别为50.66%、53.58%、55.46%。该结果与XRD分析结果相一致,证实提高热处理温度可在一定程度上提升PLLA纳米纤维膜的结晶度。

2.2 纺丝参数对纤维膜压电性能的影响

固定施加压力87.7 N、频率1 Hz、负载电阻1×109 Ω,测试各纺丝参数下纤维膜的压电输出性能,结果如图13所示。

图13

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图13   不同纺丝条件下纳米纤维膜的输出电压

Fig.13   Output voltages of nanofiber membranes under different spinning conditions. (a) Under different mass fraction; (b) Under different solvent ratio; (c) Under different spinning voltage; (d) Under different heat treatment temperature


图13(a)示出PLLA质量分数对纤维膜压电性能的影响。不同PLLA质量分数下纤维膜的平均压电输出分别为(0.883±0.076)V(2%)、(2.300±0.100)V(4%)、(1.267±0.058)V(6%)。结合图1~3对表观形貌和分子结构的分析可知,纤维直径对压电性能的影响显著高于结晶度。纤维直径变细源于聚合物链受到良好的拉伸作用,这一过程可促使压电偶极子取向排列,进而有利于获得高压电性能[9];而串珠结构会导致聚合物链排列混乱,进而导致压电输出显著降低。

图13(b)示出DCM与DMF体积比对纳米纤维膜压电性能的影响。不同溶剂配比下的平均压电输出分别为(2.300±0.100)V(6∶4)、(2.267±0.208)V(7∶3)、(2.650±0.229)V(8∶2)、(1.267±0.208)V(9∶1)。结合图4~6可知,在纤维形貌和结晶结构相似的前提下,不同溶剂配比对压电性能无明显影响,具体表现为6∶4、7∶3、8∶2这3种体积比下的压电输出无显著性差异;而当纤维形貌和结晶完整度被破坏时,会导致压电性能显著下降,具体表现为9∶1体积比下的压电输出性能显著降低。

图13(c)示出纺丝电压对纳米纤维膜压电性能的影响。不同电压下的平均压电输出分别为(2.300±0.100)V(15 kV)、(2.867±0.231)V(18.5 kV)、(2.933±0.116)V(22 kV)。结合图7~9可知,在纤维形貌相似的前提下,结晶结构对压电性能的影响更为明显。结晶度提高有助于聚合物链规整排列,使偶极矩方向更趋于一致,从而使纤维膜表现出更强的压电性能[28-29]。

图13(d)示出热处理温度对纳米纤维膜压电性能的影响。不同温度下的平均压电输出分别为(2.933 ± 0.116)V(30 ℃)、(1.567 ± 0.252)V(100 ℃)、(0.250 ± 0.050)V(150 ℃)。结合图10~12可知,当α'晶型出现时,其结晶度提高不利于压电性能的提升。这是由于α'相自身的结构特性,其在纤维中的互连性易被非晶区破坏,且α'相的存在会阻碍电子迁移、降低电导率的电子陷阱,最终导致压电输出降低;而α晶型晶体互连性良好且堆积紧密,能最大限度减小非晶区对其互连性的破坏,更有利于维持纤维膜较好的压电性能。

基于以上结果可知,纤维直径、纤维形貌和结晶度均显著影响PLLA纳米纤维膜的压电输出性能,具体表现如下:1)纤维直径变细源于聚合物链受到良好的拉伸作用,这一过程可促使偶极子高度取向排列,进而有利于获得高压电性能;2)压电PLLA纳米纤维膜的主要晶型为α相,该晶型晶体互连且紧密堆积,因此提高其结晶度有利于分子链规整排列,使偶极矩方向趋于一致,从而优化压电性能;而当α'晶型出现时,提高其结晶度不利于压电性能的提高;3)PLLA的压电性能并非单纯随结晶度的提高而增强,较细直径、光滑表面形貌和特定晶相这些因素对压电性能的影响程度高于结晶度的单一作用。

2.3 压电传感器的输出性能

图14示出以最优纺丝参数(PLLA质量分数4%、DCM与DMF体积比为6∶4、纺丝电压22 kV、热处理温度30 ℃)制备的PLLA压电传感器的输出性能。如图14(a)~(c)所示,该传感器的平均压电输出为2.933 V,平均短路电流为766.26 nA,平均输出电荷为1.22 nC,据此计算其电荷密度为1.95 μC/m2。从图14(d)可看出,压电传感器在连续击打2 500次后,压电输出仍保持稳定。由图14(e)可见,该传感器在8.3~186.4 kPa范围内可保持优异的线性度,灵敏度为0.014 V/kPa。在压电传感器的实际应用中,输出功率取决于负载本身的电阻,因此,对PLLA压电传感器在1×104~1×1010 Ω负载范围内的功率密度变化进行表征,结果如图14(f)所示。可知,当负载电阻为1×109 Ω时,传感器达到最大功率密度,为4.23 mW/m2。

图14

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图14   PLLA压电传感器的输出性能

Fig.14   Output performance of PLLA piezoelectric sensor. (a) Output valtage; (b) Short-circuit current; (c) Output charge; (d) Stability of piezoelectric output; (e) Piezoelectric output under different pressures; (f) Output power density


2.4 压电传感器的体外模拟血管监测应用

为证明PLLA压电传感器的实用性,构建了一套体外血管模拟系统,如图15(a)所示,不同血管模拟条件下获得的输出电压如图15(b)~(f)所示。

图15

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图15   PLLA压电传感器在不同血管模拟条件下获得的电压

Fig.15   Voltage obtained by PLLA piezoelectric sensor under different vascular simulation conditions. (a) In vitro blood vessel simulation system;(b) Simulated blood vessel diameter;(c) Peristaltic pump flow rate; (d) Simulated vessel occlusion;(e) Simulated suture;(f) Simulated thrombosis


图15(b)示出压电传感器在不同模拟血管直径下的监测结果。不同模拟血管直径对应的平均输出电压分别为2.14 V(外径8 mm)、3.34 V(外径13 mm)、4.39 V(外径20 mm)。分析可知,血管直径越粗,在相同血压下产生的形变越大,对应的传感器输出电压也越高。图15(c)示出压电传感器在不同脉动频率下的监测结果。通过改变蠕动泵的流速可模拟血管的搏动频率,不同流速下的平均输出电压分别为3.34 V(500 mL/min)、3.53 V(1 000 mL/min)、3.51 V(1 500 mL/min)。图15(d)示出压电传感器对血管阻塞的监测结果。采用镊子夹紧血管以模拟血管阻塞情况,结果显示,当血管受到阻塞时,传感器输出电压显著降低且呈现出不稳定波形;当阻塞解除、血管恢复正常后,输出电压也恢复至正常水平。图15(e)示出压电传感器对缝合血管的监测结果。将模拟血管剪开后用生物胶水重新黏合,模拟血管缝合场景,此时平均输出电压由正常血管的3.34 V降低至缝合后的2.25 V。这是由于重新黏合后血管形变能力下降,进而导致传感器输出电压减小。图15(f)示出压电传感器对血管栓塞的监测结果。在模拟血管内放置1颗与其直径相当的硬质石块模拟栓塞,此时平均输出电压由正常血管的3.34 V降低至栓塞后的0.65 V。这是由于栓塞后血管形变减小,导致输出电压降低。上述结果表明,该传感器可实现对模拟血管直径、脉动频率、血管狭窄、缝合血管、血栓阻塞的监测,在血管术后监测领域具有良好的应用潜力。

3 结论

本研究通过调控静电纺丝参数,系统探究了左旋聚乳酸(PLLA)纳米纤维膜的微观形貌、结晶结构、化学特性与压电输出性能之间的关系,结果表明:仅形成α晶型的PLLA纳米纤维膜表现出优异的压电性能;纤维直径、纤维形貌和结晶度均对纤维膜的压电输出强度有显著影响,其中纤维直径越细且无串珠结构的PLLA压电输出性能最优;在纤维形貌一定时,PLLA的压电输出随α相结晶度的提高而增大;但当纤维经热处理形成α'晶型时,其结晶度的提高反而会抑制压电性能;以最优纺丝参数(PLLA质量分数4%,DCM与DMF体积比为6∶4,纺丝电压22 kV,30 ℃干燥)制备的压电传感器,其输出电压达2.933 V、短路电流达766.26 nA、电荷密度达1.95 μC/m2、功率密度达4.23 mW/m2。该传感器在体外模拟血管监测中,表现出高输出电压和明显的波形差异,可实现对模拟血管直径、脉动频率、血管狭窄、缝合血管、血栓阻塞的监测,有望作为可植入柔性传感器用于血管疾病术后实时连续监测。

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Cisplatin is an effective chemotherapeutic drug, but it generates reactive oxygen species (ROS) that induce severe adverse effects such as ototoxicity. Resveratrol reportedly prevents oxidative stress-induced cell death. Thus, we hypothesized that the anti-oxidative effect of resveratrol could protect against cisplatin-induced ototoxicity. The present study examined the protective effect of resveratrol against cisplatin-induced ototoxicity in HEI-OC1 auditory cells.HEI-OC1 cells were pretreated with resveratrol at 1μM for 24h and then exposed to 15μM cisplatin for 48h. Resulting cytotoxicity was measured by the MTT method, and intracellular ROS was measured using flow cytometry. Protective effect of resveratrol was compared with other anti-oxidants.Pretreatment with resveratrol 1μM protected HEI-OC1 auditory cells against cisplatin-induced cytotoxicity and significantly reduced a cisplatin-induced increase in ROS. Resveratrol provided significant protection against 15μM cisplatin applied for 48h (50.8% cell viability in the cisplatin group vs. 57.6% in the cisplatin-plus-resveratrol group), and there was a 9% decrease in cisplatin-induced ROS associated with resveratrol.This is the study investigating the protective effects of resveratrol against cisplatin-induced ototoxicity in an auditory cell line. Resveratrol significantly reduced a cisplatin-induced increase in ROS and thereby inhibited cisplatin-induced cytotoxicity.Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

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In this investigation, the chain conformation transformation of the piezoelectric polymer of a poly(L-Lactic Acid) (PLLA) film was analyzed under an electric field for the first time using infrared spectroscopy. It is revealed that the piezoelectric shear mode coefficient d14 (∼10 pC/N) of a stretched α form PLLA film mainly comes from the rotation of C  O dipoles inside the polymer main chain. The reorientation of the dipoles causes the deformation of the crystal structure, which corresponds to a shear mode strain macroscopically in the PLLA film along a 45° direction to the polymer length. The back-bone of the molecular chain keeps its own conformation of a 103 helix under an external field up to 100 MV/m.

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