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Flexible and strain conductive cotton yarn enabled by low-temperature sintering of silver paste with multifunctional sensing capability in human motion detection and wearable applications
通过银浆低温烧结实现的柔性和应变导电棉纱，在人体运动检测和可穿戴应用中具有多功能传感功能

Xiaoqiang Li a, ∗ a,  ∗ ^("a, ")^(**){ }^{\text {a, }}{ }^{*}, Xinke Li a a  ^("a "){ }^{\text {a }}, Mengjia Wang a a  ^("a "){ }^{\text {a }}, Riquan Zheng a a  ^("a "){ }^{\text {a }}, Yang Jin a a  ^("a "){ }^{\text {a }}, Zhijie Gu b b  ^("b "){ }^{\text {b }}
李 a, ∗ a,  ∗ ^("a, ")^(**){ }^{\text {a, }}{ }^{*} 小强 ， 李 a a  ^("a "){ }^{\text {a }} 欣科 ， 王 a a  ^("a "){ }^{\text {a }} 梦佳 ， 郑日全 a a  ^("a "){ }^{\text {a }} ， 金洋 a a  ^("a "){ }^{\text {a }} ， 顾 b b  ^("b "){ }^{\text {b }} 志杰 a a  ^("a "){ }^{\text {a }} School of Textile Science and Engineering, Jiangnan University, Wuxi 214122, China
a a  ^("a "){ }^{\text {a }} 江南大学 纺织科学与工程学院， 江苏 无锡 214122 b b ^(b){ }^{\mathrm{b}} Zhejiang Feiyi Photoelectric Energy Technology Co Ltd, Ningbo 315700, China
b b ^(b){ }^{\mathrm{b}} 浙江飞逸光电能源股份有限公司， 浙江 宁波 315700

ARTICLE INFO  文章信息

Keywords:  关键字：

Low-temperature sintering
低温烧结
Conductive yarn  导电纱
Wearable strain sensor  可穿戴应变传感器
Silver paste  银浆
Micro-vibration detection
微振动检测

Abstract  抽象

Flexible wearable textiles have attracted increasing attention, due to their potential applications in human motion detection, electric heating and humidity monitoring. However, the rigidity of metal materials contradicts the flexibility of textiles, and the complex preparation process and unfriendly environment hinder the development of metal materials as conductive materials of smart textiles. This study proposed a simple and environmentally friendly solution for smart textile preparation. Drawing on the bionic design principle of longhorned beetle’s exocuticle, the conductive layer on the surface of cotton yarn (CY) was formed by sintering the silver paste under low temperature of 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C}. Silver Paste (SP) mainly composed with silver particles, terpineol (TE) and ethyl cellulose (EC). The resultant conductive yarn was characterized with high flexibility and high conductivity ( 4.08 × 10 3 S / cm 4.08 × 10 3 S / cm 4.08 xx10^(3)S//cm4.08 \times 10^{3} \mathrm{~S} / \mathrm{cm} ). The conductivity of the yarn increases under tensile force, while decreases under non-tensile bending action. The strain sensor prepared by the yarn has a wide working range and high sensitivity, with distinguish performances of signal output according to the motion of different human body parts. The sensing behavior was also highlighted with the capability of micro-vibration strain of the human body, such as response to the pulse and throat. Furthermore, the conductive property of sintered silver paste cotton yarn (SSP-CY) has the capability of electric heating. The electric heating device based on SSP-CY can realize wired and radio heating, which resulted a maximum temperature of about 41 ∘ C 41 ∘ C 41^(@)C41^{\circ} \mathrm{C}. Therefore, the novel conductive cotton yarn has great potential in the application of high-sensitive wearable electronic devices.
柔性可穿戴纺织品因其在人体运动检测、电加热和湿度监测方面的潜在应用而受到越来越多的关注。然而，金属材料的刚性与纺织品的柔韧性相矛盾，复杂的制备工艺和不友好的环境阻碍了金属材料作为智能纺织品导电材料的发展。本研究提出了一种简单且环保的智能纺织品制备解决方案。借鉴长角甲虫外角质层的仿生设计原理，通过在低温下烧结银浆，形成棉纱 （CY） 表面的导电层 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} 。银浆 （SP） 主要由银颗粒、松油醇 （TE） 和乙基纤维素 （EC） 组成。所得导电纱线具有高柔韧性和高导电率 （ 4.08 × 10 3 S / cm 4.08 × 10 3 S / cm 4.08 xx10^(3)S//cm4.08 \times 10^{3} \mathrm{~S} / \mathrm{cm} ）。纱线的导电性在拉伸力下增加，而在非拉伸弯曲作用下降低。由纱线制备的应变传感器工作范围宽，灵敏度高，根据人体不同部位的运动，具有区分信号输出的性能。传感行为还通过人体的微振动应变能力（例如对脉搏和喉咙的响应）而得到强调。此外，烧结银浆棉纱 （SSP-CY） 的导电性能具有电加热能力。基于SSP-CY的电加热装置可以实现有线和无线电加热，最高温度约为 41 ∘ C 41 ∘ C 41^(@)C41^{\circ} \mathrm{C} 。因此，新型导电棉纱在高灵敏度可穿戴电子设备中的应用具有巨大潜力。

1. Introduction  1. 引言

With the increasing demand of flexible wearable applications, a variety of smart textiles with rapid response to external stimuli have a wide application prospect in the field of human health monitoring [1,2], wearable electronic devices [ 3 , 4 ] [ 3 , 4 ] [3,4][3,4] and human motion monitoring [5,6]. Smart textiles have been developed with excellent flexibility and sensing properties based on different mechanisms, such as resistance [ 7 , 8 ] [ 7 , 8 ] [7,8][7,8], capacitance [9], piezoelectricity [10], triboelectricity [11] and inductance [12]. The substrates for preparing smart textile mainly focus on fiber [13-15], yarn [16], fabric [17,18] and film [19]. Among the abovementioned mechanisms, the resistance was the most used signal for the aim of motion detection. The sensors based on one dimensional materials, for example, fiber or yarn, sensor has the inherent porous structure and flexibility, enable them could be utilized into smart textile through
随着柔性可穿戴应用需求的不断增长，各种对外界刺激快速响应的智能纺织品在人体健康监测[1,2]、可穿戴电子设备 [ 3 , 4 ] [ 3 , 4 ] [3,4][3,4] 和人体运动监测[5,6]等领域具有广泛的应用前景。基于电阻 [ 7 , 8 ] [ 7 , 8 ] [7,8][7,8] 、电容 [9]、压电 [10]、摩擦电 [11] 和电感 [12] 等不同机制，智能纺织品已开发出具有出色柔韧性和传感性能的智能纺织品。制备智能纺织品的基材主要集中在纤维 [13-15]、纱线 [16]、织物 [17,18] 和薄膜 [19]。在上述机制中，电阻是用于运动检测目的的最常用信号。基于一维材料（例如纤维或纱线）的传感器具有固有的多孔结构和柔韧性，使其能够通过以下方式用于智能纺织品
weaving [20], knitting [21], and embroidery [22].
编织 [20]、编织 [21] 和刺绣 [22]。
The resistance-type of one-dimension sensor usually integrated with insulating filament as the framework material, and modified with conductive substances, such as conductive polymers, carbon, and metals. Poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT: PSS) is one of the typical conductive polymers[23]. Pattanarat et al., [24] combined PEDOT: PSS to modify cotton yarn; however, the resultant conductive yarns exhibited poor electrical conductivity of 76 S / cm S / cm S//cm\mathrm{S} / \mathrm{cm}, which limited its applications in the field of smart textile. Carbonbased conductive materials have better conductivity than conductive polymers. Zhang et al., [25] prepared the conductive yarn by dipcoating reduced graphene oxide (rGO) on the yarn surface. Dini et al., [26] used carbon nanotube (CNT) to prepare conductive yarn. However, CNT and rGO have poor dispersion and weak interaction with fiber substrates, also accompany with cumbersome, costly and
电阻型一维传感器通常以绝缘丝为框架材料集成，并用导电物质（如导电聚合物、碳和金属）进行改性。聚（3,4-乙烯二氧噻吩）：聚（4-苯乙烯磺酸盐）（PEDOT：PSS）是典型的导电聚合物之一[23]。Pattanarat et al.， [24] 结合 PEDOT：PSS 改性棉纱;然而，所得导电纱线的导电率较差，为 76 S / cm S / cm S//cm\mathrm{S} / \mathrm{cm} ，这限制了其在智能纺织领域的应用。碳基导电材料比导电聚合物具有更好的导电性。Zhang等[25]通过在纱线表面浸涂还原的氧化石墨烯（rGO）来制备导电纱线。Dini 等 [26] 使用碳纳米管 （CNT） 制备导电纱线。然而，CNT 和 rGO 分散性差，与纤维基材的相互作用弱，还伴随着繁琐、昂贵和
environmentally unfriendly processes. Therefore, metals with inherent high conductivity, low-cost and tractable properties, are the suitable material for electrode and smart textile manufacturing. Silver is remarkable of its high conductivity of ∼ 62 × 10 4 S / cm ∼ 62 × 10 4 S / cm ∼62 xx10^(4)S//cm\sim 62 \times 10^{4} \mathrm{~S} / \mathrm{cm}, has been thoroughly investigated to prepare smart textile combined with various filaments [27]. Tang et al., [28] reported conductive threads and fabrics by Ag-coated Cu modification. Usually, the loading of metal on to textile or yarn by means of physical vapor deposition (PVD) [29,30] and chemical vapor deposition (CVD) [31,32]; the demand of specialized instrument and high cost limit their practicability in preparation of smart textiles.
对环境不友好的过程。因此，具有固有高导电性、低成本和易处理特性的金属是电极和智能纺织品制造的合适材料。银以其高导电性而著称 ∼ 62 × 10 4 S / cm ∼ 62 × 10 4 S / cm ∼62 xx10^(4)S//cm\sim 62 \times 10^{4} \mathrm{~S} / \mathrm{cm} ，已被深入研究以制备与各种长丝结合的智能纺织品 [27]。Tang et al.， [28] 报道了通过 Ag 涂层 Cu 改性获得的导电线和织物。通常，通过物理气相沉积 （PVD） [29\u201230] 和化学气相沉积 （CVD） [31\u201232] 将金属负载到纺织品或纱线上;对专用仪器的需求和高成本限制了它们在智能纺织品制备中的实用性。
In order to improve the production efficiency and reduce the production costs, metal inks or metal paste was developed; and the conductive yarn could be manufactured by casting the ink or paste onto the cotton yarn. Hong et al., [33] developed a novel nano-silver ink, and finished a flexible and washable textile-based electrodes by screen printing. The conductive silver paste has a simple preparation process, without chemical synthesis, nor any burden of environment. Therefore, the conductive silver paste with the characteristics of simple process and environmental protection is one of the best choices for conductive materials. However, the surface coating method has some obvious defects. Silver particles are usually present in scales of micro- or nano-meters in the silver paste. After coating process, the silver particles often adhered to the surface of the yarn by polymer. Silver particles hardly directly contacted with each other, lead to the deduction of conductivity. In addition, the adhesion of silver particles to the yarn surface was very weak, which further limits the application in smart textiles. Therefore, it is necessary to develop a new preparation method to connect the silver particles after coating on the yarn, thereby improving the adhesion and electrical conductivity. Previous studies have found that silver in micron- or nano-scales can be sintered at low temperatures of < 250 ∘ C < 250 ∘ C < 250^(@)C<250^{\circ} \mathrm{C}, to form the connections between silver particles or flakes. This technology was known as low temperature sintering technology, which has been applied to the field of semiconductor thermal and electrical conduction [34].
为了提高生产效率和降低生产成本，开发了金属油墨或金属浆料;并且导电纱线可以通过将油墨或糊剂浇铸到棉纱上来制造。Hong 等人 [33] 开发了一种新型纳米银墨水，并通过丝网印刷完成了一种柔性且可水洗的纺织基电极。导电银浆制备工艺简单，无需化学合成，也不受任何环境负担。因此，具有工艺简单、环保等特点的导电银浆是导电材料的最佳选择之一。但是，表面涂层方法存在一些明显的缺陷。银颗粒通常以微米或纳米的刻度存在于银浆中。涂层过程后，银颗粒经常通过聚合物粘附在纱线表面。银颗粒之间几乎不直接接触，导致电导率降低。此外，银颗粒对纱线表面的粘附力很弱，进一步限制了在智能纺织品中的应用。因此，有必要开发一种新的制备方法，将涂布在纱线上的银颗粒连接起来，从而提高附着力和导电性。以前的研究发现，微米或纳米级的银可以在 < 250 ∘ C < 250 ∘ C < 250^(@)C<250^{\circ} \mathrm{C} 的低温下烧结，以形成银颗粒或薄片之间的连接。这项技术被称为低温烧结技术，已应用于半导体热传导和导电领域 [34]。
In this study, the self-made silver paste (SP) was uniformly coated on cotton yarn (CY); thereafter, a conductive path on the yarn surface was formed through a simple process of low-temperature sintering. The prepared conductive yarn was designated as sintered silver paste cotton yarn (SSP-CY). According to the sintering process, the influences of various process parameters on the electrical and mechanical properties of SSP-CY were investigated. The sintering principle of SP on the CY was discussed, and the influence of sintering process on the performance of SSP-CY strain sensing was studied. A strain sensor based on SSP-CY was investigated for monitoring the motion of human body, the subtle movements of throat caused by speaking, and the capability of humidity sensing. Furthermore, wired and radio heating, as well as electronic display operating performance were also demonstrated.
本研究将自制银浆 （SP） 均匀涂覆在棉纱 （CY） 上;此后，通过简单的低温烧结工艺在纱线表面形成导电路径。制备的导电纱被命名为烧结银浆棉纱 （SSP-CY）。根据烧结工艺，研究了各种工艺参数对 SSP-CY 电气和机械性能的影响。讨论了 SP 在 CY 上的烧结原理，并研究了烧结工艺对 SSP-CY 应变传感性能的影响。研究了一种基于 SSP-CY 的应变传感器，用于监测人体运动、说话引起的喉咙细微运动以及湿度传感能力。此外，还展示了有线和无线电加热以及电子显示器的操作性能。

2. Experimental section  2. 实验部分

2.1. Materials and chemicals
2.1. 材料和化学品

Terpineol (TE), Ethyl cellulose (EC, 99.7 %), and ethanol was obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The commercial available cotton yarn was used. Silver particles (Ag, > 99 > 99 > 99>99 %) was obtained from Zhejiang Feiyi Photoelectric Energy Technology Co Ltd. Unless otherwise stated, all chemicals are analytical reagents and do not require further purification for use.
松油醇 （TE）、乙基纤维素 （EC， 99.7 %） 和乙醇购自国药化学试剂有限公司（中国上海）。使用了市售的棉纱。银颗粒 （Ag， > 99 > 99 > 99>99 %） 购自浙江飞逸光电能源科技有限公司。除非另有说明，否则所有化学品均为分析试剂，无需进一步纯化即可使用。

2.2. Preparation of exocuticle of beetle horn shell
2.2. 甲虫角壳外角质层的制备

Anoplophora glabripennis was collected from Jiangnan University, Wuxi City, Jiangsu Province, China in July 2022. The long-horned beetle is killed with 99.5 % 99.5 % 99.5%99.5 \% ethyl acetate vapor. The long-horned beetle body length is 20 ∼ 35 mm 20 ∼ 35 mm 20∼35mm20 \sim 35 \mathrm{~mm}, width is about 5 ∼ 10 mm 5 ∼ 10 mm 5∼10mm5 \sim 10 \mathrm{~mm}. Three The long-horned
Anoplophora glabripennis 于 2022 年 7 月从中国江苏省无锡市江南大学收集。长角甲虫被 99.5 % 99.5 % 99.5%99.5 \% 乙酸乙酯蒸气杀死。长角甲虫体长 ， 20 ∼ 35 mm 20 ∼ 35 mm 20∼35mm20 \sim 35 \mathrm{~mm} 宽约 5 ∼ 10 mm 5 ∼ 10 mm 5∼10mm5 \sim 10 \mathrm{~mm} 。三 长角
beetle were selected in the experiment. After dissection, the outer horn shell is placed. Separate from the body and store in a 70 % 70 % 70%70 \% alcohol container for preservation [35,36].
甲虫在实验中被选中。解剖后，放置外角壳。与身体分开，储存在 70 % 70 % 70%70 \% 酒精容器中保存[35,36]。

2.3. Preparation of silver paste (SP) and sintered silver paste cotton yarn (SSP-CY)
2.3. 银浆（SP）和烧结银浆棉纱（SSP-CY）的制备

The silver particles was added with anhydrous ethanol, placed in a centrifuge for 10 min , then taken out and dried to remove impurities and active agents on the surface of the silver particles.
将银颗粒加入无水乙醇，置于离心机中 10 min，然后取出并干燥，以去除银颗粒表面的杂质和活性剂。
The cotton yarns were soaked in anhydrous ethanol for 30 min before sintering and then dried. The paste was put into a beaker with a ratio of EC:TE is 1: 20 and then placed on a magnetic stirrer for stirring for 30 min. The pre-treated silver particles was added, and then placed on a magnetic stirrer for stirring for 30 min to make silver paste. The silver paste was coated on the surface of the cotton yarn, standing for 5 min , and then put into the oven under 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} for 60 min . Then the SSP-CY was made.
将棉纱在无水乙醇中浸泡 30 分钟后烧结，然后干燥。将糊状物放入 EC：TE 比例为 1：20 的烧杯中，然后置于磁力搅拌器上搅拌 30 分钟。加入预处理过的银颗粒，然后置于磁力搅拌器上搅拌30min，制成银浆。将银浆涂在棉纱表面，静置 5 分钟，然后放入烘箱下 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} 放置 60 分钟。然后制作了 SSP-CY。

2.4. Characterization  2.4. 特征

The surface morphology, structure, and elemental crystallinity of SP, SSP and SSP-CY were characterized using scanning electron microscopy (SEM, Regulus 8100, Hitachi, Japan) and X-ray diffractive apparatus (XRD, D2 PHASER, Bruker, Germany). The surface and cross-section of the composite films were sprayed with gold before observation. The compositions of SP, SSP and SSP-CY were analyzed using the Fourier transform infrared spectroscopy (FTIR, Spectrum 100, Perkin Elmer, USA). Thermogravimetry (TG) and was carried out in N 2 N 2 N_(2)\mathrm{N}_{2} atmosphere using TGA2 (Mettler Toledo, China). The tensile test of yarns were characterized using yarn tensile tester (XL-2, China).
使用扫描电子显微镜 （SEM， Regulus 8100， Hitachi， Japan） 和 X 射线衍射仪 （XRD， D2 PHASER， Bruker， Germany） 表征了 SP 、 SSP 和 SSP-CY 的表面形貌、结构和元素结晶度。观察前对复合薄膜的表面和横截面进行镀金处理。使用傅里叶变换红外光谱法 （FTIR， Spectrum 100， Perkin Elmer， USA） 分析 SP 、 SSP 和 SSP-CY 的成分。热重分析法 （TG） 并在大气中使用 N 2 N 2 N_(2)\mathrm{N}_{2} TGA2（梅特勒-托利多，中国）进行。使用纱线拉伸测试仪（XL-2，中国）对纱线的拉伸试验进行了表征。
The SSP-CY@PE strain sensor was wired to the digital multimeter (34,460 A, Keysight, 3 data points/second, USA) and a desktop computer in the environment of constant temperature and humidity ( 25 ∘ C 25 ∘ C (25^(@)C:}\left(25^{\circ} \mathrm{C}\right., 60 % RH ) 60 % RH ) 60%RH)60 \% \mathrm{RH}). The digital multimeter recorded the electrical signal over time, while computer displayed and saved the data. During the humidity monitoring experience, different relative humidity environments were created by closed conical flasks containing different saturated salt solutions, where LiCl was RH 33%, NaBr was RH 57 % 57 % 57%57 \%, NaCl was RH 75%, and K 2 SO 4 K 2 SO 4 K_(2)SO_(4)\mathrm{K}_{2} \mathrm{SO}_{4} was RH 97 % RH 97 % RH97%\mathrm{RH} 97 \%, respectively.
SSP-CY@PE应变传感器在恒温恒湿 ( 25 ∘ C 25 ∘ C (25^(@)C:}\left(25^{\circ} \mathrm{C}\right. 的环境中连接到数字万用表（34,460 A，Keysight，3 个数据点/秒，美国）和台式计算机 60 % RH ) 60 % RH ) 60%RH)60 \% \mathrm{RH}) 。数字万用表记录随时间变化的电信号，而计算机显示并保存数据。在湿度监测过程中，装有不同饱和盐溶液的封闭锥形瓶创造了不同的相对湿度环境，其中 LiCl 为 RH 33%，NaBr 为 RH，NaCl 57 % 57 % 57%57 \% 为 RH 75%， K 2 SO 4 K 2 SO 4 K_(2)SO_(4)\mathrm{K}_{2} \mathrm{SO}_{4} 分别为 RH 97 % RH 97 % RH97%\mathrm{RH} 97 \% 。

3. Results and discussion
3. 结果和讨论

3.1. Materials design and fabrication.
3.1. 材料设计和制造。

The evolutionary process of nature creates the basis of matter, and numerous studies have found that biological structures adopt the method of establishing specific structures and complex interfaces to solve the conflict between strength and toughness [37]. Therefore, the design of bionic structures and interfaces based on biological structures is an effective strategy to achieve the simultaneous optimization of material strength and toughness [38]. The shell of beetle horn consists of unsmooth surface. The composition of the exocuticle is homogeneous, while the endocuticle typically contains complex fibrous structures. Its function is to resist external impact and maintain the structure of the whole body; therefore, the mechanical properties of the outer horn shell are higher than those of other parts [39]. As shown in Fig. 1a, the surface of the shell of long-horned beetle forms a compact network structure. When the long-horned beetle is subjected to external strain, its pressure and energy can be dispersed in the network gap and absorbed. The pressure and energy can also be transferred to the interior, thus reducing deformation and playing a protective role. This special high-density structure enables the long-horned beetle to better protect itself in emergencies. Inspired by this structure, and considering that this structure can be regarded as a compact conductive network, this work combined the silver particles onto the cotton yarn to enhance its
自然界的进化过程创造了物质的基础，大量研究发现，生物结构采用建立特定结构和复杂界面的方法来解决强度和韧性之间的冲突[37]。因此，基于生物结构的仿生结构和界面设计是实现材料强度和韧性同步优化的有效策略 [38]。甲虫角的外壳由不光滑的表面组成。外角质层的组成是均匀的，而内角质层通常包含复杂的纤维结构。其功能是抵抗外界冲击，维持全身结构;因此，外角壳的机械性能高于其他部件[39]。如图 1a 所示，长角甲虫的壳表面形成了一个紧凑的网络结构。当长角甲虫受到外部应变时，其压力和能量可以在网隙中分散并吸收。压力和能量也可以传递到内部，从而减少变形并起到保护作用。这种特殊的高密度结构使长角甲虫能够在紧急情况下更好地保护自己。受这种结构的启发，并考虑到这种结构可以看作是一个紧凑的导电网络，这项工作将银颗粒结合到棉纱上，以增强其
Fig. 1. SSP-CY exhibits high conductivity and strain sensing properties. (a) The Inspiration diagram of SSP-CY; (b) Schematics of preparation of SSP-CY; © increased conductivity of the SSP - CY by tensile force.
图 1.SSP-CY 具有高导电性和应变传感特性。（a） SSP-CY 的灵感图;（b） SSP-CY 的制备示意图;© 通过拉力增加 SSP - CY 的导电性。
conductive properties while maintaining the flexibility.
导电性能，同时保持柔韧性。
For the pore structure and a large number of hydrophilic groups of cotton yarn, it is benefit for the adsorption of silver paste on the surface of the yarn and the humidity sensing performance. Moreover, unlike yarns such as silk and wool yarns, cotton yarns can maintain a certain thermal stability and not be melted under the experimental temperature (Fig. S1), which makes the silver paste very stable in the process of sintering at the low temperature. We prepared silver paste and coated it on the surface of CY to make SP-CY. Sintered Silver Paste (SSP) was formed on the surface of SP-CY through low-temperature sintering process. And then the sintered silver flakes connected to each other to form a dense and stable conductive path. The resultant SSP-CY has the effect of high conductivity, high flexibility and the capability of motion detection; therefore, it is easy to be integrated into smart textile or the wearable devices. The specific production process of SSP-CY is shown in Fig. 1b. The sintering process endow the yarn with conductive property, and improves the strength of the yarn. Furthermore, the conductive yarn surface can maintain a stable conductive path under stretching (Fig. 1c, Fig. S2 and Supplementary Video 1).
对于棉纱的孔隙结构和大量的亲水基团，有利于银浆在纱线表面的吸附和湿度传感性能。而且，与丝绸和羊毛纱线等纱线不同，棉纱在实验温度下能保持一定的热稳定性而不被熔化（图S1），这使得银浆在低温烧结过程中非常稳定。我们制备了银浆并将其涂在 CY 表面以制成 SP-CY。通过低温烧结工艺在 SP-CY 表面形成烧结银浆 （SSP）。然后烧结银片相互连接，形成致密稳定的导电路径。所得的 SSP-CY 具有高导电性、高柔韧性和运动检测能力;因此，它很容易集成到智能纺织品或可穿戴设备中。SSP-CY 的具体生产工艺如图 1b 所示。烧结过程赋予纱线导电性能，提高了纱线的强度。此外，导电纱线表面在拉伸下可以保持稳定的导电路径（图 1c、图 S2 和补充视频 1）。
The resin added to most conductive silver paste is the biggest obstacle to their limited flexibility. When preparing conductive silver paste, we added non-resinous Terpineol (TE) as the solvent to ensure the dispersion of silver particles without agglomeration; Ethyecellulose (EC) was used as a bonding phase to prevent the aggregation of silver particles [ 40 , 41 ] [ 40 , 41 ] [40,41][40,41]. In addition, we also studied the effects of EC and TE ratio, silver content, sintering time and sintering temperature on the strength and conductivity of SSP-CY in silver paste. The highest strength of SSPCY is obtained as the ratio of EC:TE was 1: 20, as shown in Fig. S3a. After evaporating of the organic solvent, EC binds the silver particles together, forming a kind of mesh-like tangled structure, which enhances the strength of SSP-CY. However, as increasing the EC concentration, the distance between silver particles was also increased; therefore, the silver
添加到大多数导电银浆中的树脂是其有限柔韧性的最大障碍。在制备导电银浆时，我们添加了非树脂松油醇 （TE） 作为溶剂，以保证银颗粒的分散不结块;乙醚纤维素 （EC） 用作键合相，以防止银颗粒 [ 40 , 41 ] [ 40 , 41 ] [40,41][40,41] 聚集。此外，我们还研究了 EC 和 TE 比、银含量、烧结时间和烧结温度对银浆中 SSP-CY 强度和电导率的影响。当 EC：TE 的比例为 1：20 时，SSPCY 的强度最高，如图 S3a 所示。有机溶剂蒸发后，EC 将银颗粒结合在一起，形成一种网状缠结结构，增强了 SSP-CY 的强度。然而，随着 EC 浓度的增加，银颗粒之间的距离也增加了;因此，银
particles were hardly to form a strong connection after low-temperature sintering. As shown in Fig. S3b, it was observed that the weight gain rate from CY to SSP-CY reached about 1200 % 1200 % 1200%1200 \%, as the silver content in the paste was 87 % 87 % 87%87 \%; the electrical conductivity of SSP-CY reached the highest value of 4.08 × 10 3 S / cm 4.08 × 10 3 S / cm 4.08 xx10^(3)S//cm4.08 \times 10^{3} \mathrm{~S} / \mathrm{cm}. The electrical conductivity was calculated using formula 1 .
颗粒在低温烧结后几乎不会形成牢固的连接。如图 1 所示。S3b 中，观察到从 CY 到 SSP-CY 的增重速率达到约 1200 % 1200 % 1200%1200 \% ，因为浆料中的银含量为 87 % 87 % 87%87 \% ;SSP-CY 的电导率达到最高值 4.08 × 10 3 S / cm 4.08 × 10 3 S / cm 4.08 xx10^(3)S//cm4.08 \times 10^{3} \mathrm{~S} / \mathrm{cm} 。电导率使用公式 1 计算。
σ = 1 ρ = L R S # σ = 1 ρ = L R S # sigma=(1)/(rho)=(L)/(RS)#\sigma=\frac{1}{\rho}=\frac{L}{R S} \#
where σ σ sigma\sigma is the electrical conductivity, ρ ρ rho\rho is the electrical resistivity, R R RR is the resistance of the measured length, L L LL is the measured length of yarn resistance measurement, S S SS is the cross-sectional area of the yarn.
式中 σ σ sigma\sigma 是电导率， ρ ρ rho\rho 是电阻率， R R RR 是被测长度的电阻， L L LL 是被测纱线电阻的长度测量， S S SS 是纱线的横截面积。
In addition, when the silver content was low at 80 % 80 % 80%80 \%, the electrical conductivity of SSP-CY is about 1.0 × 10 3 S / cm 1.0 × 10 3 S / cm 1.0 xx10^(3)S//cm1.0 \times 10^{3} \mathrm{~S} / \mathrm{cm}. As the content of silver reaches 89 % 89 % 89%89 \%, the excessive content of silver will lead to agglomeration of silver particles. As a result, the solvent proportion is low and the silver powders can hardly fully dispersed. The low adhesion content of silver paste resulted in the decrease of electrical conductivity. As the sintering process over 60 min , it was observed that at different sintering temperatures the conductivity and weight gain rate of SSP-CY had a slight change (Fig. S3c). The results demonstrated that the silver particles have not fully sintered before 60 min , and hard to form a complete conductive path. In addition, it is also observed that the conductivity of SSP-CY increased with the increase of sintering temperature, but the conductivity and weight gain rate of SSP-CY did not change significantly (Fig. S3d), after the sintering temperature higher than 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C}. Therefore, the following experimental parameter was set as EC: TE mixture with the weight ratio of 1 : 20 1 : 20 1:201: 20, the silver content in the paste of 87 % 87 % 87%87 \%, and the sintering process of 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} for 60 min .
此外，当 的 80 % 80 % 80%80 \% 银含量较低时，SSP-CY 的电导率约为 1.0 × 10 3 S / cm 1.0 × 10 3 S / cm 1.0 xx10^(3)S//cm1.0 \times 10^{3} \mathrm{~S} / \mathrm{cm} 。随着银的含量达到 89 % 89 % 89%89 \% ，银的超标会导致银颗粒团聚。因此，溶剂比例低，银粉几乎不能完全分散。银浆的低粘附率导致导电性降低。随着烧结过程超过 60 分钟，观察到在不同的烧结温度下，SSP-CY 的电导率和增重率略有变化（图 S3c）。结果表明，银颗粒在 60 min 之前尚未完全烧结，并且难以形成完整的导电路径。此外，还观察到 SSP-CY 的电导率随着烧结温度的升高而增加，但在烧结温度高于 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} 后，SSP-CY 的电导率和增重率没有显着变化（图 S3d）。因此，将以下实验参数设置为EC：TE混合物重量比为， 1 : 20 1 : 20 1:201: 20 浆料中银含量为 87 % 87 % 87%87 \% ，烧结过程 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} 为60 min。
    • Corresponding author.  通讯作者。
    E-mail address: lixiaoqiang@jiangnan.edu.cn (X. Li).
    电子邮件地址：lixiaoqiang@jiangnan.edu.cn （X. Li）。