醛-亚胺-壳聚糖水凝胶的构筑及性能研究进展

动态亚胺键（又称席夫碱键）具有pH响应性、可逆性和生物活性等,因此,亚胺键交联构筑的水凝胶可能被赋予许多新的功能。壳聚糖是自然界中唯一的碱性多糖,分子链上丰富的氨基为醛-亚胺-壳聚糖（CSB）水凝胶的构筑提供了可能。近年来,CSB水凝胶的构筑和应用受到关注,其中,醛类交联分子的结构和交联点的设计成为研究热点之一。该文按照醛类交联分子的结构特点,对CSB水凝胶的构筑方法、机理以及自愈合性能、药物缓释性能、抗菌性能、荧光性能和导电性能等进行了综述,为构筑多功能壳聚糖水凝胶提供理论指导。设计合成生物相容性好、多功能醛类交联剂;提高CSB水凝胶的力学性能、自愈合性能和刺激响应性能,是CSB水凝胶的重要研究方向。     

PAAS/PVA/Zn0.2Fe2.8O4磁性复合水凝胶的合成及其性能研究

以化学共沉淀法制备了在水中分散性良好的柠檬酸包覆的掺锌纳米四氧化三铁（Zn_0.2Fe_2.8O₄,ZFO）粒子,并用X射线衍射仪、透射电子显微镜及综合物理特性测试仪进行测试。结果表明,该纳米粒子粒径为3~8 nm,粒径较为均一且饱和磁化强度可达60 emu/g,再通过在水相中引发丙烯酸钠聚合交联并结合冷冻解冻交联制得聚乙烯醇/聚丙烯酸钠/ZFO（PVA/PAAS/ZFO）互穿网络水凝胶;纳米ZFO粒子的引入可同时使水凝胶的拉伸强度提高约1.5倍; ZFO粒子的加入对水凝胶的热稳定性有一定的提高;纳米ZFO粒子的引入可加快水凝胶的电响应的速率和程度。     

醛-亚胺-壳聚糖水凝胶的构筑及性能研究进展

动态亚胺键(又称席夫碱键)具有pH响应性、可逆性和生物活性等,因此,亚胺键交联构筑的水凝胶可能被赋予许多新的功能.壳聚糖是自然界中唯一的碱性多糖,分子链上丰富的氨基为醛-亚胺-壳聚糖(CSB)水凝胶的构筑提供了可能.近年来,CSB水凝胶的构筑和应用受到关注,其中,醛类交联分子的结构和交联点的设计成为研究热点之一.该文按照醛类交联分子的结构特点,对CSB水凝胶的构筑方法、机理以及自愈合性能、药物缓释性能、抗菌性能、荧光性能和导电性能等进行了综述.指出设计合成生物相容性好、多功能醛类交联剂及提高CSB水凝胶的力学性能、自愈合性能和刺激响应性能是CSB水凝胶的重要研究方向.     

自愈水凝胶的设计原理及应用

自愈水凝胶是一种在遭到外界破坏损伤后可自行修复其结构和功能的智能水凝胶。在保留传统水凝胶吸水保水性质的基础上,自愈水凝胶仍具有可自修复、安全性高、耐疲劳、使用寿命长等优势。本文综述了近年来基于物理、化学交联和多重作用机理结合型自愈水凝胶及其在可穿戴电子产品、3D打印、生物医药、石油化工领域的部分应用。物理交联包含氢键、疏水相互作用、主客体相互作用等非共价键交联,化学交联包含酰腙键、亚胺键、二硫键等共价键交联,多重作用机理交联是将两种以及两种以上的物理、化学交联同时引入。在上述研究基础上,指出了目前自愈水凝胶存在制备方法烦琐、功能单一、无法响应多重刺激以及缺乏多方位解析自愈合机制等问题。因此,未来自愈水凝胶的研发重点应侧重在多机制、多功能型自愈水凝胶的研发,从多角度、多学科交融探索水凝胶自愈合机制,促进其在多个新兴领域的应用。     

基于Fe3+-DA-APS自催化体系的Fe3O4/PAA水凝胶的制备及性能研究

以Fe₃O₄纳米粒子为磁性组分,基于AA(丙烯酸)与部分Fe₃O₄反应产生的Fe³⁺、多巴胺(DA)构建双重自催化过硫酸铵(APS)的自由基聚合体系,在低温下制备了Fe₃O₄/聚丙烯酸(PAA)水凝胶,并对其进行表征。研究结果表明：Fe₃O₄/PAA水凝胶具有良好的力学性能,断裂伸长率、拉伸强度分别为900%、251.1 kPa;同时,其可较好粘附不同基材,在钢材上粘附-剥离循环20次后粘附强度仍稳定在30.7 kPa左右;此外,其还可感应极小形变,并在166 ms内快速响应。该Fe₃O₄/PAA水凝胶综合性能良好,具备应用于柔性传感器等领域的潜力。     

羧基化填料对聚乙烯醇/纳米纤维素水凝胶力学、导电和传感性能的影响

利用羧基化碳纳米管（CNT）和纳米纤维素微晶（CNC）与聚乙烯醇/纳米纤维素（PVA/CNF）中形成氢键构建致密的交联网络,并对水凝胶进行增强改性。结果表明,加入3 %（质量分数,下同）的CNT可以使水凝胶的拉伸强度由50 kPa提高至120 kPa,而加入3 %的CNC能够同时提高水凝胶的拉伸强度和断裂伸长率;加入CNT后能够在水凝胶中构建导电逾渗网络,结合溶剂中的离子导电使得水凝胶的电阻率显著下降;使用PVA/CNF?CNT3水凝胶制作应变传感器,能够实现拉伸、压缩和弯曲等多种应变的快速、准确传感响应。     

自愈合水凝胶的研究进展

自愈合水凝胶作为一种新型功能凝胶材料，目前在现代科学研究中展现了十分突出的应用前景。本文对水凝胶的自愈合机理进行了描述和分类。非共价交联水凝胶与共价交联水凝胶都有着不同的自愈合性质。非共价交联水凝胶主要以氢键、疏水相互作用以及离子键来实现其自愈合的性质，而共价交联水凝胶的自愈性主要依靠动态共价键以及金属配位键。本文还描述了近些年来自愈合水凝胶在生物医疗、3D打印、可穿戴电子产品以及离子吸附的部分应用。最后，对自愈合水凝胶未来的发展作了展望。     

应变响应抗冻保水海藻酸钙/聚乙烯醇导电水凝胶

针对传统水凝胶耐候性差及易失去柔性等问题，以海藻酸钠(Sodium Alginate, SA)、聚乙烯醇(Polyvinyl Alcohol, PVA)为基质，单宁酸(Tannic Acid, TA)和氯化钙(Calcium Chloride, CaCl₂)为交联剂，甘油(Glycerol, GL)和水为溶剂，制备了多重交联海藻酸钙(Calcium Alginate, CA)/聚乙烯醇(CA/PVA)水凝胶。研究显示该水凝胶具有优异的力学性能、抗冻保水性及导电性。其拉伸断裂伸长率可达～808%;常温电导率达0.32 S/m;-60℃时仍不冻结，且较宽温度范围内具备良好导电性能；25℃、相对湿度60%的环境中放置一周仅失水35%。该水凝胶应变传感性良好，可作为柔性传感器稳定监测人体细微动作。     

基于铂、钯负载的MoS2纳米片构建生物传感器及应用

制备了Pt和Pd纳米颗粒修饰的单层MoS₂纳米片（Pt-Pd/MoS₂）,通过扫描电镜（SEM）、透射电镜（TEM）和X射线光电子能谱（XPS）对Pt-Pd/MoS₂外部形貌、内部结构和组成进行表征分析,并基于Pt-Pd/MoS₂修饰玻碳电极,并于表面固定乙酰胆碱酯酶（AChE）,制备AChE生物传感器。对比了Pt和Pd双金属纳米颗粒、商品化Pt/C及Pt-Pd/MoS₂的电化学性能,结果发现,Pt-Pd/MoS₂的电化学性能明显优于其他两种。测定电极表面酶催化反应的动力学参数K_m为883μmol/L;以马拉硫磷和甲基对硫磷为代表,考察制备电极的检测性能以及制备电极对有机磷农药的检测性能,马拉硫磷的检测范围是1×10^-14～1×10^-5mol/L,检测限为4.69×10^-14mol/L;甲基对硫磷的检测范围是1×10^-15～1×10^-5mol/L,检测限为5.23×10^-15mol/L（S/N=3）;并应用于真实样品检测OPs的回收率为91.4%～103%,显示出良好的回收率和准确性,可应用于实际样品的分析。Pt-Pd/MoS₂为二维纳米材料构建高效生物传感器提供了新思路。     

自愈合凝胶在柔性传感器中的应用研究进展

自愈合凝胶具有优异的机械性能、良好的生物相容性和延长材料使用寿命功能等特性,已广泛应用在电子皮肤、柔性机器人、可穿戴设备等方面。凝胶基质结构的可调性和导电材料选择的多样性也为制备具有不同功能的柔性传感器提供了可能。该文根据交联方式、功能性类型、愈合方式和胶凝剂相对分子质量大小4种分类方式将自愈合凝胶进行了分类,并详细介绍了各种自愈合凝胶的成胶机制和性能特点。综述了自愈合凝胶在柔性传感器中力学、光电和生物方面的国内外研究现状。最后,讨论了该研究领域仍存在的问题,并对其未来发展前景及方向进行了简要展望。     

A self-healing and conductive ionic hydrogel based on polysaccharides for flexible sensors

In this study, we proposed a self-healing conductive hydrogel based on polysaccharides and Li⁺ to serve as flexible sensors. At first, the oxidized sodium alginate(OSA) was obtained through the oxidation reaction of sodium alginate(SA). Then OSA, carboxymethyl chitosan(CMC), and agarose(AGO) were dissolved in Li Cl solution, respectively. Finally, the hydrogel was obtained through heating, mixing, and cooling processes. Because of the Schiff base structure and hydrogen bonding, the hy...     

Double Network Hydrogel Sensors with High Sensitivity in Large Strain Range

Owing to their preferable flexibility and facilitation to integrate with various apparel products, flexible sensors with high sensitivity are highly favored in the fields of environmental monitoring, health diagnosis, and wearable electronics. However, great challenges still remain in integrating high sensitivity with wide sensing range in one single flexible strain sensor. Herein, a new stretchable conductive gel-based sensor exhibiting remarkable properties regarding stretchability and sensitivity is developed via improving the ionic conductivity of the PVA/P(AM-AANa) double network hydrogel. Specifically, the strain sensor developed exhibits an excellent elongation of 549%, good fatigue resistance, and recovery performance. Simultaneously, the hydrogel strain sensor shows a high conductivity of 25 mS cm⁻¹, fast response time of 360 ms, and a linear response (gauge factor = 4.75) to external strain (≈400%), which endow the sensor with accurate and reliable capacities to detect various human movements. Integrating the merits of flexibility, environment friendliness, and high sensitivity, the conductive gel-based sensor has promising application prospects in human–machine interfaces, touchpads, biosensors, electronic skin, wearable electronic devices, and so on.     

Highly Stretchable,Tough, and Conductive Ag@Cu Nanocomposite Hydrogels for Flexible Wearable Sensors and Bionic Electronic Skins

Flexible conductive materials and flexible electronic devices are driving the development of the next generation of cutting-edge wearable electronics. However, the existing hydrogel-based flexible conductive materials have limited tensile capacity, low toughness, and poor anti-fatigue performance, resulting in narrow sensing area and insufficient durability. In this paper, a conductive nanocomposite hydrogel with high ductility, toughness, and fatigue resistance is prepared by combining silver coated copper (Ag@Cu) nanoparticles with gelatin followed by one-step immersion in sodium sulfate (Na₂SO₄) solution. The salting-out of gelatin in Na₂SO₄ solution greatly improve the mechanical properties of this gelatin-based hydrogel. The uniform distribution of Ag@Cu nanoparticles inside the whole hydrogel endow the composite hydrogel with excellent electrical conductivity (1.35 S m⁻¹). In addition, it displayed high and stable tensile strain sensitivity over a wide strain range (gauge factor = 2.08). Therefore, the Ag@Cu-Gel hydrogel is sensitive and stable enough to be successfully utilized as flexible wearable sensor for detecting human motion signals in real time, such as bending of human joints, swallowing, and throat vocalization. Furthermore, this hydrogel is also suitable for application as electronic skin for bionic robots. The above results demonstrate the promising application of Ag@Cu-Gel hydrogel for wearable electronics.     

A highly elastic and sensitive sensor based on GSP/HPAM composited hydrogel

Development of conductive hydrogels to mimic the structures and properties of human skin has attracted enormous scientific interests. However, applications of such materials are often restricted by their poor mechanics and moderate sensitivities. Herein, a highly-stretchable, self-healing, and conductive hydrogel, comprised of grape seed extracted polymer and hydrophobically associated polyacrylamide (GSP-HPAM), was fabricated by simple mixing and in-situ polymerization. Compared with the single HPAM gels, the rigid GSP polymer could form sufficient hydrogen bonds and ionic interactions, which endowed the gel with effective energy dissipation mechanism and greatly improved the uniformity of network. As a result, the GSP-HPAM gel exhibited enhanced mechanics, that is, the tensile strength, strain, and compression stress of GSP-HPAM hydrogel were 0.7 MPa, 3000% and 28.3 MPa, respectively. Furthermore, the gel demonstrated linear strain-dependant conductivity between 0% and 1000% with gauge factor around 3.43, superior to most hydrogel-based strain sensors. In addition, the gel was able to monitor human body motion, such as, finger bending and pulse rate. This multiple functional gel might find potential applications in artificial skin, soft robotics, and wearable devices.     

Bacterial Cellulose Reinforced Polyaniline Electroconductive Hydrogel with Multiple Weak H-Bonds as Flexible and Sensitive Strain Sensor

Hydrogel, as a promising soft material, possesses many functional advantages such as stretchability, viscoelasticity, and biocompatibility. An advanced electronic platform for strain sensor is constructed by modifying hydrogels with various doping techniques. Herein, a novel flexible conductive hydrogel is synthesized by combination of bacterial cellulose/sodium alginate/polyacrylamide with the polyaniline (BSP-PANI) through multiple intermolecular interactions. In the obtained BSP-PANI hydrogel system, the incorporated BC serves the function of mechanically toughening and the formation of polyaniline conducting network endows the hydrogels electrical conductivity. The assembled hydrogel strain sensor can detect electrical response under different applied strains (1–200%) and monitor human motion in real time. Therefore, it is believed that the BSP-PANI hydrogel prepared by the feasible synergetic strategy proposed in this work has greatly diversified application in smart epidermal sensors and artificial intelligence devices.     

异质结构碳材料的金属空气电池应用研究进展

金属空气电池在可穿戴电子产品和能源储存领域中具有巨大的应用潜力,然而稳定性差和能量效率低的问题限制其性能的进一步提高。电化学氧还原反应（ORR）和氧析出反应（OER）对于金属空气电池的性能起着至关重要的作用。发展催化活性高、稳定性好的空气电极催化剂是未来的研究趋势。碳材料因具有导电性优异、结构多样等优势已被广泛用作金属空气电池的导电骨架支撑材料和电催化材料,成为研究的热点。对非金属原子掺杂碳材料、过渡金属及其衍生物掺杂碳材料以及单原子催化剂作为单功能或双功能催化剂的研究进行综述,着重介绍了其在金属空气电池中的应用,对空气电极催化剂存在的问题进行总结,并对未来的发展方向进行展望。     

Anisotropic strain sensors to realize skin-comparable performances

Conductive hydrogels (CHs) are promising candidates for wearable devices. However, it remains challenging for traditional CHs to realize a combination of self-adhesive and skin-comparable performances. Herein, a stretch-induced orientation strategy was demonstrated to achieve this goal. The hydrogel was fabricated from poly(vinyl alcohol), aluminum sulfate, tannin acid, and deionized water, which exhibited skin-comparable elastic modulus (26.3 kPa), stretchability (180%), and water content (87.6%). Meanwhile, it had anisotropic properties. For instance, the mechanical and anisotropy ratios between parallel and orthogonal directions were 1.77 and 2.02, respectively. Furthermore, the presence of free ions within regular conductive channels imparted stable conductivity (gauge factor of 2.2 within 200% strains), fast response (0.2 s), and low detect limit (a strain of 0.2%). Additionally, the existence of catechol groups from tannin acid enabled self-adhesion ability (adhesion strength of 73.9 kPa). All of these merits show promising potential in wearable devices and electronic skins.     

Effects of crosslinking reaction and extension strain on the electrical properties of silicone rubber/carbon nanofiller composites

Stretchable conductive silicone rubber (SR) composites are important in wearable electronic devices and the crosslinking of SR composites is necessary for their applications. But the effect of the crosslinking reaction on the electrical conductivity of SR composites is rarely reported. In this article, the effect of crosslinking reaction on the electrical conductivity of SR composites filled with conductive carbon black, carbon nanotubes, and graphene are studied. The crosslink density of SR composites increases with increasing curing time, but the electrical conductivity decreases sharply at the early stage of crosslinking, especially for SR/conductive carbon black composite, which is ascribed to the reaggregation of conductive nanofillers in SR during the crosslinking process. The elastic modulus of the three SR composites gradually increases while the elongation at break decreases with increasing curing time, and the SR/carbon black composite shows ultra-high elongation at break (1578%). In addition, SR/graphene composite is more sensitive to the extension strain than SR/carbon black and SR/carbon nanotubes composites, and its gauge factor is 414 at the strain ranges of 3–25%. This research work brings a new method to optimize the crosslinking structure of conductive SR composites.     

Quickly self-healing hydrogel at room temperature with high conductivity synthesized through simple free radical polymerization

The use of conductive self-healing hydrogels in electronic devices not only reduces replacement and maintenance costs but also prolongs their lifetime. Therefore, developing hydrogels with autonomous self-healing properties and electronic conductivity is vital for the advancement of emerging fields, such as conductors, semiconductors, sensors, artificial skin, and electrodes and solar cells. However, it remains a challenge to fabricate a hydrogel with high conductivity that can be healed quickly at room temperature without any external stimulus. In this work, we report an effective and simple free radical polymerization approach to synthesizing a hydrogel using modified rGO and acrylate monomers containing abundant ion groups. The hydrogel exhibits excellent electronic conductivity, extremely fast electronic self-healing ability, and excellent repeatable restoration performance at 25 °C. The conductivity of the hydrogel reaches 27.2 S/m, the hydrogel recovers its original shape, and scoring scratched on the surface totally disappears after holding at 25 °C for 40 s. This conductive, room-temperature self-healing hydrogel takes unique advantage of supramolecular chemistry and polymer nanoscience and has potential applications in various fields such as self-healing electronics, artificial skin, soft robotics, biomimetic prostheses, and energy storage. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47379.     

Magnetic nanocomposite hydrogel with ultra-stretchable as strain sensors for monitoring human motion and the change of magnetic field

In recent years, the smart hydrogels have gained much concern in the field of research specially related to flexible strain sensors because they exhibit many types of smart interactions that can be useful in wearable devices. However, the conventional hydrogels have poor electrical conductivity that affect the performance of the sensors, so it remains a challenge to achieve noncontact signal monitoring (e.g., for the detection of magnetic field changes). In this study, an ultra-stretchable and magnetically responsive conductive hydrogel was fabricated by adding magnetic ferric tetroxide@polypyrrole composite nanoparticles (Fe₃O₄@PPy NPs) to polyacrylamide (PAm). The nanoparticles were easily agglomerated and improved the compatibility of PPy and hydrogel. The obtained PAm/Fe₃O₄@PPy hydrogel showed an ultra-stretchability of (961%), a low elastic modulus of (87.8 kPa), and an excellent toughness of (1010.5 kJ m⁻³). Moreover, PAm/Fe₃O₄@PPy hydrogel also exhibited a high electrical conductivity of 0.34 S m⁻¹, and the PAm/Fe₃O₄@PPy hydrogel sensor could detect human motions (such as bending of finger, bending of wrist) and muscle micromotion (such as pronouncing). In addition, it can also monitor the change in magnitude of magnetic field.