抗冻水凝胶的制备及其在柔性电子领域的应用

水凝胶具有优异的柔韧性、离子运输性和可调的机械性,在柔性电子领域具有广阔的应用前景,然而,水凝胶电子器件在严寒气候下容易冻结失效,严重限制了其在低温环境下的应用潜力,通过向水凝胶中引入低温防护剂可以赋予水凝胶抗冻性能,拓宽水凝胶电子器件的工作温度。该文从溶质离子、离子液体、有机溶剂以及抗冻蛋白改性水凝胶4个方面,综述了近年来抗冻水凝胶的制备方法和抗冻机理,阐述了抗冻水凝胶在超级电容器、传感器和电池等柔性电子领域的应用进展,归纳了抗冻水凝胶电子材料面临的问题与挑战,并展望了抗冻水凝胶电子材料的发展趋势,指出以天然可再生资源为原料开发具有优异机械性能、电化学性能、生物无毒性、生物相容性和生物可降解的抗冻水凝胶成为下一步研究重点,同时设计优化柔性电子装置、提高器件安全可靠性和输出稳定性也将成为重要的研究方向之一。抗冻水凝胶的制备及其应用研究将促进柔性电子功能材料领域的快速发展。     

基于液态金属的水凝胶应变传感器

近年来，基于导电水凝胶的应变传感器发展迅速，液态金属作为一种新型导电材料由于具有高导电性、良好的生物相容性、柔性和可变性，在导电水凝胶传感器的制备和应用中受到了越来越多的关注。本文介绍了液态金属以分散的液滴和连续的流体两种形式在导电水凝胶制备中的应用，及所制备的基于液态金属导电水凝胶传感器的性能，最后，对基于液态金属的水凝胶传感器的应用前景进行了展望。     

可拉伸的PVA/CNC/NaCl导电水凝胶制备及柔性传感应用

基于柔性电子领域的发展需求,水凝胶因其可拉伸性和较好的生物相容性被认为具有很大的应用前景。以聚乙烯醇(Polyvinyl alcohol, PVA)作为基体,加入纤维素纳米晶体(Cellulose nanocrystal, CNC)作为增强填料,氯化钠(NaCl)作为电解质以提高水凝胶的电导率,采用30 kGy的γ辐照制备得到的水凝胶具有良好的力学性能(断裂伸长率421%、最大拉伸应力为68.9 kPa)和导电性能(电导率2.85 S/m),将PVA/CNC/NaCl水凝胶作为应变传感器,可应用于手指弯曲、手腕弯曲、手肘弯曲等人体部位运动状况检测,稳定性良好,并表现出较好的灵敏度,验证了该水凝胶的实用性并为其后续应用奠定基础。     

生物医用高强度水凝胶的研究进展

水凝胶是一种高含水量的三维网状聚合物,广泛应用于各个领域,但力学性能较差的特点限制了其在生物医用领域的应用。因此,如何提高水凝胶的力学强度成为国内外专家学者研究的重点。本文主要介绍了几种新型高强度水凝胶的合成及研究进展,包括滑动水凝胶、双网络水凝胶、复合水凝胶以及其它水凝胶,详细分析了影响这些水凝胶力学性能的因素。指出研制具有生物相容性、可生物降解、可注射、可负载活性因子并且具备良好的力学性能水凝胶是今后的研究方向。     

导电水凝胶的研究进展

导电水凝胶作为一种新型功能凝胶材料,受到了广大科研工作者的关注。本文总结了导电水凝胶的类型,分为聚电解质导电水凝胶、酸掺杂导电水凝胶、无机物填充导电水凝胶和导电高分子基导电水凝胶四大类。并综述其在柔性可穿戴电子产品、能源存储、能源转换及药物的可控释放等方面具有的应用前景。最后,对未来导电水凝胶的发展做了展望。     

面向柔性超级电容器的功能水凝胶材料的研究进展

功能水凝胶作为一种三维高分子网络结构的软湿材料,具有可灵活调控的功能特性,为设计和构建高性能柔性超级电容器提供了理想的材料。本文综述了近年来面向柔性超级电容器领域的功能水凝胶材料的研究进展,重点分类介绍了面向电化学双层电容器和赝电容器的功能水凝胶材料的设计构建和性能强化。探讨了通过水凝胶电解质及电极材料的组成结构设计和性能调控来提升超级电容器的电化学性能和力学性能的策略。同时,探讨了水凝胶电解质及电极材料的组成结构设计和性能调控在实现其自愈合、高耐寒等多样化功能特性方面的重要作用。最后,对功能水凝胶材料柔性超级电容器在高储能、高柔性、高保水、自愈合、高耐寒、绿色可降解等方面的未来发展进行了展望。     

双网络水凝胶的研究进展

双网络水凝胶在保持高吸水性等性能的基础上改善了传统水凝胶机械性能差、不稳定等缺点。重点介绍了双网络水凝胶及其在组织工程、伤口敷料、离子吸附、农林业等方面的应用。当在组织工程、导电和伤口敷料等医学领域应用时,水凝胶的生物相容性及力学性能成为研究重点;当应用在林业和吸附染料、离子方面时,水凝胶的溶胀性能较为重要。     

一种具有自愈合性能的多孔水凝胶的研制

基于双网络结构的机制,通过在聚谷氨酸的侧基上接枝多巴胺构建相邻高分子链段间的弱键相互作用,再将接枝产物与聚赖氨酸通过酰胺反应制备了具有一定强度和良好自愈合性能的水凝胶。通过红外光谱及核磁共振氢谱对制备过程中的酰胺反应以及用扫描电镜对水凝胶多孔结构进行了表征;通过力学测试和黏弹性测试对水凝胶的力学性能、黏弹性及自愈合性能进行了表征;借助L929细胞共培养考察材料的生物相容性。结果表明制得的水凝胶具有一定的力学强度以及较好的孔隙结构、自愈合性能和生物相容性。     

高分子水凝胶材料在生物医药领域的应用

水凝胶属于典型三维网络材料,主要是由高分子聚合物构成。天然高聚物以及相关衍生材料制备的水凝胶具有生物可降解性、相容性、对环境无污染等特点,在生物医药领域获得了颇为广泛的运用。文章综述了高分子水凝胶制备的方法,介绍了其在生物医药领域的相关应用,以期为其在医学领域的开发和研究提供相应的参考。     

功能性明胶基水凝胶的分类及研究进展

明胶基水凝胶作为一类具有三维网络结构的天然高分子软物质材料,因具有良好的生物相容性、生物可降解性以及生物安全性,且含水量高、结构和性能与细胞外基质相似而受到研究者的广泛关注.该文概述了明胶基水凝胶的结构与性质,并按功能性将明胶基水凝胶进行分类,重点阐述了自修复型、抗菌型、刺激响应型、导电型以及抗冻型明胶基水凝胶的特点、...     

抗冻水凝胶的制备及其在柔性电子领域的应用

水凝胶具有优异的柔韧性、离子运输性和可调的机械性,在柔性电子领域具有广阔的应用前景.然而,水凝胶电子器件在严寒气候下容易冻结失效,严重限制了其在低温环境下的应用潜力.向水凝胶中引入低温防护剂可以赋予水凝胶抗冻性能,拓宽水凝胶电子器件的工作温度.该文从溶质离子、离子液体、有机溶剂以及抗冻蛋白改性水凝胶4个方面,综述了近年...     

Highly Stretchable,Fast Self‐Healing,Responsive Conductive Hydrogels for Supercapacitor Electrode and Motion Sensor

Conductive hydrogels as potential soft materials have attracted tremendous attention in wearable electronic devices. Nonetheless, manufacturing intelligent materials that integrate mouldability, stretchability, responsive ability, fast self‐healing ability, as well as mechanical and electrochemical properties is still a challenge. Here, multifunctional conductive hydrogels composed of poly(vinyl alcohol) (PVA) and polypyrrole (PPy) nanotube are prepared using borax as cross‐linker. The existence of multicomplexation, entangled PVA chains, and interconnected PPy nanotubes, as well as extensive hydrogen bonding results in the fabrication of hierarchical network of PVA‐PPy hydrogels. PVA‐PPy hydrogels exhibit high stretchability (more than 1000%), multiresponsiveness, low density (0.95 g cm^?3), high water content (96%), and 15 s self‐healing features. Furthermore, the self‐healing supercapacitor electrode and motion sensor based on PVA‐PPy hydrogels demonstrate ideal performances. This facile strategy in this work would be promising to construct an excellent multifunctional soft material for various flexible electrode and biosensor.     

Polyaniline/Poly(acrylamide‐co‐sodium acrylate) Porous Conductive Hydrogels with High Stretchability by Freeze‐Thaw‐Shrink Treatment for Flexible Electrodes

With the development of alternatives to traditional fossil energy and the rise of wearable technology, flexible energy storage devices have attracted great attention. In this paper, a polyaniline/poly(acrylamide‐sodium acrylate copolymer) hydrogel (PASH) with high flexibility and excellent electrochemical properties for flexible electrodes is fabricated by freeze‐thaw‐shrink treatment of a highly water‐absorptive hydrogel, together with in‐situ polymerization of aniline at a low aniline concentration (0.1 mol L^?1). The PASH exhibits a conductivity of 4.05 S m^?1 and an elongation at break of 1245%. The freeze‐thaw‐shrink treatment greatly improves the electrochemical performance and stability of the conductive PASH. The area specific capacitance of PASH reaches 849 mF cm^?2 and the capacitance maintains 89% after 1000 galvanostatic charge–discharge cycles. All the raw materials are conventional industrialized materials and no additional templating agent is needed during the entire synthesis process. This study provides a cost‐efficient approach for the fabrication of conductive polymer hydrogels, which has a broad application prospect in flexible energy storage electronic 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.     

MXene Reinforced PAA/PEDOT:PSS/MXene Conductive Hydrogel for Highly Sensitive Strain Sensors

Conductive hydrogel has a vital application prospect in flexible electronic fields such as electronic skin and force sensors. Developing conductive hydrogel with significant toughness and high sensitivity is urgently needed for application research. In this work, a strong and sensitive strain sensor based on conductive hydrogel is demonstrated by introducing MXene (Ti3C2Tx) into the micelle crosslinked polyacrylic acid (PAA)/poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) hydrogel network. The functional polymer micelle crosslinkers can dissipate external stress by deformation, endowing the hydrogel with high strength. The combination of MXene both improves the polymer network structure and the conductive pathways, further enhancing the mechanical properties and sensing performance. Resultantly, the flexible strain sensor base on PAA/PEDOT:PSS/MXene conductive hydrogel exhibits excellent sensing performance with a high gauge factor of 20.86, a large strain detection range of 1000%, as well as good adhesion on different interfaces. Thus, it can be used to monitor various movements of the human body and identify all kinds of handwriting, showing great potential into wearable electronics.     

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.     

Changes in the Mechanical Properties of Alginate-Gelatin Hydrogels with the Addition of Pygeum africanum with Potential Application in Urology

New hydrogel materials developed to improve soft tissue healing are an alternative for medical applications, such as tissue regeneration or enhancing the biotolerance effect in the tissue-implant–body fluid system. The biggest advantages of hydrogel materials are the presence of a large amount of water and a polymeric structure that corresponds to the extracellular matrix, which allows to create healing conditions similar to physiological ones. The present work deals with the change in mechanical properties of sodium alginate mixed with gelatin containing Pygeum africanum. The work primarily concentrates on the evaluation of the mechanical properties of the hydrogel materials produced by the sol–gel method. The antimicrobial activity of the hydrogels was investigated based on the population growth dynamics of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, as well as the degree of degradation after contact with urine using an innovative method with a urine flow simulation stand. On the basis of mechanical tests, it was found that sodium alginate-based hydrogels with gelatin showed weaker mechanical properties than without the additive. In addition, gelatin accelerates the degradation process of the produced hydrogel materials. Antimicrobial studies have shown that the presence of African plum bark extract in the hydrogel enhances the inhibitory effect on Gram-positive and Gram-negative bacteria. The research topic was considered due to the increased demand from patients for medical devices to promote healing of urethral epithelial injuries in order to prevent the formation of urethral strictures.     

Application of minimally invasive injectable conductive hydrogels as stimulating scaffolds for myocardial tissue engineering

So far, several methods for myocardial tissue engineering have been developed to regenerate myocardium and even create contractile heart muscles. Among these approaches, hydrogel based methods have attracted much attention due to their ability to mimic the architecture of native extracellular matrix. Injectable hydrogels are a specific class of hydrogels which can be formed in situ by physical and/or chemical crosslinking. Generally, using these hydrogels is more advantageous because they are minimally (less) invasive in comparison with open surgery. Moreover, with respect to the fact that ‘myocardium is a conductive tissue’, utilization of conductive polymers for myocardial tissue engineering has demonstrated promising results. Both the injectable hydrogels and conductive polymers have some merits and demerits, but studies show that using a combination of them has prominently enhanced regeneration of the myocardium. In this review, the focus is on injectable hydrogels, conductive polymers and injectable conductive hydrogels for myocardial tissue engineering. © 2018 Society of Chemical Industry     

Electrically conductive and mechanically tough graphene nanocomposite hydrogels with self‐oscillating performance

Conventional hydrogels are extremely brittle, fragile and poorly conductive, which limits their applications in a variety of aspects. In this study, we fabricated a novel kind of nanocomposite self‐oscillating hydrogel poly(AA‐co‐Fe(phen)₃)/PVA/RGO with high conductivity and good mechanical strength by dispersing reduced graphene oxide (RGO). Due to the synergetic effect of RGO dispersed in the hydrogels or dry gels and Fe metal which is the reduction product of the Fe(phen)₃ moiety by RGO, the hydrogels have a high conductivity of 18.2 S m^?1 with 0.67 wt% RGO content. The dispersed RGO in the hydrogels combined with the network structure by means of hydrogen bonding, π–π stacking and electrostatic interaction and was demonstrated to enhance the mechanical properties of the hydrogels. The elastic modulus achieves 65.2 kPa (1020% of the tensile strength) and 236.4 kPa (with 70% compression), respectively. In addition, the prepared hydrogels exhibit a self‐oscillating behavior in a Belousov–Zhabotinsky solution free of catalyst. These results can be broadly applied in the future in the development of an autonomous on–off switching, flexible/stretchable, graphene‐based soft electronic device. © 2019 Society of Chemical Industry