纳米纤维素基材料在柔性电子器件中的应用

目的 由于纳米纤维素基材料良好的柔韧性、热力学性能和高透明度,近年来在柔性电子产品中引起越来越多的关注。通过综述该领域的研究进展,将有助于研究人员更高效地开展研究。方法 综述3类纳米纤维素的制备方法及将纳米纤维素基材料应用在柔性电子产品中的研究进展。分别阐述纳米纤维素基材料应用于器件柔性衬底及绝缘材料的研究实例,并讨论纳米纤维素在各种应用方向中的优势以及存在的问题,最后对材料的未来应用前景进行展望。结论 纳米纤维素是天然纤维素与纳米技术结合的产物,可主要划分为纤维素纳米纤丝、纤维素纳米晶以及细菌纤维素3类。近年来,纳米纤维素基材料作为电子器件柔性衬底、绝缘材料等研究均有许多成果问世。虽然纳米纤维素基电子器件的开发还主要停留在实验室阶段,但是与传统的石油化工产品相比,纳米纤维素具有原材料丰富、环保可降解等优点。对纳米纤维素基新型材料的开发利用,有助于解决人类社会中日益严重的电子垃圾问题。     

细菌纤维素/酚醛树脂复合透明薄膜的制备与性能

近年来石油基高分子透明薄膜的大量使用导致塑料污染问题日益严重，基于绿色环保材料制备综合性能优异的复合透明薄膜具有重要现实意义。纤维素因其绿色、环保、可再生、可持续的优点成为制备柔性复合透明材料的理想原料。本文将细菌纤维素(BC)浸渍于酚醛树脂(PF)溶液中，通过热压成型技术制备得到BC/PF复合透明薄膜，探究了酚醛树脂浓度和热压温度对BC/PF复合透明薄膜微观结构、光学性能、热稳定性、力学性能和浸润性能的影响规律。结果表明，相比于BC薄膜，BC/PF复合薄膜具有更致密的结构和更光滑的表面，透射率可达88%，力学强度、热稳定性、防水性能得到显著提高，BC/PF复合薄膜的干强度和湿强度分别是BC薄膜的2.2倍和3.4倍。本研究对于缓解塑料透明薄膜的污染和探究绿色透明薄膜的快速制备具有科学指导意义。     

纤维素导电基底及其柔性电子器件的研究进展

纤维素是自然界中含量丰富且可再生、可降解的天然材料。本文综述了物理、化学、生物或相结合的技术对纤维素的影响作用及可制备的纤维素基元材料,例如纤维素纤维、纳米纤维素和纤维素分子。基于纤维素纤维,利用湿法造纸技术可以生产具有高孔隙率的纤维素纸张基底;基于纳米纤维素,利用真空抽滤或涂布等方式可制备具有低表面粗糙度及高透明度的纳米纤维素膜基底;基于纤维素分子,利用涂布或铸涂等方式可生产具有均一的表面形态及高透明度的再生纤维素膜基底。本文进一步分析了常用的导电材料(金属导电材料、聚合物导电材料及碳基导电材料等)及其与纤维素基底结合的方法(涂布、沉积、原位聚合、自组装等),进而可以制备柔韧轻质的纤维素导电基底。基于高性能的纤维素导电基底可以组装柔性电子器件,在光电转化、能量储存及电磁屏蔽等领域展现了广阔的应用前景。总之,利用天然纤维素制备柔性电子器件对于扩大纤维素的应用范围、提升纤维素的利用价值及推动柔性电子器件的进一步发展具有重要意义。      

氧化纳米纤维素增强再生纤维素全纤维素复合薄膜的制备及性能

以2,2,6,6-四甲基哌啶-氮-氧化物(TEMPO)氧化松木粉纳米纤维素(TOCNs)为增强相、α-纤维素粉制备再生纤维素(RC)为基体,采用溶胶-凝胶法制备氧化纳米纤维素增强再生纤维素(TOCNs/RC)全纤维素复合薄膜。对不同TOCNs添加量下TOCNs/RC全纤维素复合薄膜的力学性能、光学性能、氧气阻隔性能和热稳定性能进行研究,并通过FTIR、SEM、TEM、XRD和流变仪对TOCNs和TOCNs/RC全纤维素复合薄膜的结构、形貌及纤维素溶液流变性能进行表征。结果表明,TOCNs添加量对TOCNs/RC全纤维素复合薄膜的力学性能有显著影响,当TOCNs添加量(与纤维素基体的质量比)为1.0%时,TOCNs/RC全纤维素复合薄膜的拉伸强度和断裂能分别可达134.3 MPa和21.51 MJ·m?3,具有最佳的综合力学性能;TOCNs/RC全纤维素复合薄膜的透光率随TOCNs添加量的增加而下降,雾度随TOCNs添加量的增加而增大,但仍保持较高的透光率(>85%)和较低的雾度(<14%);TOCNs/RC全纤维素复合薄膜还具有优异的氧气阻隔性,TOCNs添加量为1.6%时,其透氧系数仅为1.47×10?17cm3·cm/cm2·s·Pa。TOCNs/RC全纤维素复合薄膜有优于一般塑料薄膜的拉伸强度和氧气阻隔性,并有可媲美于塑料薄膜的透明度,可作软包装复合材料的强度层和阻隔层,在绿色高性能包装材料领域具有广阔的应用前景。      

高雾度透明纤维素薄膜制备、性能及其太阳能电池应用

将可持续的纤维素材料与电子器件结合是当今学术界的研究热点。高雾度透明纤维素薄膜是一种具有特殊光学性能的纸张。它除了具有普通纸张的优点(可降解、成本低、柔性、质轻等)外,还呈现出高的透光率和优异的光散射性能,可作为绿色光学透明材料应用于太阳能电池,提升电池的光电转化效率。本文首先简要介绍了高雾度透明纤维素薄膜的发展历程;接着,详细总结了高雾度透明纤维素薄膜的制备方法及其性能(如光学、力学、热稳定性、耐水等);然后论述了现阶段这类薄膜在太阳能电池中的应用进展;最后,总结了高雾度透明纤维素薄膜存在的科学技术问题,并对其今后的研究方向以及应用前景进行了展望。     

柔性透明导电薄膜的制备及其发展前景

随着电子器件向小型化和轻便化方向发展,柔性衬底的透明导电薄膜将成为硬质衬底透明导电薄膜的更新换代产品,因此其研究备受关注.综述了柔性透明导电膜的主要制备技术及其优缺点,阐述了当前该领域的最新研究成果及应用,并讨论了工业应用对柔性透明导电膜的性能要求及其未来发展趋势.     

还原氧化石墨烯基纳米银线透明导电薄膜研究进展

透明导电薄膜已广泛应用于印刷电子领域,传统的透明导电薄膜氧化铟锡（ITO）因其高脆性低柔韧性而不能满足高速发展的柔性电子行业;纳米银线（AgNWs）和石墨烯均具有良好光学性能、导电性能以及机械性能,使其能成为制备透明导电薄膜的理想材料。综述了近年来还原氧化石墨烯（rGO）基AgNWs透明导电薄膜的研究进展。介绍了柔性导电薄膜的关键参数及rGO/AgNWs透明导电薄膜的成膜工艺;归纳了影响rGO/AgNWs透明导电薄膜光电性能的主要因素和相关研究;阐述了rGO/AgNWs透明导电薄膜在印刷电子领域的应用现状,并展望了rGO/AgNWs透明导电薄膜的未来发展趋势。     

ITO透明导电膜制备工艺研究

电子器件柔性化、超薄化对柔性ITO透明导电膜需求越来越为迫切,但是由于ITO薄膜本身性质局限和柔性衬底问题,使得ITO透明导电膜的光电性能极容易受到影响。以PET柔性基材制备ITO膜为例,从ITO透明导电膜膜系结构出发,研究就ITO透明导电膜的制备工艺,对提高ITO透明导电膜的光电性能进行简要的探讨。     

氧化石墨烯/纳米纤维素复合薄膜的制备及表征

目的以纳米纤维素为基材,氧化石墨烯为增强相,制备氧化石墨烯/纳米纤维素复合薄膜。方法分别采用酸碱直接处理法和酸碱交替处理法制备纳米纤维素,采用一步氧化法和循环氧化膨胀法制备氧化石墨烯,观测其形貌,得出最佳制备工艺。测试由最优工艺制备的纯纤维素薄膜和复合薄膜的拉伸和润湿性能。结果酸碱交替处理法制备的纳米纤维素薄膜表面结构清晰,且纤维直径可达50 nm,循环氧化-膨胀法制备的氧化石墨烯片层厚度在纳米级别。当纳米纤维素与氧化石墨烯的质量比为20∶1时,氧化石墨烯/纳米纤维素复合薄膜的拉伸强度达149.68MPa,与纯纤维素薄膜相比增加了19.55%,且复合薄膜的接触角大于纯纤维素薄膜的。结论证实了氧化石墨烯能够增强纳米纤维素薄膜,在一定程度上说明氧化石墨烯/纤维素复合薄膜对水分子的阻隔性优于纤维素薄膜。     

纳米纸衬底的制备、性能及其在柔性电子器件中的应用

由纳米纤维素制备的纳米纸具有天然可降解、质量轻、柔性好、透明度高、强度高、热稳定性好以及可卷对卷生产等优良特性,被视为柔性电子器件衬底的理想材料之一。近年来,人类社会对电子垃圾引起的环境问题逐渐重视,使得绿色纳米纸衬底成为学术界和工业界的研究热点之一。本文综述了用于柔性电子器件的纳米纸衬底的最新研究进展,详细探讨了纳米纸衬底的制备、性能及其在器件应用方面的研究成果,着重阐述了纳米纸衬底在有机薄膜晶体管、太阳能电池以及有机发光二极管中的应用现状。最后,进一步总结了现阶段纳米纸衬底在器件应用过程中存在的问题,如纳米纸制备效率低、对纳米纸进行性能调控和优化以满足电子器件的要求等,并对未来应用前景进行了展望。     

Anisotropic,Transparent Films with Aligned Cellulose Nanofibers

Transparent films or substrates are ubiquitously used in photonics and optoelectronics, with glass and plastics as traditional choice of materials. Transparent films made of cellulose nanofibers are reported recently. However, all these films are isotropic in nature. This work, for the first time, reports a remarkably facile and effective approach to fabricating anisotropic transparent films directly from wood. The resulting films exhibit an array of exceptional optical and mechanical properties. The well‐aligned cellulose nanofibers in natural wood are maintained during delignification, leading to an anisotropic film with high transparency (≈90% transmittance) and huge intensity ratio of transmitted light up to 350%. The anisotropic film with well‐aligned cellulose nanofibers has a mechanical tensile strength of up to 350 MPa, nearly three times of that of a film with randomly distributed cellulose nanofibers. Atomistic mechanics modeling further reveals the dependence of the film mechanical properties on the alignment of cellulose nanofibers through the film thickness direction. This study also demonstrates guided liquid transport in a mesoporous, anisotropic wood film and its possible application in enabling new nanoelectronic devices. These unique and highly desirable properties of the anisotropic transparent film can potentially open up a range of green electronics and nanofluidics.     

High Dielectric Performances of Flexible and Transparent Cellulose Hybrid Films Controlled by Multidimensional Metal Nanostructures

Various wearable electronic devices have been developed for extensive outdoor activities. The key metrics for these wearable devices are high touch sensitivity and good mechanical and thermal stability of the flexible touchscreen panels (TSPs). Their dielectric constants (k) are important for high touch sensitivities. Thus, studies on flexible and transparent cover layers that have high k with outstanding mechanical and thermal reliabilities are essential. Herein, an unconventional approach for forming flexible and transparent cellulose nanofiber (CNF) films is reported. These films are used to embed ultralong metal nanofibers that serve as nanofillers to increase k significantly (above 9.2 with high transmittance of 90%). Also, by controlling the dimensions and aspect ratios of these fillers, the effects of their nanostructures and contents on the optical and dielectric properties of the films have been studied. The length of the nanofibers can be controlled using a stretching method to break the highly aligned, ultralong nanofibers. These nanofiber‐embedded, high‐k films are mechanically and thermally stable, and they have better Young's modulus and tensile strength with lower thermal expansion than commercial transparent plastics. The demonstration of highly sensitive TSPs using high‐k CNF film for smartphones suggests that this film has significant potential for next‐generation, portable electronic devices.     

A Transparent,Skin-Inspired Composite Film with Outstanding Tear Resistance Based on Flat Silk Cocoon

Flexible and transparent substrates play a fundamental role as a mechanical support in advanced electronic devices. However, commonly used polymer films, such as polydimethylsiloxane, show low tear resistance because of their crack sensitivity. Herein, inspired by the excellent mechanical robustness of the skin and its fibrous structure, an epoxy-resin-based composite with a flat silk cocoon as a reinforcing fiber network is fabricated. With only 1 wt% of silk fiber, the tensile strength and modulus of the as-prepared composite film are considerably increased by 300% and 612% compared to those of pure resin, while still maintaining flexibility and transparency. More importantly, the composite shows remarkable tear resistance: without fracture after ≈30 000 tensile cycles. The potential application of such transparent composite films as mechanically robust substrates for flexible electronics is also demonstrated. In addition, this study represents a bioinspired strategy to construct high-performance functional composite materials.     

Printed transparent electrodes containing carbon nanotubes for elastic circuits applications with enhanced electrical durability under severe conditions

Organic composites filled with nanostructures are new group of materials with unique physical properties. Carbon nanotubes (CNTs) are demonstrating good electrical and mechanical properties. This enables to produce conductive polymer-CNT thick films optically transparent, which are highly useful in production of printed electronic paper. Currently used indium tin oxide (ITO) and antimony tin oxide (ATO) films exhibit high optical transmittance with reasonable electrical conductivity, but very low resilience to mechanical stresses. This is one of the key problems in fabrication of flexible electronic displays. Current authors’ achievements include fabrication of transparent electrodes obtained by screen printing technique, used for production of fully functional thick film electroluminescent structures.     

磁性纳米纤维素复合膜的制备

目的用简易、经济的方法制备透明柔性、可折叠、力学性能良好的茶梗纳米纤维素基磁性复合膜。方法以茶梗纳米纤维素晶体(CNCs)为模板,共沉淀合成磁性CNCs;随后将磁性CNCs分散到茶梗纳米纤维素纤丝(NCFs)溶液中;最后通过真空抽滤的方法制备磁性复合膜。结果磁性CNCs在不需要任何分散剂的情况下,可以均匀地分散在水溶液中,具有良好的超顺磁性;磁性复合膜具有良好的光学、力学和磁学性能,当NCFs质量分数为60%时,透光率、拉伸强度和磁化强度分别达到71.3%,75.03 MPa和12.96 A·m~2/kg。结论制备的磁性CNCs具有良好的分散性和磁学性能;磁性复合膜具有较好磁学和力学性能,可考虑在电磁屏蔽、磁电开关等领域进行应用。     

Influence of the cellulose substrate on the electrochemical properties of paper-based polypyrrole electrode materials

The influence of the cellulose substrate on the electrochemical performance of supercapacitor electrode materials made of polypyrrole (PPy) and cellulose is investigated. Composites were synthesized by chemical polymerization of pyrrole on dispersed fibers of cellulose from Cladophora algae and dispersed wood cellulose-based commercial filter papers, respectively, as well as on Cladophora cellulose and filter paper sheets. The resulting composites, which were characterized using scanning electron microscopy, cyclic voltammetry, and elemental analysis, were found to exhibit specific charge capacities proportional to the PPy content of the composites. The highest specific capacity (i.e., 171 C/g composite or 274 C/g PPy) was obtained for composites made from dispersed Cladophora cellulose fibers. The higher specific capacities for the Cladophora cellulose composites can be explained by the fact that the Cladophora cellulose fibers were significantly thinner than the wood cellulose fibers. While the PPy was mainly situated on the surface of the Cladophora cellulose fibers, a significant part of the PPy was found to be present within the wood fibers of the filter paper-based composites. The latter can be ascribed to a higher accessibility of the aqueous pyrrole solution to the wood-based fibers as compared to the highly crystalline algae based cellulose fibers. The present results clearly show that the choice of the cellulose substrate is important when designing electrode materials for inexpensive, flexible and environmentally friendly paper-based energy storage devices.     

羧甲基纤维素增强膜的制备及性能

目的为了获得一种可用于食品包装的羧甲基纤维素增强膜。方法以羧甲基纤维素(CMC)为成膜基底,甘油为增塑剂,分别将质量分数为1%,3%,5%和10%的纳米纤维素(NCC)添加到CMC中,共混流延制备羧甲基纤维素增强膜(CMC-NCC)。结果 NCC的加入,提高了CMC的力学性能和对水蒸气的阻隔性能,还提高了CMC的热性能。FT-IR分析结果表明,CMC与NCC两者间形成了分子间氢键;XRD分析结果表明,NCC可以改变CMC的结晶排列。当添加质量分数为5%的NCC时,CMC-NCC的拉伸强度比纯CMC膜提高了25.6%,断裂伸长率降低了21.3%,透湿量降低了9%,热稳定性提高了2%,透光率维持在87%以上。结论 CMC增强膜具有力学性能高、阻湿性能好等优点,NCC提高了CMC的成膜品质。     

Micromechanics of TEMPO-oxidized fibrillated cellulose composites

Composites of poly(lactic) acid (PLA) reinforced with TEMPO-oxidized fibrillated cellulose (TOFC) were prepared to 15, 20, 25, and 30% fiber weight fractions. To aid dispersion and to improve stress transfer, we acetylated the TOFC prior to the fabrication of TOFC-PLA composite films. Raman spectroscopy was employed to study the deformation micromechanics in these systems. Microtensile specimens were prepared from the films and deformed in tension with Raman spectra being collected simultaneously during deformation. A shift in a Raman peak initially located at ~1095 cm(-1), assigned to C-O-C stretching of the cellulose backbone, was observed upon deformation, indicating stress transfer from the matrix to the TOFC reinforcement. The highest band shift rate, with respect to strain, was observed in composites having a 30% weight fraction of TOFC. These composites also displayed a significantly higher strain to failure compared to pure acetylated TOFC film, and to the composites having lower weight fractions of TOFC. The stress-transfer processes that occur in microfibrillated cellulose composites are discussed with reference to the micromechanical data presented. It is shown that these TOFC-based composite materials are progressively dominated by the mechanics of the networks, and a shear-lag type stress transfer between fibers.