Electrochromic performance of PECVD-synthesized WOxCy thin films on flexible PET/ITO substrates for flexible electrochromic devices

Electrochromic performance of WO_xC_y films deposited onto 60 Ω/□ flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates by low temperature plasma-enhanced chemical vapor deposition (PECVD) was investigated. It was proven that extraordinary electrochromic performance was provided when the precursor [tungsten carbonyl, W(CO)₆; TC] vapor, carried by argon gas, was mixed with air gas and synthesized by radio frequency (r.f.) power at room temperature (23 °C). Cyclic voltammetry switching measurements found that only low driving voltages from − 1 V to 1 V were needed to provide reversible Li⁺ ion intercalation and de-intercalation. The light modulation with up to 63.6% of transmittance variation at a wavelength of 650 nm was obtained for 150 cycles of Li⁺ intercalation and de-intercalation in a 0.1 M LiClO₄-PC (propylene carbonate) electrolyte.     

Self-healing flexible/stretchable energy storage devices

During the past decade, flexible/stretchable energy storage devices have garnered increasing attention, with the successful development of wearable electronics. However, due to the repeated deformation accompanied with the electrochemical depletion process, these devices suffer from unavoidable damage, including cracks, crazing, puncture and delamination, which can lead to serious performance degradation or even safety issues. Simultaneously, inspired by biological organs, self-healing capability is found to be a promising approach to address these issues by restoring the mechanical and electrochemical performance. This review first summarizes the structural design and features of various flexible/stretchable energy storage devices, from 1D to 3D configurations. Then, basic concepts and three self-healing mechanisms, including capsule-based systems, vascular-based systems, and intrinsic healing systems are analyzed along with a brief look at existing applications. Then we review all the important parts of state-of-art flexible/stretchable self-healing supercapacitors and batteries including electrodes, electrolytes, substrates and encapsulation. Moreover, a detailed evaluation of methodologies for flexibility, stretchability and self-healing capabilities are described in detail. Finally, the critical challenges and prospects of future promising solutions for self-healing flexible/stretchable energy storage devices or even electronics are provided.     

TCO/metal/TCO structures for energy and flexible electronics

There is increasing attention paid to improving transparent conductive electrodes for applications in large area photovoltaic devices and displays that are being developed for energy and electronics. To date, transparent and conductive oxides (TCO) based on In₂O₃, ZnO, or SnO₂ are commonly used, but advanced devices require new electrodes with lower resistivities than previously achieved and with optical properties superior to those of the present generation. TCO/metal/TCO multilayer structures have emerged as an interesting alternative because they provide optical and electrical characteristics globally superior to those attainable with a single-layer TCO or metal electrode and can be deposited at low temperatures onto inexpensive plastic substrates. Indeed, the fabrication of thin film devices on flexible substrates has substantial interest for application to lightweight products and implementation of roll-to-roll deposition processes that can significantly reduce production costs. In this sense, organic electronics that require low deposition temperatures have the best chance to be the first transferred from conventional glass to inexpensive plastic substrates. The present critical review summarizes current TCO/metal/TCO research results, first analyzed for materials and thickness selection as a function of the optical transmittance and electrical resistance parameters, and then analyzed according to other important properties such as mechanical reliability and thermal and humidity stability. The review concludes with a brief discussion of the results obtained for TCO/metal/TCO structures applied as electrodes in several organic electronic devices.     

Electrochromic performance of NiVxOy thin films deposited onto flexible PET/ITO substrates by reactive plasma sputtering for flexible electrochromic devices

An investigation was conducted on the electrochromic properties of plasma sputtered-nickel-vanadium oxide thin films on 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates. Metallic Ni_0.93V_0.07 target, sputtered by radio frequency power with argon gases and reacted with oxygen gases at room temperature (23 °C), was proven to provide extraordinary electrochromic performance. Cyclic voltammetry switching measurements found that only low driving voltages from − 1 V to 1 V were needed to provide reversible Li⁺ ion intercalation and deintercalation. The light modulation with up to 52% of transmittance variation, optical density change of 0.446 and color efficiency of 63.8 cm²/C at a wavelength of 550 nm was obtained for 200 cycles of Li⁺ intercalation and deintercalation in a 1 M LiClO₄-propylene carbonate electrolyte.     

Graphene-based flexible NO2 chemical sensors

We demonstrated graphene-based flexible NO₂ chemical sensors on polyethylene terephthalate substrate where graphene was grown on Cu-foil by chemical vapor deposition technique. Introduction of NO₂ molecules to graphene caused a rapid increase in the currents due to the charge transfer between NO₂ molecules and graphene under both relaxed and strained conditions. However, the recovery was delayed due to slow desorption of NO₂ molecules from defective sites in graphene. Also, strain in graphene increased the resistance of graphene layer where the change in conductance was reversible. Our graphene-based NO₂ chemical sensors showed a great sensitivity and reproducibility under both strained and relaxed conditions.     

Bio-inspired micro/nanostructures for flexible and stretchable electronics

The remarkable ability of biological systems to sense and adapt to complex environmental conditions has inspired the design of next-generation electronics with advanced functionalities. This review focuses on emerging bio-inspired strategies for the development of flexible and stretchable electronics that can accommodate mechanical deformations and integrate seamlessly with biological systems. We will provide an overview of the practical considerations in the materials and structure designs of flexible and stretchable electronics. Recent progress in bio-inspired pressure/strain sensors, stretchable electrodes, mesh electronics, and flexible energy devices are then discussed, with an emphasis on their unconventional micro/nanostructure designs and advanced functionalities. Finally, current challenges and future perspectives are identified and discussed.

     

钡铁氧体/石墨烯/二氧化硅柔性复合材料吸波性能的研究

随着信息化时代的快速发展,各种各样的电子产品也被广泛地应用到生活与工作中,伴随其而来的电磁污染也成为日益严重的问题,具有“薄、轻、宽、强”的吸波材料得到了广泛的关注。采用机械混合法将钡铁氧体(BaFe₁₂O₁₉)、石墨烯（graphene）、二氧化硅（SiO₂）进行混合,制备多元复合吸波剂,以水性聚氨酯为粘结剂,使用流延工艺制备多元复合吸收剂涂层织物,并分析其结构、形貌、机械以及吸波性能。结果表明,所制备的柔性吸波涂层织物在吸波剂配比为0.4(BaFe₁₂O₁₉-graphene)-0.6SiO₂、吸波涂层厚度为1.2 mm时,最小反射损耗达到-14.58 dB,有效吸波带宽为0.94 GHz（12.91～13.58 GHz）,具备涂层薄、吸波强度高、吸收频带宽、质量轻的潜质。     

碳纤维/棉纤维/聚吡咯柔性复合材料的制备及性能研究

柔性超级电容器作为一种储能器件,具有功率密度高、充电时间短、循环寿命长、比电容高等优点,可满足可穿戴器件的需求,而柔性电极材料是决定柔性超级电容器发展的关键因素,它决定着电容器的主要性能指标。采用混纺的方法制备了碳纤维含量为20%(质量分数)的碳纤维/棉纤维混纺纱线,然后通过电化学沉积法在碳纤维/棉纤维混纺纱线上生长聚吡咯颗粒,成功制备了20%(质量分数)碳纤维/棉纤维/聚吡咯柔性复合材料。利用扫描电子显微镜、拉曼光谱分析仪和电化学工作站研究了复合材料的形貌、聚吡咯沉积情况以及复合材料的电容性能。结果表明,20%(质量分数)碳纤维/棉纤维/聚吡咯柔性复合材料中,聚吡咯颗粒直径为30~60 nm,且沉积均匀,化学活性较高;在1.02 mA/cm^2电流密度下,复合材料的最大比电容达到1.28 F/cm^2,其高比电容归因于电极的独特结构;复合材料具有良好的柔韧性、机械稳定性和充放电循环寿命,其经过6000次弯曲循环后,电容保持率仍有80%以上,可以用作柔性可穿戴超级电容器的电极材料。     

Transparent and flexible cellulose nanofibers/silver nanowires/acrylic resin composite electrode

In this study, we report a novel, eco-friendly and simple method to fabricate cellulose nanofibers (CNFs)/silver nanowires (AgNWs)/acrylic resin (AR) composite electrode. CNFs with average diameter of 15 nm were disintegrated only by one time-pass grinding. Aqueous dispersion of AgNWs was embedded onto the surface of CNFs film by simple vacuum filtration. The final composite electrode was obtained by impregnating CNFs/AgNWs film to AR with the assist of adhesive tape. This electrode with AgNWs density of 134 mg/m² showed low sheet resistance (4 Ω/sq), and high light transmittance (85%) which was 6% lower than that of neat AR. The coefficient of thermal expansion of the composite electrode was as low as 25.32 ppm K⁻¹. The tensile strength and Young’s modulus of CNFs/AgNWs/AR composite film were 35.71 MPa and 1.63 GPa, which were about 8 and 5.8 times larger than neat AR film, respectively.     

Photo-rewritable flexible LCD using indium zinc oxide/polycarbonate substrates

This work presents a photo-rewritable transmissive flexible-LCD based on the alignment effect of the photo-induced adsorption of azo dye on flexible indium zinc oxide/polycarbonate (IZO/PC) substrates. Images can be displayed without applying an external field and rewritten by changing the direction of the writing laser beam while the cell temperature is controlled. By using IZO/PC substrates, the writing and erasing processes can be achieved within 1 min with a high contrast.     

Modified holographic recording setup for photopolymerizable/flexible recording materials

An improvement in the conventional holographic recording setup has been done for liquid (photopolymerizable) or flexible recording materials. The new vertical recording setup that comprises a horizontal substrate holder permits holographic recording on such materials without positioning them between two substrates, as has been done until now. This setup can be conveniently used for the fabrication of transmission, reflection, Fourier transform, and computer-generated holograms with few simple modifications as indicated.     

High-strain sensors based on ZnO nanowire/polystyrene hybridized flexible films

A type of strain sensor with high tolerable strain based on a ZnO nanowires/polystyrene nanofibers hybrid structure on a polydimethylsiloxane film is reported. The novel strain sensor can measure and withstand high strain and demonstrates good performance on rapid human-motion measurements. In addition, the device could be driven by solar cells. The results indicate that the device has potential applications as an outdoor sensor system.     

Novel flexible photoanode based on Ag nanowire/polymer composite electrode

A novel flexible photoanode based on a silver nanowire (AgNW)/polymer composite electrode was fabricated and used for dye-sensitized solar cells. The AgNW/polymer composite substrate comprised a thin percolation network of AgNWs embedded on the surface of polyacrylic ester. As titanium dioxide film formed on top of the composite substrate, the effect of compression was investigated. Drop-cast sensitization was then used for both pressed and nonpressed photoanode, and the nonpressed one performed better. A cell efficiency of 0.91% was achieved under 100 mW cm^?2 simulated solar irradiation. After a bending test on the flexible photoanode, the solar cell retained 0.71% efficiency.     

钙钛矿太阳能电池用Ag/ZrO2/C柔性纳米纤维膜电极

钙钛矿太阳能电池(perovskite solar cells,PSCs)因其制备简单、光电转化效率较高等优点而备受关注.静电纺碳纳米纤维膜(carbon nanofiber films,CNFs)具有高比表面积、良好的电学性能和化学稳定性,但其脆性限制了它的应用.利用静电纺丝法结合水热法制备柔性导电Ag/ZrO2/C复合纳米纤维膜,然后将其应用于PSCs的对电极,研究不同Ag纳米颗粒添加量对柔性复合纳米纤维膜和电池的性能影响.结果表明:当银前驱体溶液质量浓度从0 g/mL增加至0.030 g/mL时,Ag/ZrO2/C复合纳米纤维表面的Ag纳米颗粒的包覆越来越好,薄膜显示良好的柔韧性,其抗弯弹性模量为0.479 MPa,电导率从866 S/m增加到4862 S/m,提高了薄膜的空穴电子传输能力,进而增强PSCs的性能.当溶液质量浓度为0.030 g/mL时,器件具备最优的光电转换效率(6.05％)和最大电流(18.44 mA/cm2).     

Reliable high temperature,high humidity flexible thin film encapsulation using Al2O3/MgO nanolaminates for flexible OLEDs

Since most organic materials are very sensitive to moisture and oxygen, organic light emitting diodes (OLEDs) require an encapsulation layer to protect the active layer from these gases. Since light, flexible and portable OLEDs are being employed in more diverse climates and environmental conditions, the OLED encapsulation layer must retain robust mechanical properties and stability in high temperature/high humidity conditions. Al₂O₃ films have demonstrated excellent barrier performance, but they readily hydrolyze when exposed to prolonged harsh environments. In this study, we fabricated a thin film encapsulation (TFE) film that was resistant to hydrolysis, using Al₂O₃/MgO (AM) nanolaminates. MgO has superior resistance to harsh environments, and the aluminate phase generated by the chemical reaction of Al₂O₃ and MgO provided excellent barrier performance, even after storage in harsh conditions. A multi-barrier fabricated using the AM nanolaminate showed excellent barrier performance, close to the level required by OLEDs. It did not significantly deteriorate even after a bending test of 1,000 iterations at 0.63% strain. After 1,000 cycle of bending, the electrical properties of the passivated OLEDs were not significantly degraded at shelf-lifetime test where the fabricated device was stored for 50 days in a harsh environment of 60 °C, 90% relative humidity. The multi-barrier shows the best performance compared to previous studies on flexible encapsulation that can be used in harsh environments.

     

纳米纤维素-聚吡咯/天然橡胶柔性导电弹性体的制备与性能

以纤维素纳米纤丝（Cellulose nanofibrils,CNFs）为生物模板,将聚吡咯（Polypyrrole,PPy）原位聚合在CNFs表面,再将CNF-PPy复合物均匀分散到天然橡胶（Natural rubber,NR）弹性基体中,制备了具有高柔韧性的纳米纤维素-聚吡咯/天然橡胶（CNF-PPy/NR）导电弹性体。结果表明：CNFs可协助PPy在NR基体中形成三维导电网络结构,并提高弹性体的力学性能和导电性能,有效降低其逾渗阈值。当添加质量比为5%（以橡胶质量为基准,下同）的CNF和20%的PPy时,CNF-PPy/NR的拉伸强度可达（8.97±0.92）MPa,分别约为PPy/NR及纯NR的1.56倍和9.54倍,电导率可达（0.134±0.063）S/m;在0.3 A/g的电流密度下,比电容可达96 F/g,并在1.0 A/g电流密度下循环充放电1 200次后,比电容仍可保持其初始值的72%。此导电弹性体具有良好的力学强度和电学性能,有望应用于柔性有机电子器件领域。     

Silver flake/polyaniline composite ink for electrohydrodynamic printing of flexible heaters

Journal of Materials Science: Materials in Electronics - Printed flexible electrical heaters with excellent heating performance and mechanical durability are highly desirable for deicing and...     

Performance evaluation of a flexible machining/assembly system and routing comparisons

This paper discusses the performance evaluation of the flexible machining/assembly systems (FMS/FAS) of a central server type, and gives a comparative consideration of a fixed, dynamic versus an ordered-entry routing rule. First, the steady-state equations are given, and the system throughput is obtained. Next, the system configurations of FMS/FAS are numerically discussed on the basis of system throughput. Finally, the superiority of an ordered-entry routing rule is numerically discussed for development of routing theory.     

Conductive polypyrrole incorporated nanocellulose/MoS2 film for preparing flexible supercapacitor electrodes

Conductive films have emerged as appealing electrode materials in flexible supercapacitors owing to their conductivity and mechanical flexibility. However, the unsatisfactory electrode structure induced poor output performance and undesirable cycling stability limited their application. Herein, a well-designed film was manufactured by the vacuum filtration and in-situ polymerization method from cellulose nanofibrils (CNFs), molybdenum disulfide (MoS₂), and polypyrrole. The electrode presented an outstanding mechanical strength (21.3 MPa) and electrical conductivity (9.70 S·cm⁻¹). Meanwhile, the introduce of hydrophilic CNFs induced a desirable increase in diffusion path of electrons and ions, along with the synergistic effect among the three components, further endowed the electrode with excellent specific capacitance (0.734 F·cm⁻²) and good cycling stability (84.50% after 2000 charge/discharge cycles). More importantly, the flexible all-solid-state symmetric supercapacitor delivered a high specific capacitance (1.39 F·cm⁻² at 1 mA·cm⁻²) and a volumetric energy density (6.36 mW·h·cm⁻³ at the power density of 16.35 mW·cm⁻³). This work provided a method for preparing composite films with desired mechanical and electrochemical performance, which can broaden the high-value applications of nanocellulose.