Room Temperature Electrochemical Sintering of Zn Microparticles and Its Use in Printable Conducting Inks for Bioresorbable Electronics

This study describes a conductive ink formulation that exploits electrochemical sintering of Zn microparticles in aqueous solutions at room temperature. This material system has relevance to emerging classes of biologically and environmentally degradable electronic devices. The sintering process involves dissolution of a surface passivation layer of zinc oxide in CH₃COOH/H₂O and subsequent self‐exchange of Zn and Zn²⁺ at the Zn/H₂O interface. The chemical specificity associated with the Zn metal and the CH₃COOH/H₂O solution is critically important, as revealed by studies of other material combinations. The resulting electrochemistry establishes the basis for a remarkably simple procedure for printing highly conductive (3 × 10⁵ S m^?1) features in degradable materials at ambient conditions over large areas, with key advantages over strategies based on liquid phase (fusion) sintering that requires both oxide‐free metal surfaces and high temperature conditions. Demonstrations include printed magnetic loop antennas for near‐field communication devices.     

等离子体诱导铜油墨低温固化工艺及性能优化

目的 利用低温等离子体诱导铜络合物导电油墨实现在柔性基板上快速固化,制备出高导电柔性铜薄膜,并阐明油墨溶剂质量分数、预热处理时间、等离子体功率、处理时间等参数对铜膜固化结构与导电特性的影响规律。方法 通过调节油墨中的溶剂质量分数以改变油墨的铜含量及印刷铜薄膜的厚度;通过控制变量法优化低温固化工艺,并利用扫描电子显微镜、共聚焦显微镜、电阻率测量等手段表征柔性薄膜的物理特性;通过圆珠笔直写和卷对卷印刷方式测试所制备油墨与工艺在印刷柔性电子领域的适用性。结果 通过对油墨配方和等离子体处理工艺的协同优化,可以制备最薄为40 nm,最低电阻率为3.76 μΩ?cm的柔性铜薄膜。结论 等离子体处理可以实现铜络合物油墨的低温快速固化制备高性能铜薄膜,在印刷柔性电子领域展现出了巨大的应用潜力。     

Printable Transparent Conductive Films for Flexible Electronics

Printed electronics are an important enabling technology for the development of low‐cost, large‐area, and flexible optoelectronic devices. Transparent conductive films (TCFs) made from solution‐processable transparent conductive materials, such as metal nanoparticles/nanowires, carbon nanotubes, graphene, and conductive polymers, can simultaneously exhibit high mechanical flexibility, low cost, and better photoelectric properties compared to the commonly used sputtered indium‐tin‐oxide‐based TCFs, and are thus receiving great attention. This Review summarizes recent advances of large‐area flexible TCFs enabled by several roll‐to‐roll‐compatible printed techniques including inkjet printing, screen printing, offset printing, and gravure printing using the emerging transparent conductive materials. The preparation of TCFs including ink formulation, substrate treatment, patterning, and postprocessing, and their potential applications in solar cells, organic light‐emitting diodes, and touch panels are discussed in detail. The rational combination of a variety of printed techniques with emerging transparent conductive materials is believed to extend the opportunities for the development of printed electronics within the realm of flexible electronics and beyond.     

金属纳米颗粒导电墨水制备与后处理工艺的研究进展

印刷电子技术是一种低成本、简捷高效、绿色环保的电子器件制造技术,已在柔性电子制造等诸多领域展现出巨大的潜力。近年来,导电墨水作为印刷电子技术迅速发展的关键材料受到了学术界的广泛关注和报道。结合印刷电子技术的应用和发展现状,对金属纳米颗粒导电墨水的各项性能指标及其机理进行概述,综述了金属纳米颗粒导电墨水的制备和后处理工艺的研究进展,着重介绍了部分有潜力的前沿技术,并分析了这些技术对应的优势与局限及其发展方向。最后结合印刷电子技术目前发展中存在的问题提出了一些观点。     

Reversible Conductive Inkjet Printing of Healable and Recyclable Electrodes on Cardboard and Paper

Conductive inkjet printing with metal nanoparticles is irreversible because the particles are sintered into a continuous metal film. The resulting structures are difficult to remove or repair and prone to cracking. Here, a hybrid ink is used to obviate the sintering step and print interconnected particle networks that become highly conductive immediately after drying. It is shown that reversible conductive printing is possible on low‐cost cardboard samples after applying standard paper industry coats that are adapted in terms of surface energy and porosity. The conductivity of the printed films approaches that of sintered standard inks on the same substrate, but the mobility of the hybrid particle film makes them less sensitive to cracks during bending and folding of the substrate. Damages that occur can be partially repaired by wetting the film such that particle mobility is increased and particles move to bridge insulating gaps in the film. It is demonstrated that the conductive material can be recovered from the cardboard at the end of its life time and be redispersed to recycle the particles and reuse them in conductive inks.     

无颗粒型银导电墨水的制备及其性能研究

首先以硝酸银作为银源,制备出柠檬酸银和碳酸银,然后以柠檬酸银和碳酸银为金属前驱体化合物,异丙胺为络合剂,甲醇为还原剂,另加入少量添加剂以调节粘度和表面张力等物理参数,制得无颗粒银导电墨水。该银导电墨水可以采用A4平板打印机在PET(Polyethylene terephthalate)上打印图案,并在较低的热处理温度下即可获得导电性较好的银膜。利用X射线衍射仪、扫描电子显微镜、四探针测试仪、接触角测量仪、傅里叶变换红外光谱仪、热分析仪对柠檬酸银、碳酸银、导电墨水及导电银膜进行测试表征。结果表明导电墨水经130℃热处理之后,导电银膜由均匀的纳米银颗粒组成;经130℃热处理40min后,得到的银膜的方块电阻可低至0.84Ω·□~(-1),可广泛用于电子印刷行业。     

Inkjet-Printed Metal Oxide/PEDOT:PSS-Based Diodes and Rectifiers for Wireless Power Transfer

Printed electronic circuits are beginning to attract commercial success in different areas of applications that include low-cost wearables, biosensors, biomedical tags, packaging, e-textiles, etc. However, the major part of the research in this domain has always been focused on developing high-performance thin-film transistors (TFTs), while the other essential circuit elements, that are required, for example, for low-loss conversion of the input power, have rarely been reported. In this regard, inkjet-printed amorphous oxide-based diodes on glass, and flexible polyimide substrates with rectification ratio >10⁴ and operation frequency up to 25 and 15 MHz, respectively, are demonstrated. Next, using the printed diodes’ full-wave and double half-wave rectifiers are fabricated to convert input AC signals to DC supply. In addition, wireless power transfer (WPT) is demonstrated, where the input AC signal is wirelessly transmitted from a distance of 3 cm, at 125 kHz. The demonstrated WPT technology can be suitable for invasive implantable devices and standalone systems in multiple mediums. Finally, bending fatigue tests are carried out with the printed diodes on flexible substrates, down to a bending radius of 2.5 mm to demonstrate tensile strain tolerance up to 2.5%.     

纳米银导电油墨及其在柔性印刷电子中的应用

目的 探究纳米银导电油墨及其在柔性印刷电子中的应用。方法 通过总结国内外文献,从纳米银颗粒及其导电油墨的制备、印刷工艺、烧结工艺以及在柔性印刷电子技术中的应用几方面总结近年来的研究进展。结果 在油墨制备及使用中,简化制备工艺、降低生产成本、实现绿色环保、低温烧结,同时提高油墨的基材适应性是未来纳米银导电油墨的改进重点。直写技术具有精度高、速度快等优势,正逐渐替代丝网印刷技术成为主流。烧结工艺的研究重点在于实现低温烧结,其中化学烧结工艺简单,但提高导电性是研究重点。其他烧结方式则设备昂贵,环境要求高。结论 作为功能性电子材料,纳米银导电油墨因出色的电性能和印刷适性,正在被广泛应用于柔性印刷电子中。近年来通过对纳米银及其导电油墨的深入研究及技术改进,在纳米银颗粒的制备、低温烧结技术、节能环保加工工艺等方面获得了一定的进展。与此同时,将其作为功能材料应用于制备柔性传感器中,RFID标签天线、柔性电极、超级电容器、太阳能电池等正受到广泛研究与应用。     

Control of the Surface Morphology of Ceramic/Polymer Composite Inks for Inkjet Printing

The use of organic/inorganic composite inks in the Drop on Demand inkjet printing technology is a promising as well as demanding approach for the fabrication of composite thick films. Therefore, a versatile ceramic/polymer composite ink system for inkjet printing is developed in this study, containing Ba_0.6Sr_0.4TiO₃ (BST) and poly(methyl methacrylate) (PMMA). When developing such inks suitable for a one‐step fabrication, the major challenge is to fulfill the requirements of the inkjet printing technology and to obtain homogeneous surface morphologies after drying. Thus, possible influencing factors like the solvent composition, the solids content, and the ratio of ceramic to polymer are investigated to obtain a detailed knowledge for the general ink development. The fluid mechanical properties, viscosity, density, and surface tension are characterized. The main focus of this study lies on the drying behavior of the different inks, with the interactions of the ceramic particles, and the dissolved polymer molecules being highlighted. Furthermore, the drying behavior depending on the ink composition is shown. This study provides new insights into the possibility of using composite inks for the inkjet printing process and the fabrication of printed composite thick films in a single process step.

     

Rapid Low‐Temperature 3D Integration of Silicon Nanowires on Flexible Substrates

The vertical integration of 1D nanostructures onto the 2D substrates has the potential to offer significant performance gains to flexible electronic devices due to high integration density, large surface area, and improved light absorption and trapping. A simple, rapid, and low temperature transfer bonding method has been developed for this purpose. Ultrasonic vibration is used to achieve a low temperature bonding within a few seconds, resulting in a polymer‐matrix‐free, electrically conducting vertical assembly of silicon nanowires (SiNWs) with a graphene/PET substrate. The microscopic structure, and mechanical and electrical characteristics of the interface between the transferred SiNW array and graphene layer are subsequently investigated, revealing that this creates a mechanically robust and electrically Ohmic contact. This newly developed ultrasonic transfer bonding technique is also found to be readily adaptable for diverse substrates of both metal and polymer. It is therefore considered as a valuable technique for integrating 1D vertical nanostructures onto the 2D flexible substrates for flexible photovoltaics, energy storage, and water splitting systems.     

凹胶印刷电子油墨铺展过程分析及实验

目的 为清晰直观地认识凹胶印刷电子油墨铺展过程的微观机理。方法 根据油墨铺展运动过程,建立其静态的物理和几何模型,利用幂律流体理论,分析油墨粘度与剪切速率之间的关系,特别是纳米银导电油墨的幂律流体函数模型,最后利用实验验证这一模型的正确性。结果 幂律流体理论表明,纳米银导电油墨的粘度与剪切速率存在 的数量关系,实验结果表明,在印刷压力为49 N,线宽扩大率最大时,印刷速度为21.88 mm/s,验证该条件下的方阻值为5.915 Ω;在印刷速度为45 mm/s,线宽扩大率最大时,印刷压力为49.36 N,验证该条件下的方阻值为5.908 Ω;在印刷压力为49 N,印刷速度为45 mm/s下,线宽扩大率最大时,油墨粘度为0.78 Pa?s,验证该条件下的方阻值为4.8998 Ω;油墨粘度η与印刷速度v之间存在 的函数关系。结论 纳米银导电油墨是一种假塑性流体,其粘度与剪切速率呈负相关变化,剪切速率是影响油墨铺展过程的关键参数。