柔性电子喷印制造中非牛顿流体液滴生成和冲击动力学研究

柔性电子的最新进展为折叠显示、精准医疗等领域注入了新的活力。喷印技术无需模板，可直接在大面积、可变形基底上制备电子器件，是柔性电子理想的制造方式。喷印过程使用的墨液是黏度高、包含各向异性一维/二维功能材料的非牛顿流体，但目前对微米尺度非牛顿流体液滴的可控生成及冲击动力学研究匮乏，制约了喷印精度和效率的发展。本项目针对新型功能墨液的流变特性和微米液滴冲击的极高剪切率特征，研究百纳秒时域、微米尺度、十兆赫兹剪切率参数空间下的液滴冲击动力学，旨在发现非牛顿流体微纳液滴冲击过程的新现象，探索高剪切率引发的流变行为及其对液滴铺展变形影响的新规律，建立强剪切流对各向异性功能材料单元排列和聚集诱导的新模型，揭示关键流体力学行为对柔性电子性能影响的内在规律，突破现有喷印制造的极限分辨率和极限频率，为提高柔性电子喷印制造水平提供理论基础和技术支撑，最终实现助力增强我国柔性电子制造核心竞争力的目的。

Flexible electronics have reinvigorated numerous emerging application areas such as foldable display as well as precision and wearable medical devices. Inkjet printing is ideal for manufacturing flexible electronics because it is a maskless and direct-write process that can fabricate circuits on large and flexible substrates. The ink used in printing flexible electronics is highly viscous and non-Newtonian fluid which consists of solvent and active contents of isotropic 1D or 2D functional nanomaterials. However, the very limited study and knowledge on the generation and impact dynamics of micrometer-sized non-Newtonian fluid droplet hinders the further improvement of printing resolution and throughput. Based on the special rheology property of the new functional inks and the high shear rate of impacting of micrometer-sized droplet, this proposal will investigate the droplet impact dynamics in the parameter space of 100 ns second time scales, micrometer length sales, and 10 MHz shear rates. The project has the following objectives: to discover new impact phenomenology of micro non-Newtonian fluid droplet; to explore the new rheology behavior and its effect on droplet expansion; to establish new model that describes the interplay between intense shear flow and the alignment and aggregation of the functional material elements of inks; uncover the effects of key fluid dynamics process on the performance of printed flexible electronics; and overcome the limitation of resolution and frequency of current inkjet printing technology. The results from this project are expected to provide fundamental understanding as well as enabling technologies for more advanced flexible electronics manufacturing. The outcome of the project is eventually beneficial for making the flexible electronics manufacturing industry of China more globally competitive.