Machine Learning-Informed Predictive Design and Analysis of Electrohydrodynamic Printing Systems

Electrohydrodynamic (EHD) processes are promising techniques for manufacturing nanoscopic products with different shapes (such as thin films, nanofibers, 2D/3D nanostructures, and nanoparticles) and materials at a low cost using simple equipment. A key challenge in their adoption by nonexperts is the requirement of enormous time and resources in identifying the optimum design/process parameters for the underlying material and EHD system. Machine learning (ML) has made exciting advancements in predictive modeling of different processes, provided it is trained on high-quality datasets at appropriate volumes. This article extends the suitability of such ML-enabled approaches to a new technological domain of EHD spraying and drop-on-demand printing. Different ML models like ridge regression, random forest regression, support vector regression, gradient boosting regression, and multilayer perceptron are trained and their performance using evaluation metrics like RMSE and R2_score is examined. Tree-based algorithms like gradient boosting regression are found to be the most suitable technique for modeling EHD processes. The trained ML models show substantially higher accuracy (average error < 5%) in replicating these nonlinear processes as compared to previously reported scaling laws (average error ≈ 42%) and are well suited for predictive modeling/analysis of the underlying EHD system and process.     

电磁致动式微滴按需喷射装置的设计及实现

针对现有商业化微滴按需喷射装置需根据喷射材料性质定制而较难直接用于研究不同材料喷射行为的现存问题,设计并实现了一种基于电磁致动器的机械振动式低成本微滴按需喷射装置。该装置由激振系统,喷射坩埚及相应的低氧环境保护系统,加热及温度控制调节系统组成。采用该微滴喷射装置进行试验,通过调整电磁致动器激励电压脉宽成功实现了不同喷射频率下水和石蜡微滴的按需可控喷射,试验结果证明了该装置的稳定性以及实现不同材料微滴喷射的可行性。     

气动式微滴喷射中液滴稳定生成的动力学特性研究

微滴喷射增材制造技术作为制造领域的新兴前沿技术有着广泛的应用前景,微滴生成特性对增材制造中微滴在基板铺展、搭接、凝固等过程影响较大,研究微滴生成特性对于提高液滴生成尺寸、频率和稳定性有重要意义。通过试验研究气动按需喷射作用下的微滴喷射行为,探究喷嘴尺寸、黏度和供给压力等因素对射流断裂过程及液滴生成稳定性的影响关系,并进一步研究形成角的变化对液桥断裂顺序及卫星液滴产生的影响关系。研究结果表明,随着喷嘴直径减少,韦伯数（We）显著减少,当喷嘴直径减少到100 μm时,We变为0.33,液滴尺寸与喷嘴直径的比值急剧增大;随着黏度的增加,射流颈缩段的液桥显著增长,液滴尺寸明显增大。在保证生成单个液滴的压力条件下,当供给压力较小时,液桥两端先后断裂形成卫星滴,并最终与半月面融合;随着压力的增大,液桥只发生一次断裂,剩余射流回缩到喷嘴内。在气动式喷射方式中由于上形成角始终大于下形成角,所以液桥总是在靠近液滴端首先断裂,该研究结果有助于提高气动式微滴喷射装置的液滴生成质量。     

Potentials and challenges in jetting microdroplets onto nonwoven fabrics

Nonwoven fabrics are very diverse in their structural properties. This paper discusses potential opportunities and challenges involved in jetting and depositing microdroplets on such materials. This study reports on the interaction of controlled droplets with the nonwoven substrates. Droplets used had velocities of about 1.8 m/s and diameters of about 90 μm and were produced by using a drop-on-demand (DOD) inkjet printhead. Nonwovens used consisted of two groups of high and low solid volume fraction (SVF) substrates. The results indicate that in the case of low-SVF nonwovens, the local spacing and orientation of the fibres plays a significant role in determining the outcomes of the jetting process. Drops were seen to penetrate deep into a low-SVF nonwoven and deposit on a single fibre or bundle of fibres. Low-SVF nonwovens, therefore, can hold the fluid within their structures—a case of interest in printing electric circuits. The case of jetting on high-SVF nonwovens was found to be primarily dependent on the fibres' surface properties. The drops were found to stay above the surface in the case of hydrophobic fibres and below the surface in the case hydrophilic ones.     

气动膜片式微滴喷射装置理论分析与实验研究

微滴喷射是通过产生微米级的液滴实现流体按需精确喷射沉积成形的技术。气动膜片式微滴按需喷射装置的原理是以膜片为驱动部件,以压缩气体脉冲为驱动源,通过膜片的弹性变形实现液体腔的体积变化从而产生微液滴。通过建立驱动气压与液体腔内工作压力的关系,分析腔体内液体的流动状态,从而建立气动膜片式喷射系统的数学模型,以此作为优化装置结构和控制参数的依据。此外,利用该装置完成了黏性液体的可控喷射。研究结果为喷射制造的实际应用提供了理论与实验依据。     

值得关注的“全印制电子技术”

文章概要指出,目前正在兴起的全印制电子的优点,它将得到迅速的发展,并将成为PCB生产的革命性进步和主流技术。     

Effect of process parameters on copper droplet ejecting by pneumatic drop-on-demand technology

Stable generation of copper droplets is a key issue in fabricating copper parts by drop-on-demand (DOD) technology. The process parameters such as supply pressure and electronic pulse width have significant effect on pressure variation and droplet formation. In the present work, a pressure acquisition system was first set up to measure the pressure variation in crucible. Then the measured pressure data were applied on a 2D axisymmetric model as inlet conditions to study the influence of process parameters on copper droplet formation. The results indicated that the peak pressure in crucible increased linearly with the increase of supply pressure. As supply pressure increased, the jet velocity and the limiting length increased to critical value and droplet could be generated. The peak width increased with the rise of electronic pulse width. By increasing the electronic pulse width, the time of pressure above threshold value increased and the jet limiting length grew to critical value for breakup. However, if supply pressure and electronic pulse width were too large, satellite droplets would be formed. Pure copper droplet generating experiments were conducted to obtain appropriate parameters. Single droplet was generated while supply pressure was between 60 kPa and 100 kPa and pulse width was between 550 μs and 1550 μs. Also the range of pulse width varied as the supply pressure increased for generating single droplet. The statistics of droplet diameter suggested that droplet diameter increased with the increase of supply pressure. Electronic pulse width had influence on the droplets size and the standard deviation increased with the increase of electronic pulse width. So small supply pressure and electronic pulse width should be used for generating uniform droplets.     

低温冰型快速成形技术中喷射技术研究

低温冰型快速成形技术是一种基于喷射成形的快速成形工艺，喷射技术是其工艺关键，在工艺的开发和研究中，先后采用了连续喷射和离散喷射2种方式的喷头，总结了实验当中2种喷射方式在出流阈值，流量，稳定性，精密性，响应灵敏度等方面表现的差异，从喷头结构和喷射原理两方面对2种喷方式的差异进行了理论分析，阐述了离散喷射和连续喷射2种方式的特点，指出了2种喷射方式各自的使用领域。     

微流体数字化技术制备聚合物微透镜阵列

基于微流体数字化技术搭建了聚合物微透镜阵列按需喷射制备实验系统。以UV固化胶为喷射材料,将其按需喷射到镀有疏水化薄膜的玻璃基片上,在界面张力和疏水化效应的作用下,形成平凸状的微液滴,再经紫外光固化后形成微透镜阵列。实验研究了系统参量对稳定微喷射与微透镜直径的影响,稳定微喷射出了黏度值为50×10-3 Pa·s的UV胶,制得了最小直径达25μm的微透镜,进而制备出了直径变异系数C·V达0.64%、焦距均匀性误差为1.7%的15×15微透镜阵列。微透镜在扫描电子显微镜下具有较好的表面形貌,采用白光干涉/轮廓仪(VSI模式)测得其轮廓算术平均偏差Ra为247.99nm(扫描区域:29.4μm×39.3μm),扫描区域轮廓曲线平滑。通过微透镜阵列的成像实验,得到了微透镜阵列所成的清晰实像。实验结果表明,采用微流体数字化技术进行聚合物微透镜阵列的按需喷射制备过程简单、成本低廉、工艺参数稳定;制备的微透镜阵列几何与光学性能优越。     

喷墨打印机及其耗材技术现状与进展

喷墨打印是一种快速发展的高新信息技术，在非接触性打印领域占有重要地位。喷墨打印机用墨水和介质，也随打印机技术的改进不断更新换代。本文综述了喷打印器件、打印介质、打印墨水发展的基本情况，着重探讨了喷墨打印技术新用途的广阔前景，介绍了喷墨打印技术的发展趋势。