【作者】 谢丹；

【导师】 张鸿海； 刘胜；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 近代光学和光电子技术的迅猛发展使光电子仪器及其元件发生了巨大的变化,微型化和智能化成为实现这一变化的主要发展方向,由此诞生了一门崭新的学科——微光学(micro-optics)。微光学器件在几乎所有的工程应用领域,尤其在现代国防科技领域中有重要的应用价值和广阔的应用前景。然而,微光学器件的实际制作水平远远落后于理论设计水平,加工问题已成为阻碍其迅速发展和应用的巨大障碍。因此,针对微光学器件制作的高效率、大批量、低成本制造技术是各国学者竞相研究的重要课题。微滴喷射是一种通过产生微米级的液滴实现微量流体精确分配的技术,属于非接触直写式制作技术的范畴,作为一种增材式制造方法,它不仅可以节约材料、减少工艺步骤、提高生产效率,而且具有极好的环境兼容性,并能与计算机控制紧密结合,直接喷射制作复杂的三维结构,可以满足未来制造技术的发展对环境保护、材料利用率以及工艺灵活性等诸多方面的要求。本文提出了一种具有自主知识产权的用于微光学器件制作的气动膜片式微滴喷射技术。该技术融合了压电喷射装置和气压直接驱动装置的优点,具有结构简单、操作维修及拆卸方便、驱动功率大以及可靠性优良的特点。本文在构建气动膜片式微滴喷射平台的基础上,进行了气动膜片式喷射机理及实验研究,所做的工作阐述如下：首先,以膜片模态、载荷-挠度特性、膜片与液体的固-液耦合关系为理论基础,运用非平衡伯努利方程和质量守恒方程建立了气动膜片式喷射过程的数学模型,获得输入气压与膜片变形、腔内压力以及喷嘴出口流体速度的关系,并以此作为优化微喷射装置结构参数和控制参数的理论依据。其次,构建了包括微喷射装置、电磁阀驱动系统、压力控制系统、温度控制系统、图像在线监测系统及精密运动平台的气动膜片式微滴喷射系统。重点研究了玻璃喷嘴的可控制作技术和基于延时触发的图像采集与处理系统。该系统可用来获取微液滴喷射形成和沉积成型过程的图像信息,运用数字图像处理方法计算出液滴大小、飞行距离与速度。接着,基于Fluent 6.3中的VOF模型模拟了喷射形成主液滴及卫星滴的全过程,探讨了微液滴形成的规律。利用喷射平台进行了微液滴喷射的一致性分析,研究了设备结构参数及控制参数与液滴大小及喷射速度的关系。此外,以不同物理性质的溶液为对象进行了粘度及表面张力对液体喷射过程影响的实验研究。然后,利用能量守恒的分析方法对微液滴碰撞基板后的各个过程进行理论研究,运用反弹阈值公式根据微液滴碰撞前的初始条件判定碰撞后的变形状态。此外,通过实验方法得到不同物理性质的微液滴在多种润湿性基板上的沉积过程,并分析了液滴物理性质、液滴与基板的相互作用对微液滴沉积过程的影响,为喷射制作中的沉积过程提供了理论与实验依据。最后,利用紫外固化胶完成了直径为75-400μm微透镜阵列的制作。对平均直径为333.28μm的9x9微透镜阵列进行检测,其尺寸偏差约为1.6%,表面平均粗糙度约为0.243nm,焦距计算平均值为389.07μm、均匀性误差为1.6%,利用玻罗板测得焦距平均值为482.04μm、均匀性误差为1%,结果表明微喷射方法用于制作微光学器件具有很大的灵活性和极大的发展潜力。此外,附录中还介绍了一种适用于聚合物微光学器件复型制作的微压印技术。分别探讨了采用接触式压印技术制作光栅和采用非接触式压印技术制作微透镜阵列的方法。结果表明,微压印技术是完成聚合物微光学器件高效率、大批量、低成本制作的良好方法,具有较大的研究价值和广泛的应用领域。更多还原

【Abstract】 Along with the rapid development of modern optics and optoelectronic technology, photoelectronic equipment and devices have made significant changes. Miniaturization and intellecturalization have been the main building blocks for realizing the change. A new subject, micro-optics, was born. Micro-optical devices have wide application prospects almost in all engineering applications, especially in the area of defense science and technology industry. However, actual production quality lags far behind theoretical design ability. Manufacturing problem becomes a great barrier to its development and applications. Consequently, fabrication technology aiming at micro optical devicess of high efficiency, low cost and volume production has become one of important research domains in the world. As one of precision fluid dispensing techniques, micro-droplet jetting indicates a fabricating process which is used to precisely dispense functional and/or structural materials on a substrate in digitally defined locations. Being a material increase manufacturing (MIM) technology, it belongs to the domains of direct writing technology. It can not only simplify processing steps and improve productivity, but also lower consumption of energy or raw materials. Furthermore, it posess better environmental compatibility. As an additive fabrication technique of data-driven type, it can directly manufacture complicated 3D structures. The progress of the technology meets the needs of environmental protection, material utilization and technical flexibility for the development trend of modern manufacturing process.A pneumatic diaphragm-based Drop-on-Demand (DOD) microdroplet jetting technology with independent intellectual property right is presented in this dissertation. Combining the advantages of piezoelectric and pneumatic generators, the pneumatic diaphragm-based DOD generator has the following key features:simple construction, convenient operation and maintenance, large driving power and robust. The self-developed pneumatic diaphragm-based DOD system is set up and used to complete the studies on principle and fabrication technique of microdroplet jetting. And the main contents are summarized as follows:Firstly, the mathematical model of jetting process of the pneumatic diaphragm actuator is carried out by unsteady Bernoulli equation and mass conversation equation based on analysis of diaphragm modal, load-deflection characteristics and fluid-diaphragm coupling. The relationships between the input pneumatic pulse and diaphragm deformation, internal pressure of chamber, nozzle and throttle outflow velocity were attained. The model and calculation results may be used as theoretical basis for structure and control parameters optimization of jetting generator.Secondly, the pneumatic diaphragm-based DOD microdroplet jetting system is set up, including several units:the generator, solenoid valve driving circurt, pressure control unit, temperature controller, the 3-dimensional working platform and the in situ vision subsystem. The research emphasises on the controllable making method of glass nozzle and the in situ vision system. Delayed external trigger is put to stir up the CCD to capture images. The droplet dimension, flying distance and velolcity can be caculated from these images through digital image processing.Thirdly, in order to discuss the mechanism to form microdroplet, the formative process of primary droplet and satellite droplet is simulated using VOF model by Fluent 6.3. The performance of the generator was studied by adjusting the structure and control parameters. Furthermore, the influence of fluid properties on the droplet ejection process was experimentally investigated.Next, the post-impact micro droplet deformation processes, from spreading and recoiling, to either oscillation of rebound are described in detail and an analytical expression of the energy state at each discrete stage is presented. Bouncing criterion coming from energy conservation can be used to determine the deformation state after impacting through initial condition of microdroplet. Furthermore, the post-impact processes of different physical properties microdroplets on substrate of different wettability were obtained. The influence of micro droplet characteristics and the interaction of micro droplet and substrate on post-impact process afford key theoretical and experimental proof for jetting technology.Finally, micro-lens arrays with 75-400μm in diameter, were produced by UV curing glue. Through testing 9x9 micro-lens array with diameter of 333.28μm, the results indicated that the variation of diameter is about 1.6%, surface roughness is about 0.243nm, the calculated mean focal length is aout 389.07μm, the uniformity error is 1.6%, the measured mean focal length by Porro reticle is 482.04μm, the uniformity error is 1%. The experimental results demonstrate that the jetting technology is a quite potential and very flexible manufacture method for micro-optical devices.In addition, a micro hot embossing technoloty suitable for polymer micro-optical devices replication methods are also studied. Micro grating is fabricated by contact-type embossing method, while micro-lens array is fabricated by contactless embossing process. The results indicate that micro hot embossing technology is an excellent manufacture way in batch quantity with high-efficiency and low cost and shows a good application prospect.更多还原