微通道射流加工滞止区的磨粒动态冲击效应研究

Microfluidics technology characterized by the micro-channel network employs the microfluidic chips to activate and control the flow in order to realize their special and unique functions by combining with other technologies, such as microelectronics, optics, energy and biomedicine. The machining quality of high width-depth ratio micro-channels on the hard brittle substrates would affect their performance and stability in application. In order to improve the efficiency and quality in machining of micro-channels on microfluidic chips, a new method by considering the particle dynamic impacts in the stagnation zone with an assistance of ultrasonic vibration on the workpiece during the abrasive slurry jet (ASJ) micro-channeling process is proposed in this project. Firstly, by introducing the ultrasonic vibration-assisted machining, it is to investigate the coupling effect of the vibration and ASJ flow on the particle distribution, particle impact velocity and impact angle in the stagnation zone as well as the machining quality both numerically and experimentally. Then, the material removal mechanism under the dynamic impacts of abrasive particles on the hard brittle materials will be analyzed using discrete element method to explore the effect of vibration on the initiation, propagation and intersection of subsurface micro-cracks and using experimental study to observe the surface damage in the impact erosion zone, which in turn contributes to the improvement of the ASJ micro-machining ability. Finally, the effect of the process parameters on the major micro-channeling performance and machining quality will be experimentally investigated, and the associated mathematical models would be developed as well to predict the ASJ micro-channeling performance and its machining quality that can be used to offer an optimized selection of process parameters for industrial purpose.

以微通道网络为结构特征的微流体技术是使用微流控芯片来控制和利用流体，实现微米尺度上与微电子、光学、能源、生物医学等领域相结合的新兴技术，而以硬脆材料为基底的微流控芯片中高宽深比微通道的加工质量将影响它在应用中的性能和稳定性。本项目面向微流控芯片中高宽深比微通道高效和高质量的加工要求，提出一种基于射流滞止区磨粒动态冲击效应的微细磨料水射流加工高宽深比微通道的方法。通过引入超声辅助加工，建立工件振动和微细磨料水射流流场的耦合模型，研究耦合作用下射流滞止区内磨粒的动态冲击对微细磨料水射流加工质量的影响；采用离散元仿真结合试验研究揭示硬脆材料在磨粒动态冲击效应下的去除机理，为提高微细磨料水射流的加工能力提供理论依据；试验研究微细磨料水射流在不同工艺组合参数条件下加工高宽深比微通道的工艺过程，建立相关的数学模型并实验验证，提出工艺优化策略和加工质量评价指标，实现高宽深比微通道高效和高质量的可控加工。

以高强度、高耐磨性和高耐腐蚀性为特点的硬脆材料衬底上加工具有高宽深比的微通道被广泛应用在燃料电池、微传感器、微生物芯片等微流体器件的设计中。作为微流体的流动通道，微通道的加工质量将影响微流体的流动特性，从而影响微流体器件的性能和稳定性。因此，加工制备高质量的微通道对推动微流体技术的发展有重要意义。本项目采用CFD-DPM耦合的数值模拟方法研究了超声振动场与微细磨料水射流流场的耦合作用，探索了超声振动对水射流滞止区、磨粒冲击速度和角度的影响规律，揭示了射流滞止区内磨粒动态冲击效应，并通过相关实验验证了数值模拟的结果。以玻璃试样为研究对象，试验研究了超声振动辅助加工下微细磨料水射流冲蚀硬脆材料的去除机理，总结了冲蚀角度、磨粒大小、射流压力、振动频率等工艺参数对材料去除的影响规律。最后通过实验研究了加工工艺参数与微通道结构以及底面粗糙度的关系，建立相关的数学模型并实验验证，并提出工艺优化策略。本项目得相关成果为超声辅助微细磨料水射流加工高深宽比微通道的研究提供技术和理论依据。