用晶格Boltzmann方法研究功能性微气泡生成机制

Microbubble is a new development trend in medical and biomedical domain because it is an integrated functional platform for doal-mode ultrasound(US)/magnetic resonace imaging(MRI) as well as the targeted delivery of genes and various drugs. People have carried out a series of research work that revolved around functional microbubbles. However, microbubbles that are useed as therapeutic agents for human use need to meet the strict demand about its diameter size, the uniformity of diameter, its stability and security, up to now, there are still some fundamental problems have not been resolved, such as how to effectively generate functional microbubbles to meet the demand of medical applications, and so on. In this project, a lattice Boltzmann model for studying generation process of functional microbubbles will be developed. By using of the high-performance techonology, the process that particles of drug had been absorbed on the gas-fluid surface in microchannel is simulated, and the rule of absorption is investigated, a better understanding of loaded drugs on the surface of microbubbles can be gain. By simulating the complex process of coatings bubbles with multilayer of liquids immiscible, the influence of the structure of microhannel with hierarchical structure, the roughness and wettability of the wall in microchannel is investigated, in order to provide the theory instruction for designing and developing fine control device for medical functional microbubbles.

集早期诊断和靶向治疗于一体的功能性微气泡已成为目前生物医学应用领域的一个发展新趋势，人们围绕功能性微气泡的制备开展了一系列的研究。然而，由于用于人体内的治疗剂对微气泡的直径大小、均匀性、稳定性及安全性有严格的需求，迄今为止，生成功能性微气泡的技术仍然面临着许多挑战性的问题，如：如何更精确地控制药剂在微泡中的装载；如何更有效地产生符合医学应用的多层包膜微气泡等等。本项目拟采用基于介观的晶格Boltzmann方法，借助高性能计算技术，对微通道内药物颗粒在气泡表面吸附过程进行模拟，探索药物颗粒吸附规律，获得对微气泡表面装载药物规律的深入认识；对复杂的多层包膜微泡生成过程进行模拟，研究多级嵌入微通道结构及通道表面特性对多层微泡生成的影响，以期为发展可控医用的微气泡生成装置提供理论指导。

为了精确控制功能性微气泡的生成，本项目基于多相晶格Boltzmann模型，借助高性能计算技术，探索药物颗粒的吸附规律及微管道对微气泡生成的影响。本研究已在多相流模型、动态接触线建模、管道内微气泡生成建模及模型的并行实施等多个方面取得进展。. 多相流晶格Boltzmann模型是模拟功能性微气泡生成的重要工具。基于自由能理论，为了避免复杂的压力张量的计算，通过导出状态方程与压力张量计算的关系，得到了更简单、高效的同时满足热力学一致性和伽利略不变性的大密度的多相流晶格Boltzmann模型，该模型可适用各类单组分多相系统，具有很高的应用价值。. 微管道内功能微气泡生成建模需要准确描述相间界面的动态迁移。以细支气道内气溶胶生成为例，基于多相流晶格Boltzmann模型实现了相界面的自然演化，再现了三种液塞在管道内运动及断裂过程，尤其是断裂过程中微液滴生成的过程。该模型能有效处理多相流中液滴生成过程的相界面变化，可以扩展到复杂微管道内气泡生成的研究。. 动态接触线建模是模拟和分析在微气泡生成机制中的管道壁面和颗粒表面的润湿性影响的重要部分。采用基于扩散界面的多相流晶格Boltzmann模型实现了动态接触线的建模，并通过润湿边界条件实现液-固相间相互作用的描述。基于该方法，我们对异构表面上的三相接触线解钉行为及受力进行了分析。. 多相流模型中涉及的梯度计算严重影响了该模型的并行算法性能。基于CUDA的GPU高性能技术，考虑梯度运算的并行实施，采用交叉分块技术、粒子群算法及核融合优化设计等多个策略提出了多相流晶格Boltzmann模型算法的并行实施方案，使得三维GPU算法并行性能比CPU+OpenMP算法提高了60倍。