微通道内可变压多腔室微胶囊流变问题的数值与实验研究

Multicompartmentalized capsules with multiple pressure-changable sub-capsules, which could encapsulate multiple independent components and release them in a controlled manner. They are also fine models to mimick the living cells with complex internal structures. Thus, they are hot spots of the study of soft particle matters in recent years. Micro-capsules are generally in a flow environment. Thus, their deformation and breakup under shear forces have become the important research direction of rheology and fluid mechanics. However, as the internal structures of multicompartmentalized pressure-changable capsules are very complicated, and as their rheological behaviors involve the pressure change and the complex mechanical features of their elastic membranes, up to now the study to them is only limited to the simplest structure, the capsule with a single compartment without any pressure change. By employing the similarity between multicompartmentalized capsules and multiple emulsions, this project introduces the boundary integral equation published lately for multiple emulsions. By changing the boundary conditions of interface tensions for multiple emulsions to that including pressure term and elastic tensions of membranes for capsules, this project will develop a novel numerical method for multicompartmentalized pressure-changable mico-capsules. By using this algorithm and relevant experiments, this project will study the relation among the rheology of capsules, internal structures (especially asymmetric structures), internal pressure of each compartment and mechanical features of membranes. This project will disclose the possibility of the occurrence of contolled asymmetric breakup and controlled cascade reaction of micro-capsules through the flow shear. Finally, through the adjustment of the membrane, internal structures and pressure of each compartment, this project will try to realize the scientific design of soft particles based on some specific goals such as the targeted transportation and release of the active ingredient.

可变压多腔室微胶囊包含若干内压可调的子胶囊，可实现不同组分的独立贮存与控制释放，同时是细胞研究的近似模型，因而成为当前软颗粒研究的世界热点。微胶囊通常处于流体中，这样其受剪切而发生变形破裂就成为流变学的重要研究方向。然而，由于这种微胶囊内部结构复杂，其流变又涉及各腔室压力变化及弹性膜的复杂力学特性，因而目前研究仅限于单腔室无压变这一最简单情况。本课题利用多腔室微胶囊与复杂乳液间的相似性，引入用于研究复杂乳液的边界积分方程，并将原界面张力边界条件改为包含压力和膜力学性质的边界条件，发展出适合可变压多腔室微胶囊流变问题的数值算法。利用该算法和实验，研究胶囊内部结构（尤其是非对称结构）、各腔室压力、膜力学特性与其流变间的作用关系，揭示经由流体剪切，微胶囊发生可控非对称破裂及可控级联式反应的可能。最终通过对弹性膜、多腔室内部结构及压力的调整，实现基于特定目标（例如靶向传递释放）的软颗粒的科学设计。

近年来, 具有复杂内部结构的软颗粒，尤其是可变压多腔室微胶囊，由于在食品、化妆、节能以及靶向药物传输等领域有众多的潜在应用，同时又是细胞研究的简化模型，因此得到了迅猛的发展。复杂软颗粒，例如可变压多腔室微胶囊，以及以之为模型的生物细胞，一般都存在于流体环境中。这样，它们对周围微流场的流变响应就一直是学术界的重要研究方向。近二十年来，微流体技术快速发展，目前日趋成熟。这样，利用微流体技术来研究复杂软颗粒在流场中的流变行为就变得非常自然。本课题利用可以描述多重界面相互作用的更普遍化的边界积分方法，对具有复杂内部结构（尤其是非对称结构）的软颗粒在微流场下的流变响应进行了研究。并以之为基础，调查了软颗粒内部非对称结构对其流变行为（变形、定向移动等）的影响，深入探索了力学作用机理。发现外部非对称拖曳力与内部非对称压力分布及环流的共同作用，导致了软颗粒的非对称变形以及定向偏移，为实现基于特定目标的软颗粒内部结构的设计提供了重要的科学知识。同时，还利用微流体技术对复杂软颗粒的流变行为进行了实验研究，调查了内部结构，压力以及膜性质对流变行为的影响，发现流体对多腔室微胶囊的弹性膜具有剪切作用，造成软颗粒变形并使外膜发生褶皱, 内部压力越大，膜弹性越大，则变形与褶皱越小。本课题定义了褶皱度的新计算方法，当褶皱较大时，可利用其生成多层微胶囊。这些结果对新型复杂软颗粒的制备具有很好的指导意义。