Designer Soft Microparticles for a Changing Environment

非技术摘要直径数十至数百微米的聚合物颗粒和胶囊，类似于人头发的大小，被广泛用于对化学或环境敏感的活性分子或纳米颗粒的封装和保护，其用途例如用于食品和洗涤剂添加剂、化妆品以及药物输送。在储存和运输过程中，密封剂保护货物，并将其释放到所需的位置，这通常是通过一些外部刺激来破坏或降解密封剂。微胶囊是具有薄壳和大空芯的颗粒，特别有价值，因为只需要少量的包封剂就可以保护大量所需的有效载荷。在这个项目中，开发了具有壳的新型微胶囊，该壳可以响应于不同的外部刺激而可逆地释放胶囊内容物，而不破坏壳，使胶囊保持完好以供重复使用或重复开关释放。这些胶囊非常适用于在水中清除废物的应用，在这种情况下，可以打开它们来收集废物，关闭以移除废物，然后重新打开以在适当的存储容器中释放废物。这些胶囊是从复杂的乳状液中获得的，例如水芯油滴，这些乳状液是使用具有与液滴相当大小的通道结构的微流控设备制造的。这项技术使胶囊的精确制造成为可能，可以控制胶囊的大小、外壳厚度和成分，分散度非常低。参与该项目的学生，包括本科生和研究生，都接受了功能聚合物合成、微流控技术和材料表征方面的培训，为他们提供了现代材料科学多学科研究不可或缺的广泛工具。技术摘要化学或环境敏感的活性分子或纳米颗粒的包埋在从食品添加剂到洗涤剂和药物输送的许多应用中都是至关重要的；传统上，牺牲包封剂用于一次性、单向包埋和释放的设计中。该项目的一个主要目标是开发和制造一种基于功能聚合物微胶囊的新型动态包封剂系统，该微胶囊与环境显示出积极和可逆的相互作用。微流控装置用于产生定义明确的不相容流体的多个乳液滴，这些乳液滴形成用于软封装材料的模板。研究了功能材料在复合乳液中组装的物理过程，以及材料本身的动态功能，以及液体限制对这些过程和性能的影响。该项目的另一个目标是研究这些功能性聚合物微胶囊与溶质、环境和外部刺激的相互作用，以响应和选择性地渗透到胶囊内外。具有这种响应性渗透性的胶囊系统能够按需可逆地释放活性物质，并通过触发对货物的摄取和捕获来补充胶囊内的活性物质。本研究将这种胶囊剂的应用范围从单向递送系统扩展到纯化和分离。该项目的另一个目标是开发具有受控机械性能的设计型多孔介质，以研究多孔介质行为的基本机制和其中的多相流。这些模型系统提供了对广泛实践但未被很好理解的过程的洞察，包括压力冲击导致的多孔介质的破裂，以及聚合物溶液对多孔介质中多相流体流动的影响。

Non-technical AbstractPolymeric particles and capsules with diameters of tens to hundreds of micrometers, similar to the size of a human hair, are extensively used for the encapsulation and protection of chemically or environmentally sensitive active molecules or nanoparticles, with uses, for example, for food and detergent additives, for cosmetics, as well as for drug delivery. During storage and delivery, the encapsulant protects the cargo, and releases it at the desired location, often through some external stimulus that breaks or degrades the encapsulant. Microcapsules, particles with thin shells and large hollow cores, are particularly valuable because only small amounts of encapsulant is needed to protect large amounts of the desired payload. In this project, novel microcapsules are developed with shells that release the capsule content reversibly in response to different external stimuli without shell destruction, leaving the capsule intact for reuse or repeated on-off switching of the release. These capsules are ideal for applications such as waste removal in water, where they can be opened to collect the waste, closed to remove it, and reopened to release the waste in appropriate storage containment. These capsules are obtained from complex emulsions, such as water-cored oil drops, that are fabricated using microfluidic devices with channel architectures of comparable size to the drops. This technology enables precise manufacturing of capsules with control over size, shell thickness, and composition with very low dispersity. The students involved in this project, both undergraduates and graduates, are trained in functional polymer synthesis, microfluidic technology, and materials characterization, giving them a broad set of tools that is indispensable for modern multidisciplinary research in materials science. Technical AbstractEncapsulation of chemically or environmentally sensitive active molecules or nanoparticles is crucial in numerous applications, from food additives, to detergents and drug delivery; traditionally sacrificial encapsulants are used in a one-time, one-way encapsulate-and-release design. A primary aim of this project is to develop and fabricate a new class of dynamic encapsulant systems based on functional polymer microcapsules that exhibit active and reversible interactions with their environment. Microfluidic devices are used to create well-defined multiple emulsion drops of immiscible fluids that form templates for soft encapsulation materials. The physics of the assembly of functional materials in complex emulsions, and the dynamic functionalities of the materials themselves, are investigated, as is the influence of liquid confinement on these processes and properties. An additional aim of the project is to investigate the interactions of these functional polymeric microcapsules with solutes, the environment, and external stimuli for responsive and selective permeability in and out of the capsule. Encapsulation systems with such responsive permeability enable the reversible, on-demand release of actives, and allow the replenishment of actives inside the capsules through triggered uptake and trapping of cargo. This research extends the application of such encapsulants from one-way delivery systems to utilization in purification and separation. An additional objective of this project is the development of designer porous media with controlled mechanical properties to study fundamental mechanisms of the behavior of porous media and multiphase flow within it. These model systems provide insight into processes that are widely practiced but not well understood, including the fracturing of porous media due to pressure shocks, and the effects of polymer solutions on multiphase fluid flow in porous media.