Active emulsions: Magneto-capillary dynamics of particles at curved interfaces

油和水不能混合;然而，通过稳定它们之间的界面，一种小液滴可以分散在另一种中。这些所谓的乳液通常存在于食品，化妆品和药物中，其中亲油分子和亲水分子的混合物必须一起工作才能正常工作。表面活性分子和颗粒-称为表面活性剂-吸附在油-水界面，以稳定乳液并防止不混合。该项目旨在创建磁性表面活性剂，其使用外部磁场为动态功能提供动力，例如在单个乳液液滴水平上的混合和推进。该项目将研究吸附在弯曲界面上的颗粒的磁驱动运动及其在微米级泵送流体中的应用。所得的活性乳剂对于加速和/或控制药物递送速率或复杂流体内的化学反应是潜在重要的。除了为研究生和本科生提供研究培训外，该项目还将为来自不同背景的初中和高中学生提供教育推广。研究人员将与内部工程计划合作，为曼哈顿和布朗克斯附近学校的学生开发和实施实验室参观课程。通过动手示范和主动学习策略，该计划旨在让学生对科学探究和工程设计的过程感到兴奋。通过将磁力矩耦合到弯曲界面的毛细力，使均匀场中的快速粒子运动成为可能。基于最近对这些磁毛细管动力学的演示，该项目将研究随时间变化的磁场如何驱动液滴内部和周围的复杂颗粒运动和界面流动。该项目旨在（1）了解驱动场的波形和磁性颗粒的特性如何在弯曲界面上引导它们的动态运动;（2）量化颗粒运动引起的乳液液滴内部和周围的瞬态流体流动;（3）识别特定的颗粒类型和驱动协议，以优化所需的功能，如增强传质和推进液滴运动。这些目标将通过粒子/乳液系统的实验和磁毛细管粒子动力学和流体流动的建模相结合来实现。该项目将研究如何利用这些场诱导流来增强质量传递和推动液滴运动。与宏观乳液的批量处理相反，活性乳液内的分布式致动将使多相流体内的工程反应动力学、传质和分离的新策略成为可能。为了实现这些功能，将开发和部署贝叶斯推理、实验设计和优化的自动化工具，以有效探索可能的驾驶领域。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Oil and water don’t mix; however, by stabilizing the interface between them, small droplets of one can be dispersed in the other. These so-called emulsions are commonly found in foods, cosmetics, and pharmaceuticals where mixtures of oil-loving and water-loving molecules must work together to function properly. Surface-active molecules and particles - termed surfactants - adsorb at oil-water interfaces to stabilize emulsions and prevent unmixing. This project aims to create magnet surfactants that use external magnetic fields to power dynamic functions such as mixing and propulsion at the level of individual emulsion droplets. The project will investigate the magnetically driven motions of particles adsorbed at curved interfaces and their use in pumping fluids at the micron-scale. The resulting active emulsions are potentially important for accelerating and/or controlling the rates of drug delivery or chemical reactions within complex fluids. In addition to research training for graduate and undergraduate students, the project will provide educational outreach to middle and high school students from diverse backgrounds. In collaboration with the Inside Engineering initiative, the researchers will develop and implement a laboratory visit curriculum for students from nearby schools in Manhattan and the Bronx. Through hands-on demonstrations and active learning strategies, the program aims to get students excited about the processes of scientific inquiry and engineering design.Rapid particle motions in uniform fields are made possible by coupling magnetic torques to capillary forces at curved interfaces. Building on recent demonstrations of these magneto-capillary dynamics, the project will investigate how time-varying magnetic fields can drive complex particle motions and interfacial flows within and around liquid droplets. The project aims (1) to understand how the waveform of the driving field and the properties of the magnetic particles direct their dynamic motions on curved interfaces; (2) to quantify the transient fluid flows within and around emulsion droplets induced by particle motions; and (3) to identify specific particle types and driving protocols optimized for desired functions such as enhancing mass transfer and propelling droplet motions. These aims will be achieved through a combination of experiments on particle/emulsion systems and modeling of magneto-capillary particle dynamics and fluid flows. The project will examine how these field induced flows can be harnessed for enhancing mass transfer and for propelling drop motions. In contrast to bulk processing of macroscopic emulsions, distributed actuation within active emulsions will enable new strategies for engineering reaction kinetics, mass transport, and separations within multiphase fluids. In pursuit of these functions, automated tools for Bayesian inference, experimental design, and optimization will be developed and deployed to enable the efficient exploration of possible driving fields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.