Collaborative Research: Dynamic Control and Separation of Microparticles in Fluids using Optical Whispering Gallery Mode Resonant Forces

这个项目的目标是创造一种新的方法来选择运动控制悬浮在液体中的微米大小的颗粒。这种方法是基于在某些结构中观察到的“窃窃私语廊”共振的光学对立物，即在某一点发出的声音在某些特殊位置可以清楚地听到，即使在其他地方可能听不到。在这个项目中，一个悬浮的球形粒子扮演了耳语廊的角色，其共振由其直径和相对于周围液体的光学特性决定。波长与窃窃廊共振相匹配的激光将对粒子施加明显的光力，而直径略有不同的粒子则不会受到影响。这使得基于尺寸和光学特性的极具选择性的颗粒操作和分离成为可能，从而实现紧凑而坚固的微光流体设备，用于工业，医疗保健和环境应用。该项目将吸引本科院校戈登学院（Gordon College）的学生参与最先进的合作研究，并推动以本科生为重点的研究基础设施的发展。戈登学院的本科生将在光学、微加工、微流体和控制方面发展实际的专业知识。该项目还将吸引来自波士顿大学的研究生，这是一所主要的研究型大学，他们将获得宝贵的教学和研究指导技能。该项目将研究一种分离方法，利用光波导周围的倏逝光场对流场中携带的微粒施加力。这些微粒子具有低语廊模式共振，已知强烈依赖于粒子的形状和大小，确保了具有狭义几何特征的粒子的前所未有的选择性。仔细控制作用力和流速可以设计颗粒轨迹，将选定的颗粒引导到储层中以完成分离。为了提高吞吐量，将利用网络控制系统模型，设计通信和控制策略，利用单个驱动通道同时引导不同特定尺寸的颗粒。该项目的方法有几个令人满意的方面：它具有精致和可调的选择性；适用于固体颗粒和悬浮液滴；并可用于小型、坚固的微光流控装置。这项工作将在几个方向上推进基础科学和工程。它将提供详细的光推进力的参数研究，由于窃窃私语画廊模式共振，并有助于发展的现象的基本理解。颗粒分离应用允许在各个领域有用的技术的发展，同时也提供了一个设置，以发展网络控制理论领域。由于使用单个致动器来控制多个粒子的运动，因此这项工作需要网络控制理论的新应用，以及探索和解决该领域挑战的新领域。该研究还将推动实验流体动力学和光学科学的边界，导致微型光流体装置的制造和测试。

The objective of this project is to create a new method for selective motion control of micrometer-sized particles suspended in liquids. The method is based on an optical counterpart to "whispering gallery" resonance observed in certain structures, in which a sound made at one point may be heard clearly in certain other special spots, even though it may be inaudible everywhere else. In this project, a suspended spherical particle plays the role of the whispering gallery, with the resonance determined by its diameter and optical properties relative to the surrounding liquid. Laser light with wavelength matched to the whispering gallery resonance will apply significant optical forces to the particle, while particles of even slightly different diameters will feel no effect. This allows extremely selective particle manipulation and separation based on size and optical characteristics, enabling compact and robust micro-opto-fluidic devices for use in industry, healthcare, and environmental applications. The project will engage students from Gordon College, an undergraduate institution, in state-of-the-art collaborative research and advance the growth of an undergraduate-focused research infrastructure. Gordon College undergraduates will develop hands-on expertise in optics, microfabrication, microfluidics, and control. The project will also engage graduate students from Boston University, a major research university, who will obtain valuable teaching and research mentoring skills.This project will investigate a method of separation using evanescent optical fields around an optical waveguide to exert forces on microparticles that are being carried in a flow field. These microparticles possess whispering gallery mode resonances that are known to be strongly dependent on the shape and size of the particles, ensuring an unprecedented selectivity of particles with narrowly defined geometric characteristics. Careful control of the forces and flow velocities allows for the design of particle trajectories, directing the selected ones into reservoirs to accomplish separation. To increase throughput, a networked control system model will be leveraged and communication and control policies designed that leverage the single actuation channel to simultaneously steer particles of different specific sizes. The project's approach has several desirable aspects: it has exquisite and tunable selectivity; it is applicable to solid particles as well as suspended liquid droplets; and it can be used in a compact and robust micro-opto-fluidic device. This work will advance fundamental science and engineering in several directions. It will provide detailed parametric study of the light propelling forces due to whispering gallery mode resonances and help to develop a fundamental understanding of the phenomenon. The particle separation application allows for the development of technology useful across various fields while also providing a setting to develop the field of networked control theory. Because a single actuator is employed to control the movement of multiple particles, this work requires a novel application of networked control theory and a new domain for exploring and resolving challenges in this field. The research will also push the boundaries in experimental fluid dynamics and optical science leading to the fabrication and test of a micro-opto-fluidic device.