EAGER: Collaborative Research: Dynamics of Nanoparticles in Light-Excited Supercavitation

可以在液体中高速推进的纳米颗粒（称为“纳米游泳者”）可以在靶向药物输送、原位诊断和纳米纤维等应用中发挥重要作用。对于这样的应用，控制高速纳米游泳者的方向至关重要。然而，高速的纳米游泳者大多是由随机方向的力推动的，而引导的纳米游泳者目前仅限于低速。 因此，设计完全可控但快速移动的纳米游泳者具有重大的技术潜力。 最近的实验已经观察到，极快（100，000微米/秒）的金纳米粒子游泳者可以通过光作为外部能源来引导。然而，其基本机制尚未完全了解。EAGER项目将通过研究光驱动的纳米粒子的力和能量平衡，迈出理解这一现象的第一步。纳米游泳者运动的实验和数值模拟的结合将提供对纳米游泳者动力学的基本理解，并解决有关其运动的潜在机制的问题。 这反过来将提供新的信息，可以导致广泛的高级纳米工程应用，例如选择性地在表面打印纳米结构用于传感应用或使用皮肤可穿透的近红外光源将携带药物的纳米游泳者递送到皮肤下的生物细胞。观察到的超快纳米游泳者运动从未被报道过，并且不能用斯托克斯定律解释。这个EAGER项目将研究一个假设，即当纳米颗粒被表面等离子体共振（SPR）峰处的光激发时，纳米尺度的气泡围绕颗粒形成（即，超空化）。 这提供了一个几乎无摩擦的环境，允许它以高速移动，前提是气泡可以保持完整。 该项目的目的是通过使用多尺度建模和实验技术分析纳米颗粒在超空化气泡内移动时所经历的力（光学力和流体力）来测试这一假设。该项目包括两项任务。 首先，将进行多尺度建模以了解超空泡中的纳米颗粒动力学。 其次，将进行实验来观察纳米游泳者的动力学和验证计算结果。该项目将揭示涉及纳米光子光学力，光热超空化和纳米级热流体耦合效应的基础物理学。 这项工作的一个重要方面是将研究与教育和培训多学科领域的下一代科学家和工程师相结合，这对技术密集型的美国产业至关重要。我们将教育圣母大学的研究生和科罗拉多梅萨大学（CM）的本科研究人员，这是一所私立本科院校，为近10，000名学生提供服务，其中包括许多农村，第一代，非传统（单亲，退伍军人和归国学生），西班牙裔，和其他学生团体在STEM学科中代表性不足。该奖项反映了NSF的法定使命，并被认为值得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。

Nanoparticles that can be propelled through liquids at high speed (called "nanoswimmers") can play important roles in applications such as targeted-drug delivery, in-situ diagnostics and nanofabrication. For such applications, controlling the direction of high-speed nanoswimmers is critical. However, high-speed nanoswimmers are mostly propelled by forces with random directions, and guided nanoswimmers are currently limited to slow speeds. Designing fully controllable yet fast-moving nanoswimmers thus has significant technological potential. Recent experiments have observed that extremely fast ( 100,000 micron/s) gold nanoparticle swimmers can be directed by light as an external energy source. However, the underlying mechanism is yet to be fully understood. This EAGER project will take the first step toward understanding this phenomenon by studying the force and energy balance of a nanoparticle driven by light. A combination of experiments and numerical simulations of the motion of the nanoswimmers will provide a basic understanding the dynamics of nanoswimmers and resolve questions about the underlying mechanisms of their motion. This, in turn, will provide new information that can lead to a wide range of advanced nanoengineering applications, such as selectively printing nanostructures at a surface for sensing applications or delivering drug-carrying nanoswimmers to biological cells under the skin using skin-penetrable near infrared light sources.The observed ultra-fast nanoswimmer motion has never been reported and could not be explained by Stokes law. This EAGER project will investigate a hypothesis that when the nanoparticle is excited by the light at the surface plasmon resonance (SPR) peak, a nanoscale bubble forms surrounding the particle (i.e., super-cavitation). This provides a near frictionless environment that allows it move at high speed, provided the bubble can remain intact. The objective of the project is to test this hypothesis by analyzing the forces (optical force and fluidic force) the nanoparticle experiences when moving inside the supercavitation bubble using multiscale modeling and experimental techniques. This project consists of two tasks. First, multi-scale modeling will be conducted to understand the nanoparticle dynamics in supercavitation. Second, experiments will be conducted to observe the nanoswimmer dynamics and validate the computation results. This project will unravel fundamental physics involving coupled effects of nanophotonic optical forces, optothermal super-cavitation, and nanoscale thermo-fluids. An essential aspect of this work will be the integration of research with education and training of the next generation of scientists and engineers in multi-disciplinary fields, which are crucial for the technology-intensive U.S. industries. We will educate graduate students at Notre Dame and undergraduate researchers at the Colorado Mesa University (CM), a Primarily Undergraduate Institution serving nearly 10,000 students including many rural, first-generation, non-traditional (single parents, veterans and returning students), Hispanic, and other student groups underrepresented in STEM disciplines.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.