NSF-DFG Confine: Chemically-induced phoretic flow, or how to turn a curtain of light into virtual micro-fluidic boundaries

NSF-DFG Confine：化学诱导泳流，或如何将光幕转变为虚拟微流体边界

• 批准号: 2223481
• 负责人: John Brady
• 金额: $ 40万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-10-01 至 2025-09-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2223481&HistoricalAwards=false
• 关键词: NSF; DFG; Confine; Chemically; induced

This award is a collaboration between an experimental group at the University of Potsdam in Germany and a theoretical group at the California Institute of Technology to study the light-activated chemically induced flow of small particles in confined geometries. By applying simple optical stimuli, colloidal particles, both individually and in bulk, can be manipulated with unprecedented levels of control and precision. The research aims to establish the foundation for ‘virtual’ microfluidic devices that utilize soft boundaries generated from light-activated flow patterns whose strength and location are tunable and allow the manipulation and control of colloidal-scale objects. The research has potential technological applications in, for example, cell sorting, DNA manipulation, and the assembly of colloidal-based materials. The collaborative nature of the award will help broaden the horizon of research students as they work with others from different countries and backgrounds, which is increasingly important in this globally connected but fragile world.This award builds on and extends the recently discovered phenomenon of light-driven diffusion-osmosis in which a chemical surfactant’s hydrophobicity is altered by illumination and generates an osmotic pressure gradient that drives fluid and particle motion. The study is aimed at a fundamental understanding of the diffusiophoretic flow; that is, how the motion depends on the basic physical properties of chemical concentration, ionic strength, light intensity, etc., as well as the hydrodynamic interactions among particles and with the confining substrate. Three different processes to manipulate ensembles of particles adjacent to a boundary are investigated: (i) global spatial patterns of light intensity that cause particles to accumulate in (vacate from) regions of low (high) solute concentration, allowing one to ‘paint’ with colloids; (ii) self-generated repulsion between porous (source) particles that crystalize and enhance motion of trapped passive colloids; and (iii) self-propelled Janus particles whose speed and duration can be dynamically controlled. Theory suggests that the light-induced flow profiles, despite being non-equilibrium phenomena, can be expressed in terms of an equilibrium-like chemical ‘solute potential,’ which suggests intriguing analogies to crystallization, phase separation, etc. The award is a close alignment of theory and experiment regarding a unique non-equilibrium system that touches upon many cutting-edge problems of phoretically-driven particle dynamics and hydrodynamics, such as segregation dynamics in mixtures of particles and the motion of active self-propelled particles in dynamically fluctuating confined geometries.This project was awarded through the “Chemistry and Transport in Confined Spaces (NSF-DFG Confine)" opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG).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.

该奖项是德国波茨坦大学的一个实验小组和加州理工学院的一个理论小组之间的合作，通过应用简单的光学刺激、胶体粒子来研究受限几何形状中的光激活化学诱导的小粒子流动。无论是单独的还是批量的，都可以以前所未有的控制和精度水平进行操纵，该研究旨在为“虚拟”微流体装置奠定基础，该装置利用光激活流模式产生的软边界，其强度和位置是可调的。该研究在细胞分选、DNA 操作和胶体材料组装等方面具有潜在的技术应用。该奖项的合作性质将有助于拓宽研究视野。学生与来自不同国家和背景的其他人一起工作，这在这个全球互联但脆弱的世界中变得越来越重要。该奖项建立在最近发现的光驱动扩散渗透现象的基础上并扩展了这一现象，其中化学表面活性剂的疏水性是由光驱动的扩散渗透现象决定的。照明并产生驱动流体和颗粒运动的渗透压梯度；该研究旨在从根本上了解扩散电泳流，即运动如何取决于化学浓度、离子强度、光强度等基本物理特性。 ……以及粒子之间以及与限制基底之间的流体动力学相互作用，研究了操纵边界附近粒子集合的三种不同过程：（i）导致粒子聚集（离开）的光强度的全局空间模式。的地区低（高）溶质浓度，允许用胶体“绘画”；（ii）多孔（源）颗粒之间自生的排斥力，其结晶并增强被捕获的被动胶体的运动；以及（iii）自推进的 Janus 颗粒，其速度理论表明，尽管光诱导的流动剖面是非平衡现象，但可以用类似平衡的化学“溶质电位”来表达，这表明了有趣的类比。该奖项是关于独特的非平衡系统的理论和实验的紧密结合，该系统涉及泳动驱动的粒子动力学和流体动力学的许多前沿问题，例如粒子和流体混合物中的偏析动力学主动自驱动粒子在动态波动的受限几何形状中的运动。该项目是通过“密闭空间中的化学与运输（NSF-DFG Confine）”机会获得的，这是一项合作招标，该奖项涉及美国国家科学基金会和德国研究协会 (DFG)。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。