Long, Coiled, Actuated: Complex Flagella Moving Through Heterogeneous Fluid Environments

长的、卷曲的、驱动的：复杂的鞭毛在异质流体环境中移动

• 批准号: 1951707
• 负责人: Lisa Fauci
• 金额: $ 36万
• 依托单位: Tulane University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2024-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1951707&HistoricalAwards=false
• 关键词: Long; Coiled; Actuated; Complex; Flagella

The study of how natural and robotic microorganisms propel themselves in a fluid through the beating of flagella has enjoyed much success through advances in imaging technologies, computational methods, microfluidic devices, and materials science. However, in biological systems, rarely does an undulating flagellum beat freely, but may beat in close proximity to (or through) passive elastic structures such as mucosal strands embedded in the fluid environment or walls of tubular ducts. This project will investigate the motility of microorganisms through fluids with suspended polymeric networks where the gaps between polymer filaments are comparable to the size of the organism. The study is relevant to mammalian sperm-egg penetration and spirochete motility through mucosal tissues. The project will also investigate the journey of insect sperm through narrow sperm storage organs in the female reproductive tract. These systems require the development of novel mathematical models and computational methods that move beyond simple representations of sperm flagella, that allow remodeling of discrete viscoelastic networks, and that capture the geometry of confining structures. The project includes training of a postdoctoral researcher, graduate students, and undergraduates through involvement in the research. The mechanics of a compliant, viscoelastic network embedded in a viscous fluid and the motility of long, actuated fibers moving in confined environments present rich systems in elastohydrodyamics. The project will leverage the method of regularized Stokeslets and recent extensions of it. This methodology will be further advanced through deriving kernels for regularized flow inside a sphere. By choosing a discrete network rather than a continuum description of a non-Newtonian fluid, a heterogeneous environment is easily represented. For instance, the power required for an organism to first penetrate the viscoelastic network (as in mammalian fertilization) and how its form evolves as it moves through these regions can be studied. In particular, the energetics of the Lyme disease spirochete as it migrates through such a viscoelastic network will be investigated. In addition, the dynamics of insect sperm motility in the female reproductive tract will be modeled. Their extreme length and their ability to move into confined spaces present mathematical and computational challenges. The project will use recent advances in modeling the shape deformations and buckling of long, flexible fibers in background flows, coupled with modeling of actuated flagella, to investigate this system.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.

通过成像技术、计算方法、微流体装置和材料科学的进步，对自然和机器人微生物如何通过鞭毛的跳动在流体中推动自身的研究取得了巨大成功。然而，在生物系统中，波状鞭毛很少自由跳动，但可能在非常接近（或穿过）被动弹性结构（例如嵌入流体环境中的粘膜线或管状导管壁）时跳动。该项目将研究微生物通过具有悬浮聚合物网络的流体的运动性，其中聚合物丝之间的间隙与生物体的大小相当。该研究与哺乳动物精卵穿透和螺旋体通过粘膜组织的运动有关。该项目还将研究昆虫精子通过女性生殖道狭窄的精子储存器官的旅程。这些系统需要开发新颖的数学模型和计算方法，超越精子鞭毛的简单表示，允许重塑离散粘弹性网络，并捕获限制结构的几何形状。该项目包括通过参与研究来培训博士后研究员、研究生和本科生。嵌入粘性流体中的柔顺粘弹性网络的力学以及在有限环境中移动的长驱动纤维的运动性呈现出丰富的弹流动力学系统。该项目将利用正则化 Stokeslets 方法及其最近的扩展。该方法将通过导出球体内规则化流动的内核来进一步推进。通过选择离散网络而不是非牛顿流体的连续描述，可以轻松表示异质环境。例如，可以研究生物体首先穿透粘弹性网络（如哺乳动物受精）所需的能量，以及其形态在穿过这些区域时如何演变。特别是，将研究莱姆病螺旋体在这种粘弹性网络中迁移时的能量学。此外，还将对女性生殖道中昆虫精子活力的动态进行建模。它们的极端长度和进入有限空间的能力提出了数学和计算挑战。该项目将利用背景流中长柔性纤维的形状变形和屈曲建模的最新进展，再加上驱动鞭毛的建模，来研究该系统。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。

项目成果

Performance of a Helical Microswimmer Traversing a Discrete Viscoelastic Network with Dynamic Remodeling

• DOI: 10.3390/fluids7080257
• 发表时间: 2022-07
• 期刊: Fluids
• 影响因子: 1.9
• 作者: Rudi Schuech;R. Cortez;L. Fauci

The Role of the Double-Layer Potential in Regularised Stokeslet Models of Self-Propulsion

双层势在正则化斯托克斯莱特自推进模型中的作用

• DOI: 10.3390/fluids6110411
• 发表时间: 2021
• 期刊: Fluids
• 影响因子: 1.9
• 作者: Smith, David J.;Gallagher, Meurig T.;Schuech, Rudi;Montenegro-Johnson, Thomas D.
• 通讯作者: Montenegro-Johnson, Thomas D.