An experimental study of rheology and microscopic dynamics of sheared active fluids

剪切活性流体的流变学和微观动力学实验研究

• 批准号: 1702352
• 负责人: Xiang Cheng
• 金额: $ 46.7万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1702352&HistoricalAwards=false
• 关键词: experimental; study; rheology; microscopic; dynamics

CBET - 1702352PI: Cheng, XiangThis award will provide support to develop two new instruments to study the properties of active fluids. An active fluid is a suspension of particles in liquid that can generate their own motion and propel themselves. There are both synthetic and naturally-occurring active suspensions. This proposal will focus on suspensions of bacterial cells, which exhibit fascinating motions based on the coordinated behavior of many cells. The cells' motions cause these fluids to flow in new and unusual ways. An ultra-fast confocal microscope equipped with a chamber that can generate flow will be built at the University of Minnesota. This instrument will allow investigators to observe cellular motion on the scale of individual cells as well as detect coordinated structures that develop among the cells in flow. A thin-film rheometer will be built at Cal Poly - San Luis Obispo. This instrument will measure bulk properties of the active suspensions. The results of these experiments will help validate computational and theoretical studies of active suspensions. The instruments will also be useful for studying other complex fluids where microscopic arrangements of suspended particles influence the fluid dynamics of the suspension. The investigators will involve undergraduates in the research, including students from traditionally underrepresented groups in science and engineering. In addition, they will create new demonstrations of active suspensions to engage the public at the Minnesota State Fair and at Cal Poly's open house and pre-collegiate symposium. This project will reveal direct correlations between microscopic active particle dynamics and macroscopic flow behaviors of active suspensions. Specifically, the most-widely studied active suspension, that of E. coli, will be investigated. Two fundamental questions will be addressed. First, what is the dynamical origin of the superfluid phase of bacterial suspensions with extremely low or even zero apparent viscosity? Second, how does an externally imposed shear flow influence the dynamics of individual active particles in concentrated bacterial suspensions? Thus, the experiments will address two key questions underlying the predictions of theories of active suspensions. The experiments will unambiguously reveal the microscopic origin of unusual rheology of active fluids and provide a solid experimental foundation for the development of the field. Results from this project are expected to help practitioners find better ways to control transport in biological suspensions, prevent formation of biofilms, control viscosity in suspensions, and improve mixing in microfluidic devices used in bioassays and advanced materials synthesis.

CBET - 1702352PI：程翔该奖项将支持开发两种新仪器来研究活性流体的特性。活性流体是液体中颗粒的悬浮液，可以产生自身运动并推动自身。有合成的和天然存在的活性悬浮液。该提案将重点关注细菌细胞的悬浮液，它们根据许多细胞的协调行为表现出令人着迷的运动。细胞的运动导致这些液体以新的和不寻常的方式流动。明尼苏达大学将建造一台配备可产生流动的腔室的超快共焦显微镜。该仪器将使研究人员能够观察单个细胞尺度上的细胞运动，并检测流动中细胞之间形成的协调结构。加州理工大学圣路易斯奥比斯波分校将建造一台薄膜流变仪。该仪器将测量活性悬浮液的整体特性。这些实验的结果将有助于验证主动悬架的计算和理论研究。这些仪器还可用于研究其他复杂流体，其中悬浮颗粒的微观排列会影响悬浮液的流体动力学。研究人员将让本科生参与研究，其中包括来自传统上在科学和工程领域代表性不足的群体的学生。此外，他们还将在明尼苏达州博览会以及加州理工大学的开放日和大学预科研讨会上制作新的主动暂停演示，以吸引公众参与。该项目将揭示微观活性粒子动力学与活性悬浮液的宏观流动行为之间的直接相关性。具体来说，将研究最广泛研究的活性悬浮液，即大肠杆菌的活性悬浮液。将解决两个基本问题。首先，表观粘度极低甚至为零的细菌悬浮液超流相的动力学起源是什么？其次，外部施加的剪切流如何影响浓缩细菌悬浮液中单个活性颗粒的动力学？因此，这些实验将解决主动悬架理论预测背后的两个关键问题。这些实验将明确揭示活性流体异常流变的微观起源，并为该领域的发展提供坚实的实验基础。该项目的结果预计将帮助从业人员找到更好的方法来控制生物悬浮液中的运输，防止生物膜的形成，控制悬浮液中的粘度，并改善生物测定和先进材料合成中使用的微流体装置的混合。

项目成果

The colloidal nature of complex fluids enhances bacterial motility

• DOI: 10.1038/s41586-022-04509-3
• 发表时间: 2022-03-31
• 期刊: NATURE
• 影响因子: 64.8
• 作者: Kamdar, Shashank;Shin, Seunghwan;Cheng, Xiang
• 通讯作者: Cheng, Xiang

Rheology of bacterial suspensions under confinement

• DOI: 10.1007/s00397-019-01155-x
• 发表时间: 2019-08-01
• 期刊: RHEOLOGICA ACTA
• 影响因子: 2.3
• 作者: Liu, Zhengyang;Zhang, Kechun;Cheng, Xiang
• 通讯作者: Cheng, Xiang

Symmetric shear banding and swarming vortices in bacterial superfluids

• DOI: 10.1073/pnas.1722505115
• 发表时间: 2018-07-10
• 期刊: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• 影响因子: 11.1
• 作者: Guo, Shuo;Samanta, Devranjan;Cheng, Xiang
• 通讯作者: Cheng, Xiang

Miniature magnetic rod interfacial stress rheometer for general-purpose microscopes

用于通用显微镜的微型磁棒界面应力流变仪

• DOI: 10.1122/8.0000263
• 发表时间: 2021
• 期刊: Journal of Rheology
• 影响因子: 3.3
• 作者: Qiao, Yiming;Fan, Chen;Liu, Zhengyang;Medina, Dani;Keim, Nathan C.;Cheng, Xiang
• 通讯作者: Cheng, Xiang