Experimental study of the conformation and dynamics of active colloidal polymers

活性胶体聚合物构象与动力学的实验研究

• 批准号: 2028652
• 负责人: Xiang Cheng
• 金额: $ 37.2万
• 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: 2020
• 资助国家: 美国
• 起止时间: 2020-11-01 至 2024-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2028652&HistoricalAwards=false
• 关键词: Experimental; study; conformation; dynamics; active

An active fluid is a dispersion of self-driven particles in a liquid medium. This type of fluid is relevant to a broad class of biological and physical systems including suspensions of swimming microorganisms, synthetic colloidal swimmers and vibrated granular rods. Recent theories and simulations have greatly extended the study of simple active fluids made of compact solid particles to elongated flexible objects such as soft chains and filaments. Such research has transformed our understanding of the dynamics of flexible objects in nonequilibrium conditions (for example, biopolymers within living cells) and revealed unexpected collective dynamics of active fluids. Nevertheless, benchmark experiments that can quantitatively verify the wide range of theoretical and numerical predictions are still missing. This research project aims to address this gap and to perform experiments that study the shape and dynamics of active DNA-linked long chains of colloidal particles, the so-called colloidal polymers in analogy of linear polymer molecules. Two specific systems included in these studies are passive colloidal polymers immersed in light-powered bacterial suspensions and active Janus colloidal polymers whose activity arises internally from individual Janus particles via chemical reactions. The ultimate objective is to explore the possibility of using self-driven active colloidal polymers as artificial flagella. The project includes outreach efforts on designing demos for undergraduate fluid classes and for summer short courses attended by industrial practitioners. The project also aims to forge close collaborations between academic and industrial researchers.DNA-linked colloidal chains provide a concrete example of the classic bead-spring model of polymer molecules. By conveying activity to DNA-linked colloidal polymers, the research team will investigate the conformation and dynamics of active colloidal polymers and understand the fundamental polymer scaling relations out of equilibrium. The researchers will verify important theoretical and numerical predictions on the unusual behaviors of active polymers such as the swelling of polymer chains with activity, the self-assembly of hairpin structures, and the activity-induced softening and coil-to-globule transition. Moreover, by exploiting the collective dynamics of linked active Janus particles, the project participants will study a new approach for creating self-driven artificial flagella with periodic non-reciprocal beating motions. Such a flagellar structure would then be tested for driving the locomotion of synthetic microswimmers. Taken together, the project provides not only benchmark experiments corroborating existing theories and simulations but also a new way to engineer synthetic microswimmers for cargo delivery at microscopic scales.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.

活性流体是自驱动颗粒在液体介质中的分散体。这种类型的流体与广泛的生物和物理系统相关，包括游动微生物的悬浮液、合成胶体游动体和振动颗粒棒。最近的理论和模拟已极大地将由致密固体颗粒组成的简单活性流体的研究扩展到细长的柔性物体，例如软链和细丝。此类研究改变了我们对非平衡条件下柔性物体（例如活细胞内的生物聚合物）动力学的理解，并揭示了活性流体意想不到的集体动力学。然而，仍然缺乏能够定量验证各种理论和数值预测的基准实验。该研究项目旨在解决这一差距，并进行实验来研究活性 DNA 连接的胶体颗粒长链的形状和动力学，即所谓的胶体聚合物，类似于线性聚合物分子。这些研究中包括的两个特定系统是浸入光动力细菌悬浮液中的被动胶体聚合物和活性Janus胶体聚合物，其活性通过化学反应从单个Janus颗粒内部产生。最终目标是探索使用自驱动活性胶体聚合物作为人工鞭毛的可能性。该项目包括为本科流体课程和工业从业者参加的夏季短期课程设计演示的推广工作。 该项目还旨在建立学术和工业研究人员之间的密切合作。DNA 连接的胶体链提供了聚合物分子经典珠弹簧模型的具体例子。通过将活性传递给 DNA 连接的胶体聚合物，研究小组将研究活性胶体聚合物的构象和动力学，并了解不平衡状态下聚合物的基本缩放关系。研究人员将验证活性聚合物异常行为的重要理论和数值预测，例如活性聚合物链的膨胀、发夹结构的自组装以及活性诱导的软化和卷曲到球体的转变。此外，通过利用相互关联的活性 Janus 粒子的集体动力学，项目参与者将研究一种新方法，用于创建具有周期性非往复跳动运动的自驱动人工鞭毛。然后将测试这种鞭毛结构是否驱动人造微型游泳器的运动。总而言之，该项目不仅提供了证实现有理论和模拟的基准实验，而且还提供了一种设计用于微观尺度货物运输的合成微型游泳器的新方法。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力评估进行评估，被认为值得支持。优点和更广泛的影响审查标准。

项目成果

Crack patterns of drying dense bacterial suspensions

干燥致密细菌悬浮液的裂纹模式

• DOI: 10.1039/d2sm00012a
• 发表时间: 2022
• 期刊: Soft Matter
• 影响因子: 3.4
• 作者: Ma, Xiaolei;Liu, Zhengyang;Zeng, Wei;Lin, Tianyi;Tian, Xin;Cheng, Xiang
• 通讯作者: Cheng, Xiang

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

To cross or not to cross: Collective swimming of Escherichia coli under two-dimensional confinement

• DOI: 10.1103/physrevresearch.4.023105
• 发表时间: 2022-05-09
• 期刊: PHYSICAL REVIEW RESEARCH
• 影响因子: 4.2
• 作者: Ghosh, Dipanjan;Cheng, Xiang
• 通讯作者: Cheng, Xiang

Density fluctuations and energy spectra of 3D bacterial suspensions

3D 细菌悬浮液的密度波动和能谱

• DOI: 10.1039/d1sm01183a
• 发表时间: 2021
• 期刊: Soft Matter
• 影响因子: 3.4
• 作者: Liu, Zhengyang;Zeng, Wei;Ma, Xiaolei;Cheng, Xiang
• 通讯作者: Cheng, Xiang