Driven, directed or crowded: dynamics of soft matter near and far from equilibrium

理解非平衡物理学的统一框架并不存在。在这个研究项目中，我们将研究三类实验模型系统的动力学，这些系统是不平衡的，它们解决了非平衡行为的补充方面：能量注入和耗散，粒子间相互作用的修改和环境的作用。 * 第一个目标是创建动态响应材料。首先，我们希望大量制造微米级、单分散、不对称的布朗设计者液滴。为相行为研究制作复杂的胶体结构具有挑战性。我们的假设是，驱动系统远离平衡，在这种情况下，通过电流体动力学液滴分裂，将使我们能够创建更小的结构。其次，活细胞中的自驱动运动（称为活性）本质上是纳米级的;然而，所有活性物质的胶体类似物都是微米级和二维的。我们将设计一个纳米级的光激活马达，使用细菌视紫红质（一种光激活质子泵）嵌入脂质bicelle，并检查，使用非生命模型系统中的实验，活性在生命系统中指导组织的作用。第二个目的是研究胶体团簇形成的动力学。竞争胶体相互作用可导致中间顺序的结构：例如，长程静电排斥和短程耗尽力的组合产生团簇、凝胶和玻璃态。我们将第一次研究耗尽和各向异性偶极力的组合。 有了这个，我们希望解决一个长期存在的问题：偶极气-液转变存在吗？然后，我们将开关偶极相互作用和定量研究集群形成的动力学。与此同时，我们将研究观察到但不理解的特殊聚类现象。我们将测试我们的假设，即这种聚集是电荷调节的结果，这可能会导致均匀胶体系统中自发的电荷不对称性。第三个目标是了解拥挤环境对活细胞中分子动力学和构象的影响：这被称为大分子拥挤。虽然已经出现了一些定性的见解，以其性质，一个真正的定量的理解，甚至在简单的模型系统是无法实现的。使用合成聚合物作为拥挤和探针分子，我们将研究电荷，多分散性和流体动力学相互作用的作用，使用一套不同的实验工具。我们将比较合成聚合物探针分子与真实的蛋白质，以及合成拥挤与真实的细菌细胞材料。**对胶体自组装的控制导致了根本性的进步和新材料的出现。我们的愿景是，将自组装的研究扩展到远离平衡的系统，直觉往往会失败，这将导致新的基本见解。

A unifying framework for understanding non-equilibrium physics does not exist. In this research program we will study dynamics in three classes of experimental model systems that are out of equilibrium which address complementary aspects of non-equilibrium behavior: energy injection and dissipation, modification of interparticle interactions and role of environment. ******The first objective is to create dynamically responsive materials. First, we wish to make micron-scale, monodisperse, asymmetric Brownian designer droplets in large quantities. Making complex colloidal structures for phase behavior studies is challenging. Our hypothesis is that driving systems far from equilibrium, in this case via electrohydrodynamic drop breakup, will enable us to create smaller structures. Second, self-driven motion in living cells (termed as activity) is inherently nanoscale; however, all colloidal analogs of active matter have been micron-scale and 2-dimensional. We will devise a nanoscale light-activated motor, using bacteriorhodopsin (a light-activated proton pump) embedded in a lipid bicelle, and examine, using experiments in a non-living model system, the role of activity in directing organization in living systems.******A second objective is to study kinetics of colloidal cluster formation. Competing colloidal interactions can result in structures of intermediate order: e.g., the combination of long-range electrostatic repulsions and short-range depletion forces gives clusters, gels, and glassy states. We will examine, for the first time, the combination of depletion and anisotropic dipolar forces. With this, we hope to address the long-standing question: does the dipolar gas-liquid transition exist? We will then switch dipolar interactions on and off to study kinetics of cluster formation quantitatively. Parallel to this, we will examine peculiar clustering phenomena that are observed but not understood. We will test our hypothesis that this clustering is a consequence of charge regulation, which can give rise to spontaneous charge asymmetries in a homogeneous colloidal system.******A third objective is to understand the effect of the crowded environment on molecular dynamics and conformations in living cells: this is referred to as macromolecular crowding. While several qualitative insights have emerged as to its nature, a true quantitative understanding is not achieved even in simple model systems. Using synthetic polymers both as crowder and probe molecule, we will examine the role of charge, polydispersity, and hydrodynamic interactions using a diverse set of experimental tools. We will compare synthetic polymer probe molecules with real proteins, as well as synthetic crowders with real bacterial cell material.******Control of colloidal self-assembly has led to fundamental advances and to new materials. The vision is that extending the study of self-assembly to systems far from equilibrium, where intuition often fails, will lead to new fundamental insights.*****