Geometry, topology and hydrodynamics of soft active matter

活性物质被广泛地定义为具有内部能量来源的相互作用剂的集体行为;这样的例子可以在许多生命系统中找到，从组织中的细胞集合到哺乳动物或鸟类的集合（这有时被称为生命物质）。然而，越来越多的人造合成系统为研究支配活性物质性质和行为的基本原理提供了富有成效的途径。 生命物质是高度复杂的，很难用严格的定量方式描述。然而，通过分析活组织的整体结构，可以获得相当多的洞察力。已经认识到，大量的生物材料可以被分类为液体、胶体、聚合物、泡沫、凝胶、甚至液晶的特定实例。这些物理系统通常被称为软物质，因为它们在受到热应力或机械应力时能够变形;因此创造了“软活性物质”这一表述以包括大量自推进单元或试剂如细胞或细菌的存在，它引入了一个额外的材料中的（和内部）应力源。三个关键要素成为软活性物质力学所有可能描述的基础：（1）活的马达、细胞和生物体的自发运动（即，其活性）;（2）其经历从各向同性状态到排列状态的相变的能力，从而组织成有序状态（即，它的取向特性）和（3）它的特征流动运动，典型的高粘性流体，它显示出当它被驱动出平衡。在非平衡态热力学的语言中，这些系统表现出两种不同类型的转变：一种是从无序（各向同性，类液体状态）到有序（对齐状态），另一种是从静态行为到流动运动。该项目旨在了解如何使用拓扑学，连续介质力学和统计力学的新思想通过应用全局扰动来控制此类系统的局部性质。活性物质在医学科学中有可能的应用：癌症和伤口愈合，也在材料科学中有可能的应用：智能材料。该项目福尔斯EPSRC领域：生物物理学和软物质物理学，数学科学，流体力学。

Active matter has come to be broadly defined as the collective behaviour of interacting agents that have an internal source of energy; as such examples can be found in many living systems from collections of cells in tissues to collections of mammals or birds (this js sometimes called living matter). However increasingly man-made synthetic systems are providing a fruitful avenue to study the underlying principles that govern the properties and behaviour of active matter. Living matter is highly complex and difficult to describe in a rigorous, quantitative manner. A considerable amount of insight, however, can be gained by the analysis of the overall structure of living tissues. It has been recognized that a large number of biological materials can be classified as particular examples of liquids, colloids, polymers, foams, gels, and even liquid crystals. These physical systems are usually referred to as soft matter because of their ability to deform when subject to thermal or mechanical stresses; the expression soft active matter has thus been coined to include the presence of large numbers of self-propelling units or agents like cells or bacteria, which introduce an additional (and internal) source of stress in the material.Three key elements emerge as the basis for all possible descriptions of the mechanics of soft active matter: (1) the spontaneous motility of living motors, cells and organisms (i.e., its activity); (2) its ability to undergo a phase transition from an isotropic state to an aligned one, thus organising in ordered states (i.e., its orientational properties) and (3) its characteristic flowing motion, typical of highly viscous fluids, that it shows whenit's driven out of equilibrium. In the language of non-equilibrium thermodynamics, these systems show two different types of transitions: one from disorder (isotropic, liquid-like states) to order (aligned states), and one from static behaviour to flowing motion. This project aims to understand how to control local properties of such systems by applying global perturbations using new ideas from topology, continuum mechanics and statistical mechanics. Active matter has possible applications in medical science: cancer and wound healing and also in material science: smart materials. This project falls within EPSRC areas: biophysics and soft matter physics, mathematical sciences, fluid mechanics.