Acquisition of a Rheometer Enhanced with Scattering and Imaging for Complex Fluids Research and Education

材料研究仪器计划的这一奖项使哈佛大学能够获得一种具有散射和成像功能的流变仪，用于复杂流体的研究和教育。所有复杂流体的关键特征之一是它们对应力或应变的响应;与所有“软”材料一样，代表复杂流体的较大尺度结构使它们更容易变形，从而有助于定义其最基本的性质。不幸的是，对于许多重要的复杂材料，微观特性与宏观响应的关系仍然知之甚少。这里特别感兴趣的是泡沫和乳液，胶体悬浮液，薄聚合物膜，和电流变悬浮液的机械响应。例如，关于泡沫和乳液，我们将探讨所使用的表面活性剂的界面流变学的整体性质的影响，相关的界面弹性，和流体从间隙空间的排水。此外，哈佛大学的研究人员将研究“堵塞”状态，这些状态会显著影响弱吸引力胶体悬浮液的性质。为了检查这些系统，他们将围绕应力控制流变仪开发仪器，该流变仪将配备两种不同的光学探头：动态光散射和高速数码相机。这项跨学科的合作研究涉及工程、物理和材料科学领域的科学家。该奖项来自材料研究仪器项目，使哈佛大学能够获得一台具有散射和成像功能的流变仪，用于复杂流体的研究和教育。我们都熟悉固体、液体和气体。然而，许多其他普通材料的性质介于简单液体或简单固体的性质之间。例如，考虑诸如用于剃须或洗碗的泡沫。这些材料在受到小应力时会发生有限的应变（很容易自己做这个实验），这是固体的特征，但泡沫的成分（主要是水和空气）都是流体！当然，这种响应受到存在于气体和液体之间的界面处的表面活性剂（基本上是大的高分子）的极大影响。材料的宏观性质主要取决于其不同的组分，通常被称为复杂流体，包括泡沫和乳液，电流变悬浮液（对电场有响应的材料）、聚合物溶液、聚合物膜等。由于宏观响应如此依赖于微观成分，建议的研究将利用现代光学和力学测量进一步研究复杂流体的世界，并将更清楚地阐明微观和宏观特性耦合的方式。

This award from the Instrumentation for Materials Research program allows Harvard University to acquire a rheometer enhanced with scattering and imaging for complex fluids research and education. One of the key features of all complex fluids is their response to stresses or strains; as with all "soft" materials, the larger scale structures that typify complex fluids make them more easily deformed and thus help define their most fundamental properties. Unfortunately, the relationship of microscopic properties to macroscopic response is still poorly understood for many important complex materials. Of particular interest here are the mechanical responses of foams and emulsions, colloidal suspensions, thin polymer films, and electrorheological suspensions. For example, concerning foams and emulsions, we will explore the influence on the bulk properties of the interfacial rheology of the surfactants used, the related interfacial elasticity, and the drainage of fluid from the interstitial space. In addition, researchers at Harvard University will investigate "jammed" states that dramatically influence the properties of weakly attractive colloidal suspensions. In order to examine these systems, they will develop instrumentation around a stress-controlled rheometer, which will be outfitted with two different optical probes: dynamic light scattering and a high-speed digital camera. This collaborative interdisciplinary research involves scientists from engineering, physics, and materials science.This award from the Instrumentation for Materials Research program allows Harvard University to acquire a rheometer enhanced with scattering and imaging for complex fluids research and education. We are all familiar with solids, liquids, and gases. However, many other common materials have properties that are intermediate to those of simple liquids or simple solids. For example, consider a foam such as used for shaving or washing dishes. These materials undergo a finite strain when exposed to a small stress (it is easy to do this experiment for yourself), which is characteristic of a solid, but the constituents of the foam (mostly water and air) are both fluids! Of course, this response is influenced greatly by the surfactants (basically large macromolecules) that reside at the interface between the gas and liquid. Materials whose macroscopic properties depend crucially on the different constituents are commonly referred to as complex fluids, which includes foams and emulsions, electrorheological suspensions (materials that respond to electric fields), polymer solutions, polymer films, etc. Because the macroscopic response is so dependent on the microscopic constituents, the proposed research will use modern optical and mechanical measurements to investigate further the world of complex fluids, and will elucidate more clearly the manner in which the microscopic and macroscopic properties are coupled.