Rheometer for the study of structured soft materials

流体和固体的宏观性质是由微观相互作用决定的。在我的研究计划中，我研究自组装胶体系统的结构和动力学。胶体悬浮液是颗粒在流体中的悬浮液，其中颗粒足够小，使得它们不断地被周围流体中的分子推挤。这被称为布朗运动-在1905年爱因斯坦假设，布朗运动的胶体确实是一个证明的分子性质的流体。微观胶体结构修改宏观流动特性的流体。番茄酱是一种具有粘弹性的胶体流体：在没有剪切的情况下更像固体，但在存在剪切的情况下变稀。虽然即使是胶体流体也可以表现出对剪切的复杂响应（“流变行为”），但预期接近无定形固体（“玻璃”）相的特征在于在显微镜观察到的扩散系数和宏观粘性性质之间的经典关系（称为斯托克斯-爱因斯坦关系）的破裂。然而，胶体悬浮液形成许多各向异性的结构，包括在外部电场的存在下的结晶胶体相。这种微观现象与固体状流变响应的增加相结合：固体在极限应力以下不会屈服，这种材料被称为电流变流体。在胶体玻璃化转变和电流变效应的研究中，主要目标是理解微观机制以及微观结构与宏观性能之间的关系。流变仪将使大量的胶体悬浮液的粘弹性研究在存在和不存在外部电场，并将提供微观和宏观性质之间的关键环节。流变仪将有利于研究社区的其他成员作为一个有价值的研究和培训工具。

Macroscopic properties of fluids and solids are determined by microscopic interactions. In my research programme, I study structure and dynamics in self-assembling colloidal systems. Colloidal suspensions are suspensions of particles in a fluid where the particles are small enough that they are constantly kept jostling by the molecules in the surrounding fluid. This is termed Brownian motion - in 1905 Einstein postulated that Brownian motion in colloids was indeed a proof of the molecular nature of the fluid.Microscopic colloidal structure modifies the macroscopic flowing characteristics of the fluid. Tomato ketchup is a colloidal fluid that exhibits viscoelastic properties: more solid-like in the absence of shear but thinning in the presence of shear. While even colloidal fluids can exhibit a complex response to shear ("rheological behaviour"), it is expected that the approach to an amorphous solid ("glass") phase is characterized by a breakdown of a classic relationship, known as the Stokes-Einstein relation, between microscopically observed diffusion coefficients and the macroscopic viscous properties.Colloidal suspensions can exhibit glassy behaviour when crystallization is suppressed. However, colloidal suspensions form many anisotropic structures including crystalline colloidal phases in the presence of external electric fields. This microscopic phenomenon is coupled with an increase in solid-like rheological response: the solid does not yield below a limiting stress, and such a material is termed an electrorheological fluid. In the study of both the colloidal glass transition and the electrorheological effect, the primary goals are the understanding of microscopic mechanisms and the relationship between micro-structure and macroscopic properties. A rheometer will enable the study of viscoelastic properties of bulk colloidal suspensions in the presence and absence of an external electric field, and will provide the crucial link between microscopic and macroscopic properties.The rheometer will benefit other members of the research community as a valuable research and training tool.