Experimental setup to measure the mechanical properties of colloidal monolayers

胶体单层，即微观粒子的二维组装，是模拟复杂原子结构（包括多晶相和玻璃相）机械性能的迷人试验台。与原子相比，微粒具有易于观察和可变形的突出优点。我们在此请求资助一种定制的仪器来测量胶体单层的机械性能，并将它们与单个粒子的运动联系起来。在平坦的液-液界面上制备了单分子膜，以利用高吸附能并确保运动被限制在二维空间。我们将研究对超过12个数量级的新型机械变形和剪切速率的响应。该项目的第一个关键目标(1)是深入了解微粒之间动量转移相关的胶体目标的物理影响。到目前为止，动量不能通过微粒之间的弹性碰撞传递，因为在胶体系统中惯性的作用可以忽略不计。本文采用激光烧蚀技术使胶体以前所未有的速度运动，并研究了冲击在致密微观组织中的传播。第二个关键目标（O2）是在单颗粒水平上研究流变流动下胶体单层的结构演变。经典流变学在三维空间中工作，因此很少给出单粒子动力学的见解。我们将重点关注由布朗粒子和活性粒子组成的界面，以揭示合成活性物质的流变响应。为了触发上述变形并同时成像单个微粒的运动，提议的仪器将包括以下内置组件：朗缪尔压缩系统，界面磁搅拌器，高速摄像机，脉冲激光源和空间光调制器。此外，我们要求一个物理气相沉积系统来制备感兴趣的胶体颗粒。该仪器还将用于内部协作，旨在了解软硬胶体二元混合物的力学响应和胶体玻璃的受激沉降。

Colloidal monolayers, i.e. two-dimensional assemblies of microscopic particles, are a fascinating testbed to mimic the mechanical properties of complex atomic structures including polycrystalline and glassy phases. In contrast to atoms, microparticles offer the outstanding benefit of being easily observable and deformable. We hereby request funding for a customised instrument to measure the mechanical properties of colloidal monolayers and link them to the motion of the individual particles. Monolayers are prepared at flat liquid-liquid interfaces to harness the high adsorption energies and ensure that the motion is confined in two dimensions. We will study the response to novel mechanical deformations and shear rates spanning more than twelve orders of magnitude. The first key objective of the project (O1) is to gain insight into the physics of impacts in colloidal targets where momentum transfer between microparticles is relevant. To date, momenta cannot be transferred via elastic collisions between microparticles due to the negligible role of inertia in colloidal systems. Here, we use laser ablation to set colloids into motion at unprecedented velocities and study the impact propagation in the dense microstructures. The second key objective (O2) is to investigate, at the single-particle level, the structural evolution of colloidal monolayers under rheometric flows. Classical rheology works in three dimensions and therefore rarely gives insights on the single-particle dynamics. We will focus our attention on interfaces made of Brownian and active particles to unveil the rheological response of synthetic active matter. In order to trigger the above-mentioned deformations and simultaneously image the motion of the individual microparticles, the proposed instrument will include the following built-in components: a Langmuir compression system, an interfacial magnetic agitator, a high-speed camera, pulsed-laser source and a spatial light modulator. Furthermore, we request a a physical vapour deposition system to prepare the colloidal particles of interest. The instrument will be also employed for internal collaboration aimed at understanding the mechanical response of binary mixtures of soft and hard colloids and stimulated sedimentation of colloidal glasses.