UNS: Imaging inhomogeneous stress networks in colloidal glasses and gels to determine their role in the bulk response of disordered suspensions

CBET-1509308科恩、伊泰通过各种工艺设计的一块玻璃可以安全破碎、防弹、或柔韧。通过操纵组成玻璃的分子之间的微观作用力，可以改变玻璃的性质。研究如何更好地控制这些微观力的分布以及它们在各种加载条件下如何演变是一项重要的技术挑战。这个项目的目的是可视化和确定力，并为玻璃构建模型。通过这些研究获得的理解将产生非常广泛的影响，有可能改变工业制造做法。研究生和本科生都将参与研究和推广，会议项目将使纽约州北部地区的学生和博士后研究人员和行业受益。无序致密胶体悬浮液的变形由材料内部非均匀应力网络的非线性行为控制，该网络对施加的应力做出响应。确定这些局部应力网络的演化如何控制整体流变行为仍然是一个突出的科学挑战。发展这种理解的一个关键障碍是缺乏通过实验测量悬浮液中的局部应力的方法。在这个项目中，一种新的方法--局部结构各向异性应力评估(SALSA)--将具有开创性的能力，能够确定与向下延伸到单个颗粒尺度的样品体积相关的应力。结合最新开发的共焦流变仪设备，正在进行包括压痕、压缩、剪切和双向剪切在内的开创性实验，以量化非均匀应力网络如何相互勾结来控制致密无序胶体悬浮液的整体力学行为。SASA的应用也被扩展到由耗尽相互作用引起的更复杂的粒子间势能。这种扩展的能力被用来研究当裂缝通过的凝胶接近渗流阈值时，裂缝的扩展是如何改变的。除了是优秀的模型体系外，胶体本身也是一项重要的技术。特别是，控制胶体悬浮液的堵塞对于从牙膏到油漆的各种产品的加工都很重要。因此，通过该项目取得的发现将产生非常广泛的影响，有可能改变科学界和工业界的做法。

CBET - 1509308 Cohen, Itai Through various processes a piece of glass can be designed to safely shatter, be bullet proof, or flexible and tough. The glass properties can be changed by manipulating the microscopic forces between the molecules that make up the glass. Learning how to better control the distribution of these microscopic forces and how they evolve under various loading conditions is an important technological challenge. This projects aims to visualize and determine the forces and construct models for the glass. The understanding gained through these studies will have very broad impact with the potential to change industrial manufacturing practices. Both graduate and undergraduate students will be involved in the research and outreach and conference programs will benefit student and postdoctoral researchers and industries in the up-state New York area.The deformation of disordered dense colloidal suspensions is governed by the nonlinear behavior of inhomogeneous stress networks that develop within the material in response to applied stresses. Determining how evolution of these local stress networks governs bulk rheological behaviors remains an outstanding scientific challenge. A key hurdle for developing this understanding is the lack of methods for experimentally measuring the local stresses within suspensions. In this project, a novel method - Stress Assessment from Local Structural Anisotropy (SALSA)- will enable groundbreaking capabilities for determining stresses associated with sample volumes that extend down to the single particle scale. In combination with a newly developed confocal rheometer device, pioneering experiments including, indentation, compression, shear, and biaxial shear are being conducted to quantifying how inhomogeneous stress networks collude to govern the bulk mechanical behavior of dense disordered colloidal suspensions. The application of SALSA is also being extended to more complicated interparticle potentials arising from depletion interactions. This extended capability is being used to study how crack propagation is altered as the gel that it is traveling through approaches a percolation threshold. In addition to being excellent model systems, colloids are an important technology in and of themselves. In particular, controlling the jamming of colloidal suspensions is important for processing products ranging from toothpastes to paints. As such, the findings made through this project will have very broad impact with the potential to change practices in both the scientific and industrial communities.