Energy Landscape Approaches to Understanding Soft Glassy Materials

该奖项支持计算机模拟和相关教育，旨在帮助理解一类材料的机械性能，这些材料是粘弹性的，既不是完全固体也不是完全液体，包括肥皂泡沫、牙膏、蛋黄酱和活细胞。值得注意的是，这些看似非常不同的材料对被拉或挤压的反应非常相似，而且在很大程度上挑战了深入的理解。该项目建立在最近一项突破的基础上，该突破源于将该系统视为类似于抽象能源景观上的粒子滚落山坡。也就是说，泡沫中单个气泡看似复杂的运动，当投射到这个抽象的空间时，就像河流峡谷的曲折。PI将寻求更好地了解导致河流扭曲和转弯的景观形状，制作新版本的模型，使河流具有不同的形状，并为模型添加真实世界的细节。类似的“景观”方法也被发现在机器学习算法中很有用，有很多应用，这表明我们开发的算法和我们的发现可能会在材料研究领域之外找到有用的应用。该项目将培训研究生和本科生在这一重要的最先进的研究领域。技术摘要该奖项支持理论和模拟研究以及了解软玻璃材料的教育，软玻璃材料是一类广泛的材料，包括泡沫、乳液、浆料甚至活细胞，它们共享一组共同的不寻常的粘弹性特性，其物理起源仍然是非常神秘的。它将建立在使用泡沫模型的最新研究的基础上，该模型表明，软玻璃材料的不寻常力学--幂定律流变学、超扩散粒子运动和雪崩--是由于组态空间中S路径系统的分形特性。具体地说，它将扩展模型以捕捉粘性阻尼和外加剪切的影响，产生具有不同分维的构型路径的模型，以及探索能量景观本身的分形几何。最终结果是开发了一套用于驱动非平衡系统的工具，以探索和理解能量景观的几何及其与材料属性的关系。更广泛地说，许多复杂适应系统的行为，包括我们身体中的细胞，可能取决于嵌入在高维空间中的一些非常复杂的能量或适应环境的最小化，由于计算的进步，这种深入研究现在才变得实用。这个跨学科的项目将为研究生和本科生提供充分的机会，开发最先进的工具来研究这种高维度的能量和健身景观。在这项提案中开发的工具将公开传播，我们预计它们将在材料科学之外找到实用价值。

NONTECHNICAL ABSTRACTThis award supports computer simulation and associated education aimed to help understand the mechanical properties of a class of materials that are viscoelastic, being neither entirely solid nor liquid, and which include soap foams, toothpaste, mayonnaise and living cells. Remarkably, these seemingly very different materials respond very similarly to being pulled or squeezed, and have largely defied deep understanding. This project builds upon a recent breakthrough that stems from thinking of the system as analogous to a particle rolling downhill on an abstract energy landscape. That is, the seemingly complicated motion of the individual bubbles in a foam, when projected into this abstract space, resembles the twists and turns of a river canyon. The PIs will seek to better understand the shape of the landscape that causes the 'river' to twist and turn as it does, to make new versions of the model that give rise to 'rivers' having different shapes and to add real-world detail to the model. Similar 'landscape' approaches have also been found to be useful in machine learning algorithms with many applications, suggesting that the algorithms we develop and our findings may find useful application outside the field of Materials Research. This project will train both graduate and undergraduate students in this important state of the art research area.TECHNICAL ABSTRACT This award supports theoretical and simulation research and education to understand soft glassy materials, a broad class of materials including foams, emulsions, pastes, slurries and even living cells, that share a common set of unusual viscoelastic properties whose physical origins remain deeply mysterious. It will build upon recent studies using a foam model that show that the unusual mechanics of soft glassy materials - power-law rheology, super-diffusive particle motion and avalanches - are due to fractal properties of the system?s path in configuration space. Specifically, it will extend the model to capture the effects of viscous damping and applied shear, produce models having configuration paths with different fractal dimensions as well as probe the fractal geometry of the energy landscape itself. The net result is the development of a suite of tools for the actuation of non-equilibrium systems to probe and understand the geometry of energy landscapes and its relation to material properties. More broadly, it appears that the behavior of many complex adaptive systems, including the cells in our bodies, may be determined by the minimization of some very complex energy or fitness landscape embedded in a high-dimensional space, whose in-depth study is only now becoming practical due to advances in computation. This interdisciplinary project will provide ample opportunity for graduate and undergraduate student training in the development of state of the art tools for studying such high-dimensional energy and fitness landscapes. The tools developed in this proposal will be disseminated openly, and we anticipate them finding utility outside of material science.