Programmable Matter: Control Over Material Behaviour Through Scalable Self Assembly

今天创造的物体主要是被动的，也就是说，它们在制造后无法改变其形式或功能。一种超越这一严重限制的新方法是制造嵌入了功能伪像的3D对象，这些功能伪像可以响应外部刺激而改变属性。磁性纳米颗粒之间的静磁相互作用将被用来以比现有的自组装方法更简单和更灵活的方式来制造可逆的自组装结构。从相同的初始磁性纳米颗粒分散开始，外部施加的磁场的变化将提供广泛的几何形状，这些几何形状将在复合材料周围的液体预聚体固化后被捕获。不同的自组装微结构几何结构及其长程组织将使设计和制备这些磁性纳米复合材料中的可调体性质成为可能，例如它们的弹性模数、磁化率和剩磁以及电导和热导率。这些特性将与特定的微结构组件相关，即与过程控制变量相关。这种变革性的方法将使材料的设计和制造具有预先规定的所需特性集。理论、实验和数值模拟都将为这项研究提供信息。这项研究将建立控制变量与自组装结构几何特征之间的比例定律，并通过实验进行验证。光学显微镜将用于二维微尺度成像，X射线计算机层析成像用于三维微尺度成像，而透射电子显微镜将用于纳米尺度成像。数值模拟将使用提供单个粒子的拉格朗日跟踪的布朗动力学，以及使用Landau-Lifshitz-Gilbert方程的磁化动力学，以将研究扩展到实验极限之外。微结构对力学性能的影响，如弹性模量，将用力体积模式下的原子力显微镜和纳米压痕来测量，以记录微观尺度的异质性，并通过拉伸试验来确定其对整体弹性模量和各向异性的影响。剩磁的预测将得到磁力显微镜和自旋极化电子显微镜的验证。块体磁性将使用振动样品磁测法来确定。这项研究将使微结构几何设计能够产生特定的块体材料特性。它有望实现跨越多个学科的变革性应用，例如医学(组织工程和细胞内致动器的脚手架方法)、器件制造(MEMS和自旋电子器件)以及具有可调粗糙度的智能表面(用于芯片实验室设备和基于液滴的微流体)。我们将邀请四名HQP，即两名博士生，一名本科生和一名博士后研究员，通过数学建模、实验和数值模拟，进行跨越磁学、力学、软材料、纳米科学和输运现象的跨学科研究。

Objects created today are primarily passive, i.e., they are unable to change their form or function after fabrication. One new approach to move beyond this severe limitation is to fabricate 3D objects embedded with functional artifacts that can change properties in response to external stimuli. Magnetostatic interactions among magnetic nanoparticles will be used to produce reversible self-assembled structures in a simpler and more flexible manner than available self-assembly methods. Starting from the same initial magnetic nanoparticle dispersion, variations in an externally applied magnetic field will provide a wide range of geometries that will be captured within composite materials after their surrounding liquid prepolymers are solidified. The different self-assembled microstructure geometries and their long-range organization will enable the design and fabrication of tunable bulk properties in these magnetic nanocomposites, such as their elastic moduli, magnetic susceptibility and remanance, and electrical and thermal conductivities. These properties will be correlated with specific microstructure assemblies, i.e., with the process control variables. This transformative approach will enable the design and fabrication of materials with a desired set of properties stipulated a priori. Theory, experiments and numerical simulations will all inform this investigation. This research will develop scaling laws correlating control variables to geometric features of self-assembled structures and validate them through experiments. Optical microscopy will be used for two-dimensional microscale imaging, X-Ray computed tomography for three-dimensional microscale imaging and transmission electron microscopy for nanoscale imaging. Numerical simulations will use Brownian dynamics providing Lagrangian tracking of individual particles coupled with magnetization dynamics using the Landau-Lifshitz-Gilbert equations to extend the investigation beyond experimental limits. The influence of microstructure on mechanical properties such as elastic moduli will be measured using atomic force microscopy in force volume mode and nanoindentation to record microscale heterogeneities, and tensile tests for determining its influence on bulk elastic moduli and anisotropy. Predictions of remanance will be validated by magnetic force microscopy and spin-polarized electron microscopy. Bulk magnetic properties will be determined using vibrating sample magnetometry. This research will enable design of the microstructure geometry to produce specific bulk material properties. It promises transformational applications spanning multiple disciplines, e.g., medicine (scaffolding methods in tissue engineering and intracellular actuators), device fabrication (MEMS and spintronics devices), and smart surfaces with tunable asperities (for lab-on-chip-devices and droplet-based microfluidics). We will involve four HQP, i.e., two Ph.D. students, an undergraduate student and a postdoctoral researcher, to perform interdisciplinary research spanning magnetics, mechanics, soft materials, nanoscience, and transport phenomena using mathematical modeling, experiments and numerical simulations.