Designing Colloidal Open Crystals for Multifunctional Materials

多功能材料在21世纪颠覆性技术的发展中具有巨大的需求，因为它们能够在单一材料中集成不同的功能。然而，这些材料构成了基本的设计挑战。由数百纳米大小的低配位胶体颗粒构建的开放晶体为通过设计整合光子，声子和机械特性提供了一个令人兴奋的平台，从而为多功能材料提供了一个平台。其中一些性质及其相互作用可能是拓扑起源，为探索拓扑物理学提供了丰富的场所。胶体开放晶格可以充当光子晶体和声子晶体，其可以用于光和声音管理3，4，还提供声子-光子相互作用的机制5。这些声子晶体也可以被设计为支持拓扑保护的机械态6，其可以耦合到光波。虽然光刻为基础的制造技术已被用来实现某些胶体开放晶体的日期，这种自上而下的方法是太昂贵和耗时，特别是对于制造3D晶体结构。胶体构建块的自组装提供了一个低成本，可扩展的制造路线，胶体晶体，但这些往往是紧密堆积。该项目建立在Chakrabarti小组近年来取得的显着进展的基础上，建立了三嵌段片状颗粒的多功能自下而上路线，以产生胶体开放晶体7-9，从而解决了长期存在的挑战。我们的计算方法考虑了设计者胶体颗粒的合成可行性10，11。我们使用两阶段自组装方案的多功能性，建立自下而上的路线，以优化设计的胶体开放晶体。该项目的目的是建立胶体开放晶体，作为集成光学，声学和机械性能的轻质多功能材料的平台。为此，目标如下：1。优化设计胶体开放晶体，用于同时管理光和声; 2.探讨胶体开放晶体的拓扑物理与其光子学、声子学和力学性质的关系; 3.通过开发设计师三嵌段片状颗粒的自组装途径，建立自下而上的制造路线，以优化设计的晶体结构。该研究计划采用了各种计算技术，在Chakrabarti集团（GlOSP和PaSSion）开发的软件包以及开源和/或商业软件中实施。我们使用全局优化来预测片状颗粒的晶体结构，特别是通过三聚体，四面体或八面体形成的颗粒。胶体开放晶体中的空隙允许由互穿晶格产生的显着结构多样性，这可以用于定制和优化性能。我们计算各种晶体结构的光子和声子能带结构，并使用COMSOL和其他开源软件进行多物理分析，以探索拓扑物理。我们使用先进的Monte Carlo方法，包括在PaSSion中实现的自由能计算，以建立自组装途径，从而产生最佳设计的目标晶体。J. Bauer等人，高级材料29，1701850（2017）2. M. Fruchart等人115，E3655（2018）

Multifunctional materials are in great demand for the development of 21st-century disruptive technologies for their ability to integrate different functionalities within a single material. However, these materials pose a fundamental design challenge. Open crystals, built from low-coordinated colloidal particles in the size range of hundreds of nanometres, provide an exciting platform for integrating photonic, phononic and mechanical properties by design, and thus for multifunctional materials 1. Some of these properties and their interplay can be of topological origin, providing a rich playground for exploring topological physics 2. Colloidal open lattices can act as both photonic and phononic crystals, which can be exploited for light and sound management 3,4, also providing mechanisms for phonon-photon interactions 5. These phononic crystals can also be designed to support topologically protected mechanical states 6, which can be coupled to light waves. While lithography-based fabrication techniques have been used to realise certain colloidal open crystals to date, such top-down approaches are too expensive and time-consuming, especially for fabricating 3D crystal structures.Self-assembly of colloidal building blocks offers a low-cost, scalable fabrication route to colloidal crystals, but these tend to be close-packed. This project builds on the remarkable progress achieved in recent years by the Chakrabarti group in establishing versatile bottom-up routes for triblock patchy particles to yield colloidal open crystals 7-9, thereby addressing a long-standing challenge. Our computational approach takes into consideration synthetic feasibility of designer colloidal particles 10,11. We use the versatility of two-stage self-assembly schemes to establish bottom-up routes towards optimally designed colloidal open crystals. The aim of the project is to establish colloidal open crystals as a platform for light-weight multifunctional materials integrating optical, acoustic and mechanical properties. To this end, the objectives are as follows:1. to optimally design colloidal open crystals for simultaneous management of light and sound; 2. to explore topological physics of colloidal open crystals in connection with their photonic, phononic and mechanical properties; 3. to establish bottom-up fabrication routes to optimally designed crystal structures, by exploiting self-assembly pathways for designer triblock patchy particles. The research programme employs a variety of computational techniques, implemented in software packages developed by the Chakrabarti group (GlOSP and PaSSion) as well as in open source and/or commercially available software. We use global optimisation to predict crystal structures for patchy particles, especially formed via trimers, tetrahedra or octahedra. The voids in colloidal open crystals allow for a remarkable structural diversity arising from interpenetrating lattices, which can be exploited to tailor and optimise properties. We compute photonic and phononic band structures for various crystal structures and perform multi-physics analysis using COMSOL and other open-source software as appropriate to explore topological physics. We use advanced Monte Carlo methods including free energy calculations as implemented in PaSSion to establish self-assembly pathways to yield optimally designed target crystals.1. J. Bauer et al., Adv. Mater. 29, 1701850 (2017)2. M. Fruchart et al. 115, E3655 (2018)