Self-Assembly of Shape-Defined Micro-Hydrogels: Top-Down Meets Bottom-Up

自然界使用遗传密码来决定蛋白质的结构，而蛋白质的结构反过来又支撑着它们的功能。然而，在制造合成材料时，没有类似于遗传密码的东西。该项目的目标是通过将具有特定形状的软聚合物微粒(尺寸在1-1000微米范围内的微粒)组装成精确可控的排列来创建一个制造材料的平台。研究思路是，引导聚合物微粒组装所需的分子信息可以嵌入到微粒本身中。粒子将在配备流动光刻的微流控系统中形成，这是一种粒子合成方法，通过将聚合物暴露在紫外光下，在精确控制下制造微粒子。然后，粒子组装成结构的过程将由在微粒表面形成图案的分子引导。一旦建立，该平台可以用于构建各种创新结构，例如可治愈和可回收的组织模拟材料、收集废物能源的自组装微型机器，或者在生物环境中执行复杂任务的软微型机器人。为了扩大对STEM研究的参与，该项目将与校园组织合作，为未被充分代表的高中生和本科生提供几种研究和教育经验。中尺度上的可编程自组装仅限于周期晶格、一维链和小的高度对称的集群。目前还不可能对粒子的自组装进行编程，达到生物学或使用自上而下的方法(如3-D打印)所达到的复杂程度。这种方法的缺乏限制了对各向异性或高度详细结构的自下而上的访问。尽管形状定义微凝胶的制备方法和应用很多，但其分级自组装成有序超结构的研究还很有限。使用定制的流动光刻设备，该项目的研究人员将控制各种功能分子对(例如，电荷配对和主客体基序)如何在序列定义的一维和形状定义的二维聚合物微凝胶中定位。这种合成方法将对控制粒子在哪里以及如何相互作用以及它们如何对刺激做出反应的信息进行编码。这些组件将足够大，可以在显微镜下直接观察，从而促进经验框架的发展，以理解和预测信息-结构-属性-行为关系。这种自上而下和自下而上制造技术的组合将实现一种通用的战略，用于将分子水平的工作扩大到中尺度和更高的尺度，高通量合成软胶体的复杂几何图形，以及用于构建和驱动软微机械的更多样化的模式库和刺激库。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nature uses a genetic code to dictate the structures of proteins which, in turn, underpin their functions. However, there is no analog to a genetic code when fabricating synthetic materials. The goal of this project is to create a platform for fabricating materials by assembling soft, polymeric microparticles (particles whose sizes are in the 1-1000 micrometer range) with specific shapes into precisely controlled arrangements. The research idea is that that the molecular information necessary to guide the assembly of the polymeric microparticles can be embedded into the particles themselves. The particles will be formed in a microfluidic system equipped with flow lithography, which is a particle synthesis method for fabricating microparticles by exposing polymers to UV light under precise control. Then, the assembly of the particles into structures will be guided by molecules that are patterned onto the microparticle surfaces. Once established, the platform could be used to construct a variety of innovative structures, such as healable and recyclable tissue-mimetic materials, self-assembled micromachines that harvest waste energy, or soft micro-robots that execute complex tasks in biological environments. To broaden participation in STEM research, the project will support several research and education experiences for underrepresented high school and undergraduate students in collaboration with campus organizations.Programmable self-assembly on the mesoscale is limited to periodic lattices, one-dimensional chains, and small high-symmetry clusters. It is not yet possible to program the self-assembly of particles at the level of sophistication that is achieved in biology or using certain top-down approaches such as 3-D printing. This dearth of methodology limits bottom-up access to anisotropic or highly detailed structures. Despite the emergence of many preparation methods and applications of shape-defined microgels, research on their hierarchical self-assembly into ordered superstructures is limited. Using custom-built flow lithography devices, researchers on this project will control how various functional molecule pairs (e.g., charge-pairing and host-guest motifs) are localized within sequence-defined, one-dimensional and shape-defined two-dimensional polymer microgels. This synthetic method will encode information that governs where and how the particles interact and how they respond to stimuli. The assemblies will be large enough for direct observation in a microscope, facilitating the development of an empirical framework to understand and predict the information-structure-property-behavior relationships. This combination of top-down and bottom-up fabrication techniques will enable a versatile strategy for scaling up molecular-level work to the mesoscale and beyond, the high-throughput synthesis of complex geometries for soft colloids, and a more diverse library of motifs and stimuli for building and actuating soft micro-machines.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.