ERI: Tailoring Piezoresistive Effect of Nanocomposites using Topological Design

该奖项的全部或部分资金来自《2021年美国救援计划法案》(Public Law 117-2)。聚合物纳米复合材料作为多功能电子元件具有巨大的潜力，可以为推进各种应用提供巨大的新机会，如结构健康监测(SHM)、医疗保健、机器人以及国家安全和经济。在纳米复合材料的独特性质中，应变敏感(即压阻效应)是普遍存在的现象。纳米复合材料的高压阻效应可以显著地应用于结构健康监测、可穿戴传感器和机器人等领域的应变传感。另一方面，压阻效应也可能是不受欢迎的，并阻碍纳米复合材料作为柔性显示器、能量采集和多模式传感器的电子元件的应用。因此，需要有效地设计纳米复合材料的压阻效应，并根据目标功能将其调节到最佳范围。目前的设计方法主要集中在设计纳米复合材料的材料组分，由于所得到的材料系统的复杂的过程-结构-性能关系，这通常需要经验的和低效的过程。为了应对这一挑战，本研究旨在建立一种基于拓扑设计的创新设计策略，以可预测的方式设计纳米复合材料的压阻行为。这个项目将提供实践研究机会，让未被充分代表的第一代大学生参与开发基于纳米材料的电子产品。此外，还将在该研究项目的基础上开发一门新的课程和几个多学科的顶石设计项目，这将丰富和改进少数民族服务院校的工程教育。本项目将通过三个研究方向来研究纳米复合材料的压阻效应与拓扑设计之间的关系。首先，将设计两种主要类型的拓扑，包括应力集中拓扑和应力释放拓扑，以改变材料系统中的应力分布。它们对外部载荷的力学响应将通过有限元分析和载荷试验来表征。其次，基于碳纳米管、石墨烯和银纳米线的压阻纳米复合材料将使用添加制造技术来制备，并被图案化以形成预先设计的拓扑结构。将进行机电实验来表征和比较图案化纳米复合材料的压阻响应。此外，还将进行统计分析，以研究压阻行为与拓扑设计之间的关系。第三，为了更好地了解图案化纳米复合材料的压阻性能，基于显微图像对纳米复合材料的微观结构进行统计重建，建立了随机材料模型。然后，使用材料模型来模拟不同拓扑结构的机电响应。将模拟结果与实验测量结果进行比较。这项研究将在拓扑设计对纳米复合材料压阻行为的影响方面产生新的基础知识，这将提高基于纳米材料的多功能电子产品的设计效率和性能。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Polymer nanocomposites hold significant potential as multifunctional electronic components, which can provide tremendous novel opportunities for advancing various applications, such as structural health monitoring (SHM), healthcare, robotics, and national security and economy. Among the unique properties of nanocomposites, strain sensitivity (i.e., piezoresistive effect) has been commonly observed. High piezoresistive effect of nanocomposites can remarkably benefit strain sensing in SHM, wearable sensors, and robotics, among others. On the other hand, piezoresistive effect can also be undesirable and hinder the applications of nanocomposites as electronic components for flexible displays, energy harvesting, and multimodal sensors. Therefore, the piezoresistive effect of nanocomposites needs to be effectively designed and tuned to optimal ranges depending on target functionality. Current design approaches mostly focus on engineering the material components of nanocomposites, which generally entail empirical and inefficient processes due to the complex process-structure-property relationships of resulting material systems. To address this challenge, this research aims to establish an innovative design strategy based on topological design to engineer the piezoresistive behavior of nanocomposites in a predictable manner. This project will provide hands-on research opportunities to engage underrepresented and first-generation college students in developing nanomaterial-based electronics. In addition, a new course and several multidisciplinary capstone design projects will be developed based on this research project, which will enrich and improve the engineering education at a minority-serving institution. This project will investigate the correlation between the piezoresistive effect of nanocomposites and topological design by focusing on three research thrusts. First, two main categories of topologies, including stress-concentrating and stress-releasing topologies, will be designed for altering the stress distribution in the material system. Their mechanical responses to external loads will be characterized via finite element analysis and load tests. Second, carbon nanotube-, graphene-, and silver nanowire-based piezoresistive nanocomposites will be fabricated using additive manufacturing techniques and be patterned to form the pre-designed topologies. Electromechanical experiments will be conducted to characterize and compare the piezoresistive response of the patterned nanocomposites. In addition, statistical analysis will be performed to investigate the correlation between the piezoresistive behavior and the topological design. Third, to better understand the piezoresistive performance of patterned nanocomposites, stochastic material models will be developed by statistically reconstructing the microstructures of nanocomposites based on microscopic images. Then, the material models will be used for simulating the electromechanical responses of different topologies. The simulation results will be compared with the experimental measurements. This research will generate new fundamental knowledge on the effects of topological design on the piezoresistive behavior of nanocomposites, which will enhance the design efficiency and performance of nanomaterial-based multifunctional electronics.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.