Large Scale Continuous Layer-by-Layer Assembly of Paper-based Nanocomposites for High Fidelity Multifunctional Sensors

纸是中国古代发明的一种普遍存在的材料，由纤维素纤维相互缠绕和扭曲形成一个多孔的网络。今天好吗?随着数字化世界的不断发展，人们对纸张产生了新的兴趣，因为它是一种低成本、可持续、灵活、轻便且具有生物相容性的便携式电子产品平台。该项目将为将纳米材料（如碳纳米管（CNTs）和纤维素纳米纤维（CNFs））纳入纤维网络提供框架，其目标是使纸基纳米复合材料（PBC）的规模化生产变得容易。该资助为开发模仿工业造纸的连续逐层组装工艺提供了基础知识，以制造具有导电性、增强强度和对外部刺激高灵敏度的应变传感器，用于多功能传感应用。这种新工艺有可能重振纸浆和造纸工业，使美国经济受益，并通过改变智能材料和电子设备的制造方式，促进科学进步，并将其用于可穿戴设备、医疗保健应用、结构监测系统、软机器人和电子皮肤等应用。跨学科的方法鼓励不同的个人，包括妇女和代表性不足的少数群体参与工程研究和教育。纸基纳米复合材料在连续卷筒纸中的逐层组装可以克服现有多功能传感器的一些限制，包括成本、灵活性、耐用性和机械灵敏度。本基础研究旨在填补以下方面的知识空白：为将高含量分散良好的纳米颗粒整合到增氧纤维网络中而进行界面裁剪；以及通过微裂纹辅助操作来控制纸基纳米复合材料中渗透导电结构的断开-重新连接。补体纸纳米复合材料具有负泊松比，这意味着它们在拉伸过程中双轴膨胀，与传统材料在张力下承受横向泊松压缩形成直接对比。缺氧材料中的双向膨胀有助于使导电纳米颗粒彼此远离，从而提高可拉伸电阻传感器的灵敏度。通过数值模拟研究了机械运动与电子输运之间的耦合关系，并进行了实验研究，验证了模型的正确性，验证了结构泊松比和应变浓度可定制以实现超高机械灵敏度的假设，并建立了纸质多功能传感器的工艺-结构-性能关系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Paper is a ubiquitous material invented in ancient China comprising cellulose fibers tangled and twisted with each other forming a porous network. Today?s ever-digitalized world has spurred new interests in paper as a low-cost, sustainable, flexible, lightweight and biocompatible platform for portable electronics. This project will provide the framework for the incorporation of nanomaterials, such as carbon nanotubes (CNTs) and cellulose nanofibrils (CNFs), into fibrous networks, with the goal of enabling easy scale-up manufacturing of paper-based nanocomposites (PBC). The grant provides fundamental knowledge for the development of a continuous layer-by-layer assembly process, mimicking industrial papermaking, to manufacture strain sensors with electrical conductivity, enhanced strength and high sensitivity to external stimuli for multifunctional sensing applications. This novel process has the potential to reinvigorate the pulp and paper industry and benefit the U.S. economy and promote the progress of science by changing the way smart materials and electronic devices are manufactured and used for applications such as wearable devices, healthcare applications, structural monitoring systems, soft robotics, and electronic skins. The interdisciplinary approach encourages the participation of diverse individuals including women and underrepresented minority groups in engineering research and education. The layer-by-layer assembly of paper-based nanocomposites in a continuous web former can overcome several limitations existing multifunctional sensors have, ranging from cost, flexibility, durability, and mechanosensitivity. This fundamental study is to fill the knowledge gaps on interface tailoring for the incorporation of well-dispersed nanoparticles at high content into auxetic fiber networks, and on microcrack-assisted manipulation to control the disconnection-reconnection of percolated conductive structures in paper-based nanocomposites. Auxetic paper nanocomposites possess a negative Poisson's ratio, meaning they expand biaxially during stretching, in direct contrast to conventional materials, which endure transverse Poisson compression under tension. Bidirectional expansions in auxetic materials contribute to moving electrically conductive nanoparticles away from one another, thereby improving the sensitivity of stretchable resistive sensors. Numerical simulations are performed to understand the coupling between mechanical motion and electron transport in auxetic materials, while experimental research is conducted to verify the model, test the hypothesis that structural Poisson's ratio and strain concentration can be tailored to achieve ultrahigh mechanosensitivity, and establish process-structure-property relationships in paper-based multifunctional sensors.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.