Collaborative Research: Multiscale Mechanics of Adsorption-Deformation Coupling in Soft Nanoporous Materials

合作研究：软纳米多孔材料吸附变形耦合的多尺度力学

• 批准号: 2113558
• 负责人: Wenjie Xia
• 金额: $ 20.67万
• 依托单位: North Dakota State University Fargo
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2113558&HistoricalAwards=false
• 关键词: Collaborative; Research; Multiscale; Mechanics; Adsorption

This grant supports research to pursue a fundamental understanding of adsorption-deformation coupling in soft nanoporous materials. The research will develop corresponding mechanical theories, aiming to better predict hygroscopic movements in complex nanoporous media and control sorption-induced actuation by design where sorption refers to the binding of ions to charged surfaces. Soft nanoporous materials having characteristic pore sizes below 100 nm are ubiquitous in nature (e.g., cellulose, protein) and in engineering applications (e.g., cement, gel, nanocomposites). These materials often exhibit significant swelling/shrinkage upon adsorption/desorption of fluids/gases due to nanoconfinement effects resulting from their network topology and interfacial interactions. Nature uses such stimuli-responsive features of cellulose nanofibers to facilitate the dispersal of plant seeds upon humidity change. Bio-inspired soft nanoporous materials have been recently developed for fast and reliable actuators, sensors, and artificial muscles driven by sorption of solvent molecules. This project will establish and validate a multiscale mechanics framework informed by pore-scale thermodynamics and molecular simulations for predicting the sorption-induced straining of nanoporous materials. The project will also pursue an educational initiative involving new course development on multiscale poromechanics and pre-college outreach by harnessing the excitement surrounding nano-engineered materials and leveraging it with the exceptional infrastructure for innovation and education at the participating institutes. This research is driven by the hypothesis that the complex coupling between sorption and deformation in nanoporous media can be predicted by focusing on two key pore-scale attributions, namely the disjoining pressure and surface tension induced by solid-adsorbate interactions. To test this hypothesis, the study will first establish a continuum theory guided by the thermodynamics of mixtures, i.e., by viewing material as a superposition of the solid, fluid and surface phases, through which the smeared pore-scale forces appear as macroscale adsorption stresses acting on the porous skeleton. Expressions of pore-scale forces will be then sought via molecular dynamics (MD) simulations and surrogate pore models. Specifically, simplified pore models will be developed based on Gibbs’ excess treatment of nanoconfined fluid films to link pore-scale forces induced by sorption with experimentally measurable quantities (i.e., adsorption isotherm). The pore model will be validated by MD simulations of nanopores subjected to fluid adsorption. These microscale forces will then be upscaled via statistical homogenization to complete the poromechanics framework. Finally, the theory will be applied to model the sorption-deformation behavior of amorphous cellulose interacting with water vapor. The prediction will be validated against experimental data and MD simulation results obtained from the same material system. The research will challenge the current paradigm of poromechanics where short-range interactions and surface forces within individual pores have been routinely neglected. If successful, the research will greatly expand our fundamental understanding on mechanics of active and soft porous materials.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.

该资助支持对软纳米多孔材料中吸附-变形耦合的基本理解的研究，该研究将开发相应的力学理论，旨在更好地预测复杂纳米多孔介质中的吸湿运动，并通过设计控制吸附引起的驱动，其中吸附是指吸附。离子与带电表面的结合具有特征孔径低于 100 nm 的软纳米多孔材料在自然界（例如纤维素、蛋白质）和工程应用中普遍存在。 （例如水泥、凝胶、纳米复合材料），由于其网络拓扑和界面相互作用产生的纳米限制效应，这些材料在吸收/解吸流体/气体时通常表现出显着的膨胀/收缩。最近开发了仿生软纳米多孔材料，用于通过吸附驱动的快速可靠的执行器、传感器和人造肌肉。该项目将建立并验证基于孔隙尺度热力学和分子模拟的多尺度力学框架，用于预测纳米多孔材料吸附引起的应变。该项目还将开展一项涉及多尺度孔隙力学和新课程开发的教育计划。通过利用纳米工程材料的兴奋点，并利用参与机构的卓越创新和教育基础设施，开展大学预科推广。这项研究是由吸附和变形之间复杂耦合的假设驱动的。可以通过关注两个关键的孔隙尺度属性来预测，即固体吸附物相互作用引起的分离压力和表面张力。为了检验这一假设，该研究将首先建立由混合物热力学指导的连续介质理论，即，通过将材料视为固体、流体和表面相的叠加，弥散的孔隙尺度力表现为作用于多孔骨架的宏观吸附应力。然后，将通过分子动力学（MD）模拟和替代孔隙模型来寻找孔隙尺度力。具体来说，将基于吉布斯对纳米限制流体膜的过度处理来开发简化的孔隙模型，以将吸附引起的孔隙尺度力与实验可测量的联系起来。孔隙模型将通过受流体吸附作用的纳米孔的 MD 模拟来验证，然后通过统计放大这些微尺度力。最后，该理论将应用于模拟无定形纤维素与水蒸气相互作用的吸附变形行为，该预测将根据从同一材料系统获得的实验数据和MD模拟结果进行验证。将挑战当前的孔隙力学范式，在该范式中，单个孔隙内的短程相互作用和表面力通常被忽视。如果成功，该研究将极大地扩展我们对活性和软多孔材料力学的基本理解。该奖项。通过使用基金会的智力价值和更广泛的影响审查标准进行评估，NSF 的法定使命被认为值得支持。

项目成果

Buckling Mechanics Modulus Measurement of Anisotropic Cellulose Nanocrystal Thin Films

各向异性纤维素纳米晶体薄膜的屈曲力学模量测量

• DOI: 10.1021/acsapm.1c01514
• 发表时间: 2022-05
• 期刊: ACS Applied Polymer Materials
• 影响因子: 5
• 作者: Miller, Nolan A.;Li, Zhaofan;Xia, Wenjie;Davis, Chelsea S.
• 通讯作者: Davis, Chelsea S.

Microstructure and dynamics of nanocellulose films: Insights into the deformational behavior

纳米纤维素薄膜的微观结构和动力学：变形行为的见解

• DOI: 10.1016/j.eml.2021.101519
• 发表时间: 2022-01
• 期刊: Extreme Mechanics Letters
• 影响因子: 4.7
• 作者: Li, Zhaofan;Liao, Yangchao;Zhang, Yao;Zhang, Yida;Xia, Wenjie
• 通讯作者: Xia, Wenjie

Reactive Molecular Dynamics Study of Hygrothermal Degradation of Crosslinked Epoxy Polymers

交联环氧聚合物湿热降解的反应分子动力学研究

• DOI: 10.1021/acsapm.2c00383
• 发表时间: 2022-05-23
• 期刊: ACS Applied Polymer Materials
• 影响因子: 5
• 作者: Anas Karuth;Amirhadi Alesadi;Aniruddh Vashisth;W. Xia;B. Rasulev
• 通讯作者: B. Rasulev