CAREER: Programmable Negative Water Adsorption of Bioinspired Hygroscopic Materials

吸湿材料通常在局部相对湿度增加时吸水膨胀，在相对湿度降低时释放水分收缩。在树木中观察到一种违反直觉的现象，当当地环境干燥时，树木会储存水分，而当环境潮湿时，树木会耗尽水分。受这种自然现象的启发，研究者将开发一类具有负水吸附能力的新材料，这样当RH增加时，水就会被释放出来。该项目将探索设计具有可编程负水吸附特性的吸湿材料的机会。该研究有望阐明反直觉的水/气负吸附现象的潜在机制。这些知识将导致与动态调节材料特性和响应软凝聚态物质相关的突破，并揭示大自然如何设计不同的微/纳米流体系统来利用水蒸发作为能源。这项研究还将使开发新的低成本集水设备成为可能，这种设备可以在干燥的环境中自动收集水，而不使用电能。教育活动与研究相结合，促进K-12学生对STEM的兴趣，增加公众对科学概念的理解。教育活动包括开发可见和可触摸的学习工具包和竞赛，使当地学生和纽约人能够与最先进的科学进行互动。当具有独特的水响应驱动和空化特征的材料域被仔细整合时，可以实现负水吸附现象。一系列的吸湿材料将被制造出来，通过改变封闭几何和表面化学，系统地改变封闭水的空化行为和材料对水的响应性。使用这些材料/结构，封闭几何和表面化学将与承压水的空化行为相关联。此外，该研究将通过调整承压水的特性来编程吸湿材料的水响应驱动。通过整合具有不同水响应和水空化特性的材料领域，将开发出负水吸附材料。总体教育目标是向学生和公众传达自然水蒸发的概念和重要性。纽约城市大学（CUNY）的学生将通过实践学习活动来学习。研究者将为当地高中学生和教师举办一年一度的“蒸发能源挑战”，并在公共场所传播蒸发科学。研究者还将重新设计跨学科的研究生课程。期望的教育成果是点燃学生和公众对自然蒸发作为能源的潜力的兴奋，并吸引有才华和有动力的学生追求STEM职业。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。

Hygroscopic materials typically absorb water and swell when the local relative humidity (RH) increases and then release water and shrink when the RH decreases. A counterintuitive phenomenon has been observed in trees, where they store water when the local environment is dry and deplete water when it is humid. Inspired by this natural phenomenon, the investigator will develop a new class of materials with negative water adsorption capabilities, such that water is released when the RH increases. This project will explore the opportunities for designing hygroscopic materials with programmable negative water adsorption properties. The research is expected to elucidate the underlying mechanisms of the counterintuitive phenomenon of negative water/gas adsorption. This knowledge will lead to breakthroughs related to dynamically regulating material properties and responsive soft condensed matter and reveal how nature designs different micro/nanofluidic systems to harness water evaporation as an energy source. The research will also enable the development of new low-cost water harvesting devices that autonomously collect water in a dry environment without using electrical energy. Educational activities are integrated with the research to promote K-12 students’ interest in STEM and increase the public’s understanding of scientific concepts. The educational activities include developing visible and touchable learning kits and competitions, allowing local students and New Yorkers to interact with state-of-the-art science engagingly. The negative water adsorption phenomenon is achieved when domains of materials with distinctive water-responsive actuation and cavitation characteristics are carefully integrated. A range of hygroscopic materials will be fabricated such that the confined water cavitation behaviors and material water responsiveness are systematically varied through changes to the confining geometry and surface chemistry. Using these materials/structures, the confining geometry and surface chemistry will be correlated with the confined water cavitation behavior. Additionally, the research will program hygroscopic material water-responsive actuation by tuning the properties of confined water. Negative water adsorption materials will be developed by integrating the domains of materials with distinct water-responsive and water cavitation properties. The overarching educational goal is to communicate the concepts and importance of natural water evaporation to students and the public. The City University of New York (CUNY) students will be taught through hands-on learning activities. The investigator will host an annual “Evaporation Energy Challenge” for local high school students and teachers and communicate evaporation science in public venues. The investigator will also redesign an interdisciplinary graduate-level course. The desired educational outcome is to ignite the students’ and the public’s excitement about the potential of natural evaporation as an energy source and attract talented and motivated students to pursue STEM careers.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.