Small-Amplitude AFM Studies of Nanoconfined Water

*非技术摘要*尽管水是环境中最普遍的液体，但它的性质仍然没有被很好地理解。在纳米技术的背景下，纳米水的行为是一个极具争议和重要的课题。纳米尺度的水在生物学和纳米技术中扮演着重要的角色，在生物学中，它决定着细胞中大分子的形状。在纳米技术中，工程师们正在开发新的设备，可以分析越来越小的水样，用于医学诊断。该奖项支持一项研究水的机械性质的项目，该水被限制在两个仅相隔1-20个水分子的表面之间。当水被限制在如此严密的地方时，它的行为与散装水截然不同。到目前为止，不同研究小组的实验得出了相互矛盾的结果。韦恩州立大学开发的一种新型原子力显微镜(AFM)将被用来在不同的条件下进行仔细的测量，例如离子浓度的变化或不同的限制表面，试图阐明限制在纳米尺度空间中的水的性质。该项目通过新的研究生跨学科材料科学计划和本科生生物医学物理计划与培训机会相结合。将参与这项研究的学生将接受仪器开发和最先进的纳米科学研究方面的培训。这项研究的结果将通过正在进行的推广工作进行交流，到目前为止，已接触到数百名初中生、教师和家长。*技术摘要*水作为生物系统的主要溶剂，其性质尚未得到充分了解，特别是在水仅限于纳米尺度空间的情况下。当水被限制在几个分子层时，连续介质模型被打破，并观察到振荡力分布。然而，测量纳米承压水的机械性能的实验却产生了相互矛盾的结果。该项目将使用韦恩州立大学开发的新型原子力显微镜(AFM)技术来研究纳米承压水层的力学和动力学。自制的原子力显微镜系统使用0.03纳米量级的超小振幅对承压水层的粘弹性性质进行线性测量。该项目将研究水在不同条件下的动态变化，包括溶解离子浓度、外加剪切、压缩速度、封闭表面的化学以及外部直流和射频电磁场的变化。后者旨在阐明纳米承压水中的极性和氢键对其粘弹性特性的影响。这项研究与韦恩州立大学的新教育计划相结合，包括新的跨学科材料科学研究生计划和新的本科生生物医学物理计划。通过这些项目和研究项目，研究生和本科生将接受最先进的仪器和纳米科学研究方面的培训。

****NON-TECHNICAL ABSTRACT****Although water is the most ubiquitous liquid in the environment, its properties are still not well understood. In the context of nanotechnology, the behavior of nanoscale water is a subject of great controversy and great importance. Nanoscale water plays an important role in biology, where it determines the shape of the macromolecules in our cells, and in nanotechnology, where engineers are developing new devices that can analyze ever smaller water samples for medical diagnoses. This award supports a project to study the mechanical properties of water confined between two surfaces that are only 1-20 water molecules apart. When water is confined to such tight places, it behaves quite differently from bulk water. So far, experiments by different research groups have yielded contradictory results. A novel Atomic Force Microscopy (AFM), developed at Wayne State University, will be used to conduct careful measurements under varied conditions, such as changes in ion concentration or different confining surfaces in an attempt to elucidate the properties of water confined to nanoscale spaces. This project is integrated with training opportunities through a new graduate interdisciplinary Materials Science program and undergraduate Biomedical Physics program. Students who will be involved in this research will be trained in instrument development and state-of-the-art nanoscience research. The results of this research will be communicated through ongoing outreach efforts, which have so far reached hundreds of middle and high school students, teachers and parents.****TECHNICAL ABSTRACT****The properties of water, as the primary solvent of biological systems, are not fully understood, especially in situations where water is confined to nanoscale spaces. When water is confined to only a few molecular layers, continuum models break down, and oscillatory force profiles are observed. However, experiments to measure the mechanical properties of nanoconfined water have yielded contradictory results. This project will use novel Atomic Force Microscopy (AFM) Techniques, developed at Wayne State University, to study the mechanics and dynamics of nanoconfined water layers. The home-built AFM systems use ultra-small amplitudes of order 0.03 nm to perform linear measurements of the viscoelastic properties of confined water layers. This project will study how the dynamics of water change under various conditions, including changes in dissolved ion concentrations, applied shear, compression speeds, chemistry of confining surfaces, and external DC and RF electromagnetic fields. The latter is intended to elucidate the role of polarity and hydrogen bonding in nanoconfined water on its viscoelastic characteristics. This research is integrated with new educational programs at Wayne State, including a new interdisciplinary Materials Science graduate program and a new undergraduate Biomedical Physics program. Through these programs and this research projects graduate and undergraduate students will be trained in state-of-the-art instrumentation and nanoscience research.