Acquisition of Flow Total Internal Reflection Fluorescence Video Microscopy System to Support Investigation of Nano- and Micro-Particle Transport and Surface Interaction

使用寿命超过预期寿命的老化设备应由调查员进行更换。该设备对表面附近的纳米和微小颗粒(胶体)的传输及其附着在表面上进行直接实时观察。我们关心表面附近的胶体传输，因为它控制着它们在多孔介质中的传输距离，范围从保护地下水资源不受病原体的影响到运送用于地下清理危险废物的新型工程纳米颗粒。尽管它在一系列环境中很重要，但我们目前预测胶体在环境多孔介质中传输距离的能力很差，这是因为在环境条件下，颗粒和表面往往相互排斥，因为两者都倾向于带负电荷。胶体表面斥力阻碍颗粒附着到表面(不利的附着条件)，除非表面上的纳米级电荷不均匀局部消除了斥力。替换设备将允许我们通过改变物理参数(如溶液速度、胶体大小和胶体密度)以及化学参数(如溶液pH、溶液离子强度以及表面矿物学和组成)来执行一系列胶体传输实验，从而确定表面纳米级电荷不均匀的性质。被替换的设备支持了五个由国家科学基金会资助的合作研究项目，培训了两名博士后和九名研究生研究人员，并通过30多种出版物传播新知识和理论，以及供研究人员和从业人员使用的胶体运输免费软件(Parti-Suite)。新设备将允许研究人员继续培养研究生和博士后研究人员，并通过研究、出版和提供免费软件来贡献新知识。该系统包括放置在倒置荧光显微镜平台上的流动室，带有高分辨率摄像头，以及用于精确无脉冲流动的微流控流动系统。现有的设备将支持私人投资和他的博士导师目前资助的研究，以及合作的私人投资和他的两个博士顾问，以及预期的未来合作奖项。杠杆传输实验和机械模拟阐明了表面上纳米级有吸引力的区域的大小和空间密度如何导致在其他相同的个体群体中发展快速和缓慢附着的胶体亚群。将其他相同的胶体分离成快速和缓慢附着的亚群被认为导致普遍观察到的偏离传统预期的胶体浓度随着距离源头的增加而指数下降。正在进行的研究将探索不完全孔尺度混合和胶体表面排斥在不利条件下胶体与表面相互作用中的交叉作用。设备赠款还将为犹他大学中学科学教学(MSSST)研究生项目的外展工作提供平台，该项目邀请初中和高中生物、化学和地球科学教师参加为期六周的暑期实习，最终形成教师制定的一系列适合年级的教案，教师将通过这些教案影响600多名学生。这项针对初中生的外展活动将由六名教师在2023年夏季进行培训。模拟能力将得到扩展，并通过Parti-Suite免费软件向公众提供。这个免费软件由五个模块组成，用于模拟粒子传输和表面相互作用。所有模块都使用图形用户界面进行数据输入和模拟输出，尽管所有数据和模拟也以文本和Excel文件的形式输出。约翰逊博士将继续通过面对面的研讨会和基于Zoom的指导来帮助研究人员采用这种免费软件。源代码将提供给用户。这一奖项反映了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。

Replacement of aging equipment that has served well beyond its expected lifetime is to be acquired by the investigator. The equipment performs direct real-time observations of nano- and micro-particle (colloid) transport near surfaces, and their attachment to surfaces. We care about colloid transport near surfaces because it governs their transport distance in porous media in contexts ranging from protecting groundwater resources from pathogens to delivery of novel engineered nanoparticles for subsurface cleanup of hazardous waste. Despite its importance in a range of contexts, our current ability to predict colloid transport distances in environmental porous media is poor, due to the fact that, under environmental conditions, particles and surfaces tend to repel one another as both tend to be negatively charged. Colloid-surface repulsion hinders particle attachment to surfaces (unfavorable attachment condition), except at locations where nanoscale charge heterogeneity on surfaces locally eliminates repulsion. The replacement equipment will allow us to determine the properties of nanoscale charge heterogeneity on surfaces by allowing us to perform arrays of colloid transport experiments by changing physical parameters such as solution velocity, colloid size, and colloid density, as well as chemical parameters such as solution pH, solution ionic strength, and surface mineralogy and composition. The equipment being replaced has supported five NSF-funded collaborative research projects, training of two post-doctoral and nine graduate student researchers, and dissemination of new knowledge and theory via more than thirty publications, and colloid transport freeware for utilization by researchers and practitioners (Parti-Suite). The new equipment will allow the investigator to continue to educate graduate students and post-doctoral researchers, and contribute to new knowledge through research, publication, and provision of freeware.The system includes a flow chamber placed on the stage of an inverted fluorescence microscope, with a high-resolution camera, and a microfluidic flow system for precise pulse-free flow. The existing equipment will support currently-funded research by the P.I. and his Ph.D. advisee, as well as a collaborating PI and two of his Ph.D. advisees, as well as anticipated future collaborative awards. Leveraged transport experiments and mechanistic simulations elucidate how sizes and spatial densities of nanoscale attractive domains on surfaces result in the development of fast- and slow-attaching colloid subpopulations in a population of otherwise identical individuals. Segregation of otherwise identical colloids into fast- and slow-attaching subpopulations is thought to cause an ubiquitously-observed deviation from the conventionally-expected exponential decreases in colloid concentration with increasing distance from source. Ongoing investigations will explore the intersecting roles of incomplete pore-scale mixing and colloid-surface repulson on the interactions of colloids with surfaces under unfavorable conditions. The equipment grant will also provide a platform for outreach efforts in the Secondary School Science Teaching (MSSST) graduate program at the University of Utah, which engages middle and high school biology, chemistry, and earth science teachers in six-week long summer internships that culminate in a teacher-developed series of grade-appropriate lesson plans through which teachers will impact over 600 students. This outreach to middle and high school students will be conducted by six teachers-in training in summer 2023. Simulation capabilities will be expanded and provided to the public via Parti-Suite freeware. This freeware consists of five modules for simulations of particle transport and surface interaction. All modules utilize a graphical user interface for data input and simulation output, although all data and simulations are also output as text and Excel files. Dr. Johnson will continue to assist researchers in adoption of the freeware via in-person workshops and Zoom-based instruction. The source codes will be made available to users.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.