Effect of Electrostatic Fields on Self-Assembly at Surfaces

静电场对表面自组装的影响

• 批准号: 0827822
• 负责人: Nicholas Melosh
• 金额: $ 20万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0827822&HistoricalAwards=false
• 关键词: Effect; Electrostatic; Fields; Self; Assembly

CBET-0827822MeloshSelf-assembly at interfaces involves a delicate balance between charge, bonding strength, transport, and reversibility. External fields or non-uniform charge distributions can alter assembly behavior in surprising ways by accelerating, inhibiting or changing the assembly process. In particular, many molecular and biological species are themselves highly-charged systems which may also undergo significant conformational and electrostatic reconfiguration during reaction/assembly. This general problem of self-assembly in external fields and charge-redistribution during the assembly process has received little attention, yet is vital for the goals of top-down/bottom-up patterning or more traditional applications such as DNA microarrays and biosensors. This project will systematically measure how electric fields modulate self-assembly at interfaces, and develop a fully-vetted theoretical model. A new optical technique will be applied to monitor the spatial and temporal build-up of assembling species as well as the ionic double layer with single nanometer accuracy, providing new, quantitative information on the dynamics of highly charged species. In these experiments DNA serves as an ideal model system, as preliminary studies have shown that ionic strength and electric fields have some effect on assembly, but a complete theoretical model has not been established. DNA transport to the interface, hybridization, and melting kinetics will be studied as a function of length, potential field, mismatch locations, and charge density. The intellectual merit of this project is to elucidate how electric fields and ion distributions affect self-assembly mechanisms. Fundamentally, this work will fill a void in our understanding of how highly-charged species interact and react at surfaces under an external bias. While small ion and colloidal behavior in external fields are well-established areas, self-assembly under electric fields, the tendency of monomer reconfiguration during assembly, and the effect of force distribution on DNA within field gradients have not been explored. Mean-field and Brownian dynamics theoretical models will be developed that can replicate the results of these experiments, providing deeper insight into their mechanism. The broader impacts of this project include developing models to predict the hybridization and melting dynamics of DNA on surfaces, providing straight-forward error correction methods for nanomaterials assembly, educate graduate and undergraduate students, and to disseminate these findings. Development of new methods to control interfacial activity is important for separations, bio-fouling, DNA-array technology and coatings. A full understanding of the interplay between assembly and fields will allow design of pulse algorithms and conditions through which to greatly accelerate DNA hybridization while reducing mis-matches and cross-contamination, a critical problem for commonly used DNA microarrays, and can be implemented in a number of applications. These results will be widely shared with other researchers, foremost through development of a website with free public access to the codes and protocols used. In addition to scientific and technological impact, this proposal incorporates an educational outreach component as well. Undergraduate research, curriculum development, scientific professional development, and tutoring elementary school students are an integral part of the research program.

CBET-0827822界面自组装涉及电荷、结合强度、传输和可逆性之间的微妙平衡。外场或不均匀的电荷分布可以通过加速、抑制或改变组装过程，以令人惊讶的方式改变组装行为。特别是，许多分子和生物物种本身就是高度带电的系统，在反应/组装过程中也可能经历重大的构象和静电重新配置。这种在外场中的自组装和组装过程中的电荷重新分布的普遍问题几乎没有受到关注，但对于自上而下/自下而上的图案化目标或更传统的应用，如DNA微阵列和生物传感器，却是至关重要的。这个项目将系统地测量电场如何调制界面上的自组装，并开发一个完全经过审查的理论模型。一种新的光学技术将被应用于以单纳米精度监测聚集物种和离子双层的空间和时间积累，为高电荷态物种的动力学提供新的定量信息。在这些实验中，DNA是一个理想的模型体系，因为初步研究表明离子强度和电场对组装有一定的影响，但还没有建立一个完整的理论模型。DNA向界面的传输、杂交和熔化动力学将作为长度、势场、失配位置和电荷密度的函数进行研究。这个项目的学术价值在于阐明电场和离子分布如何影响自组装机制。从根本上说，这项工作将填补我们对高电荷态物种如何在外部偏置下在表面相互作用和反应的理解上的空白。虽然外场中的小离子和胶体行为是公认的领域，但在电场下的自组装，组装过程中单体重组的趋势，以及场梯度内的力分布对DNA的影响还没有被探索。平均场和布朗动力学理论模型将被开发出来，可以复制这些实验的结果，为它们的机制提供更深入的见解。该项目的更广泛影响包括开发预测DNA在表面的杂交和熔化动力学的模型，为纳米材料组装提供直接的误差校正方法，教育研究生和本科生，并传播这些发现。开发控制界面活性的新方法对分离、生物污垢、DNA阵列技术和涂层具有重要意义。充分了解组装和场之间的相互作用将允许设计脉冲算法和条件，通过这些算法和条件可以大大加速DNA杂交，同时减少不匹配和交叉污染，这是常用DNA微阵列的一个关键问题，并可以在许多应用中实施。这些成果将与其他研究人员广泛分享，主要是通过开发一个网站，免费向公众提供所使用的代码和协议。除科学和技术影响外，该提案还纳入了教育宣传部分。本科生研究、课程开发、科学专业发展和辅导小学生是研究计划不可或缺的一部分。