On the Mechanism and Utility of Laser-Induced Nucleation using Microfluidics

为什么用激光照射一些液体溶液会使它们结晶？造成这种现象的原因仍然是个谜。阐明光诱导成核的机制，即分子在结晶的最早阶段聚集在一起并组织起来的过程，是这一提议的目的。对这些机制的了解可以导致更绿色的工业过程，通过这些过程可以制造我们日常使用的各种材料和化学品，如染料和药品，从而节省能源并减少对大量化学溶剂的需求。除了减少制造晶体材料对环境的影响外，激光诱导成核还有可能在制造过程中更好地控制晶体形状和晶体中分子的排列，这些性能可以根据材料的特定应用进行优化。为了使绿色结晶成为本科和研究生教育的一部分，该项目将创建教育活动，培训来自不同背景的学生基于这种新的结晶方法设计解决方案，使其成为基础化学工程教育的固有部分。该研究计划将设计和研究预先选择的有机分子的微流控非光化学、激光诱导成核(NPLIN)。晶化成不同形态、不同晶型的分子，以及单步成核与两步成核的分子都将被检查，以了解它们在光场中诱导成核的机制。这项工作中将研究的三种不同的机制是：i)光学克尔效应，光可以使无序溶质团簇中的分子排列，从而诱导成核；ii)介电极化，其中光降低略低于临界的溶质团簇的能量；iii)胶体杂质粒子对光的吸收，导致形成诱导成核的纳米气泡。要做到这一点，需要设计与脉冲准直激光光束相耦合的高压微流控技术，并研究布洛芬、卡马西平和甘氨酸晶体的激光诱导结晶。微流控技术的应用将为NPLIN提供一种定量的实验方法，也可以区分单步成核和两步成核。这些研究发现将为将基本发现转化为实际应用奠定基础。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。

Why does shining a laser on some liquid solutions cause them to crystallize? The reasons for this phenomenon remain a mystery. Elucidating the mechanisms by which light can induce nucleation, the process by which molecules cluster together and organize during the earliest stages of crystallization, is the aim of this proposal. Understanding these mechanisms could result in “greener” industrial processes by which a wide range of materials and chemicals that we use every day, such as dyes and pharmaceuticals, are made, saving energy and reducing the need for large amounts of chemical solvents. In addition to reducing the environmental impact of manufacturing crystalline materials, laser-induced nucleation has the potential to provide better control over crystal shape and the arrangement of molecules in the crystals during the manufacturing process, properties that can be optimized for a specific application of the material. To make greener crystallization part of undergraduate and graduate education, the project would create educational activities that train students from diverse backgrounds to engineer solutions based on this new approach to crystallization, making it an inherent part of basic chemical engineering education.This research program will design and study microfluidic nonphotochemical, laser-induced nucleation (NPLIN) of preselected organic molecules. Molecules that crystallize into different morphologies, into different polymorphs, and that follow single-step versus two-step nucleation will each be examined to understand their light-field induced nucleation mechanisms. The three different mechanisms that will be investigated in this work are i) the optical Kerr effect by which light can align molecules in a disordered solute cluster and thereby induce nucleation, ii) dielectric polarization in which light lowers the energy of slightly sub-critical solute clusters, and iii) the absorption of light by colloidal impurity particles resulting in the formation of nanobubbles that induce nucleation. Doing so will require the design of high-pressure microfluidics coupled with a pulsed, collimated laser beam, and investigations of laser-induced crystallization of ibuprofen, carbamazepine, and glycine crystals. The use of microfluidics will contribute a quantitative experimental methodology for NPLIN that can also distinguish single-step nucleation from two-step nucleation. The research discoveries will set the foundation for translating fundamental findings to practical applications.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.