液滴蒸发过程及其对纳米颗粒自组装构型的影响机制研究

The colloidal crystal, which is formed by patterned nanoparticles, has broad application prospects. Its fabrication is a great challenge in the nanomanufacturing. The conventional techniques are difficult to meet the requirements. As a simple and low cost technique, the Evaporation-Induced Self-Assembly (EISA) can fabricate high-quality and large area colloidal crystals using evaporating liquid droplets, and thus has been considered to be one of the most potential techniques for the preparation of colloidal crystals. However, EISA still can not meet the requirements of modern science and technology due to its existing problems. Knowing the self-assembling mechanism of nanoparticles in EISA is the key to solve these problems. This project is to explore the structures of the temperature field and the flow field inside drying droplets by combining the direct observations on the surface temperature and the internal flow of the droplets, the evaporation theory, the fluid dynamics and the numerical techniques. Then, considering also the measurements of the nanoparticle movement in the droplets, the surface physical chemistry and the colloidal dynamics, the effects of the droplet evaporation on the nanoparticle movement will be studied, the self-assembling mechanism of nanoparticles in EISA can be revealed, and the technologies and methods to improve the quality and the reliability of colloidal crystals can be explored. The results can be useful to reveal the formation mechanism of the nanostructured materials, and thus has important scientific significance and academic value to establish and improve the theory and technology of nanomanufacturing.

纳米颗粒有序排列形成的胶体晶体有着广泛的应用前景，其制备技术是纳米制造中面临的巨大难题，传统的加工技术很难满足要求。由于具有制备简单，成本低廉，可制备高质量、大面积晶体等优点，利用蒸发液滴获得纳米颗粒有序排列的蒸发诱导自组装（EISA）被认为是未来胶体晶体制备最具潜力的技术之一。但目前的EISA技术仍存在诸多问题，尚不能满足现代科技对胶体晶体的需求。充分了解EISA中纳米颗粒自组装机制是解决这些问题的关键。本课题从蒸发液滴表面温度、液体流动实验观测出发，结合蒸发理论、流体力学和数值计算技术，探明蒸发液滴中温度场、流场结构，并结合液滴中纳米颗粒运动观测、表面物理化学和胶体动力学，研究液滴蒸发对纳米颗粒运动的影响，阐明EISA中的纳米颗粒自组装机理，探索提高胶体晶体质量和可靠性的工艺和途径。本课题的研究对于揭示纳米材料的形成机理，建立和完善纳米制造理论与技术具有重要的科学意义和学术价值。

纳米颗粒有序排列形成的胶体晶体有着广泛的应用前景，其制备技术是纳米制造中面临的巨大难题，传统的加工技术很难满足要求。由于具有制备简单，成本低廉，可制备高质量、大面积晶体等优点，利用蒸发液滴获得纳米颗粒有序排列的蒸发诱导自组装（EISA）被认为是未来胶体晶体制备最具潜力的技术之一。但目前的EISA技术仍存在诸多问题，尚不能满足现代科技对胶体晶体的需求。充分了解EISA中纳米颗粒自组装机制是解决这些问题的关键。本课题针对液滴蒸发过程，将红外测温技术、荧光技术与颗粒成像测速技术相结合，围绕蒸发液滴表面温度分布、液滴内部流场结构、液滴中颗粒运动及颗粒沉积等科学问题，探索蒸发液滴中纳米颗粒自组装机制。突破传统实验手段，成功研制了可用于蒸发液滴轮廓、液滴表面温度、液滴中颗粒运动、颗粒沉积构型等观测的在线探测平台。进一步，在实验新平台的基础上，结合理论分析和数值计算，研究了液滴蒸发稳态假设适用性条件，蒸发制冷、气相热传导、环境湿度等对液滴蒸发和颗粒沉积的影响，以及饱和蒸汽下液滴蒸发行为，揭示了液滴蒸发特性和颗粒沉积规律，并对超疏水基底制备及其上液滴蒸发进行了初步研究，可为蒸发诱导自组装技术提供理论指导。