Programmable Surfaces by Scalable Self-assembly of Particles Printed by Two-photon Polymerization

具有微尺度特征的纹理表面具有自清洁、增强抓握和定向光散射等多种工程应用。然而，在大面积上制造高保真的纹理表面是一项挑战，更不用说质量控制、图案复杂性和特殊设备需求等问题了。该奖项支持无数多面体粒子自组装解决方案的基础研究，以实现广泛的微纹理图案。除了可以使用传统光刻技术制造的常见几何形状之外，该项目的独特创新在于使用双光子聚合来制造复杂形状的粒子，这使得微图案表面的自组装能够实现可调的面内和面外周期性和面外突起。所研究的自组装纹理表面可以被编程并实现可控的润湿性或用作涂层，特别是在有机光伏和可穿戴传感器等应用中对弯曲和/或微妙的基板具有吸引力。教育活动包括为小学生开发和实施粒子自组装学习模块，通过暑期实习接待一名来自当地西班牙裔社区大学的学生，并将自组装主题纳入结晶固体缺陷的研究生课程。利用三维打印技术，即双光子聚合，该项目将制造微尺度粒子，用于自组装成纹理表面。大约20万个粒子的阵列将被打印在固体衬底上，转移到充满液体的井中，然后通过沉淀、扩散、粒子间和粒子-衬底相互作用的平衡进行自组装。将研究不同几何形状的粒子，包括不同大小的四面体和正方形金字塔以及二元粒子系统，以获得在毫米尺度上形成的可调特征高度和周期性。利用光学显微镜获取粒子沿自组装时间运动的视频图像，并进行自动图像分析，以评估自组装表面的质量。将分析键和体序参数，以了解在不同加工条件下可以实现的均匀度，以及在这种自组装过程中产生的缺陷类型。理论研究将包括使用爱因斯坦-斯托克斯方程建模的布朗运动和使用DLVO原理建模的能量驱动力，以设计可能成功的自组装实验，然后与实验结果进行比较，以获得控制自组装机制的新知识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Textured surfaces with micro-scaled features have many engineering applications such as self-cleaning, enhanced gripping and directional light scattering, etc. However, it is challenging to manufacture textured surfaces over a large area with high fidelity, needless to mention the issues with quality control, pattern complexity and special equipment needs, etc. This award supports fundamental research in self-assembling of countless polyhedral particles in a solution to achieve a wide range of micro-textured patterns. Beyond common geometry that can be fabricated using conventional lithography techniques, the unique innovation of this project is the use of two-photon polymerization to fabricate particles of complex shapes, which enable tunable in-plane and out-of-plane periodicities and out-of-plane protrusions in the self-assembly of micro-patterned surfaces. The studied self-assembled textured surfaces can potentially be programmed and achieve controllable wettability or be used as coatings, especially attractive for curved and/or delicate substrates in applications such as organic photovoltaics and wearable sensors. The educational activities consist of developing and implementing a particle self-assembly learning module for elementary school students, hosting a student, via summer internship, from a local Hispanic community college, and incorporating the topic of self-assembly into a graduate course on defects in crystalline solids.Using a three-dimensional printing technology, namely, two-photon polymerization, this project will fabricate micro-scaled particles for self-assembly into textured surfaces. Arrays on the order of 200,000 particles will be printed on a solid substrate, transferred to a liquid-filled well, and then self-assembled through a balance of sedimentation, diffusion, interparticle and particle-substrate interactions. Particles of different geometries will be investigated including tetrahedrons and square pyramids of varying sized as well as binary particle systems, to obtain a tunable feature height and periodicity formed at a millimeter scale. An optical microscope will be utilized to acquire video images of particle motions along the self-assembling time with automated image analyses to evaluate the quality of the self-assembled surface. The bond and body order parameters will be analyzed to understand the degree of uniformity that can be achieved under different processing conditions, and the types of defects generated during such a self-assembly process. Theoretical studies will include the Brownian motion modeled using the Einstein-Stokes equation and the energetic driving force modeled using the DLVO principle to design self-assembly experiments that are likely to succeed, and then compared against experimental results to gain new knowledge of what governs the self-assembly mechanisms.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.