Multi-Scale Multi-Material Printing of 3D Bead Arrays via Self-Focused Electrohydrodynamic Jets

增强表面功能特性的两种最常见的方法是通过微尺度纹理和化学涂层。由于目前的方法在同时应用这两种方法的能力上受到限制，因此需要一种新的制造技术，以便在单一过程中完成表面修饰。一种潜在的候选方法是自聚焦电流体动力微纹理（SF-EMT）工艺。它利用电力来操纵喷墨，以一滴一滴的方式打印结构，利用先前沉积的液滴和喷墨之间的吸引力来产生多层纹理。各种油墨可用于在印刷结构上嵌入不同的化学物质。SF-EMT的潜力将通过打印大型露珠收集器和微电容器阵列来证明。SF-EMT将在降低制造成本的同时，为高性能表面、表面改性和微结构打开大门。它的简单性和多功能性将允许快速原型的表面纹理和不同的化学图案。本项目将为研究生和本科生提供多学科研究机会。现有的制度机制和项目将被利用来告知和吸引未被充分代表的少数民族从事这些先进的制造业研究职位，并进一步提高对STEM相关职业的兴趣。SF-EMT的实现需要理解一种新发现的自聚焦机制，通过这种机制，射流被先前沉积的特征所吸引。将实验和数值模拟相结合，以了解印刷过程中不同阶段的动态、复杂的电荷和质量传递机制。重点将是了解珠在表面上和其他珠上的沉积，整个过程中溶剂的蒸发，以及电荷的耗散。该工艺的实现还需要新型聚合物油墨的配制。通过利用数值模型，可以大大减少潜在的设计空间和要测试的油墨数量，从而加快特定应用的油墨成分调整。用于收集露珠的墨水将用纳米添加剂和表面活性剂进行改性，以在沉积的珠子上产生纳米皱纹和纹理，从而产生多尺度纹理。对于微电容器阵列，将配制导电和介电油墨。将建立一个最先进的测试平台，用于喷射位置控制，珠粒尺寸和溶剂蒸发的原位计量，控制湿度，以及精确的计算机控制过程参数，以验证数值模型和过程评估。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。

The two most common ways for enhancing the functional properties of a surface are through micro-scale texturing and chemical coatings. Since current methods are limited in their ability to apply both of these methods simultaneously, a novel manufacturing technique is required so that surface modifications can be done in a single process. One potential candidate is a Self-Focused Electrohydrodynamic Micro-Texturing (SF-EMT) process. It uses electric force to manipulate an ink jet for printing structures in a droplet-by-droplet fashion to produce multilayer textures by utilizing the attraction between the previously deposited droplets and the printing jet. A variety of inks can be used to embed different chemistries on the printed structure. The potential of SF-EMT will be demonstrated by printing large-scale dew-collectors and micro-capacitor arrays. SF-EMT will open doors to high-performance surfaces, surface modifications and micro-structures at reduced manufacturing costs. Its simplicity and versatility will allow for rapid prototyping of surface textures and patterns with varying chemistries. Multidisciplinary research opportunities for graduate and undergraduate students will be made available through this project. Existing institutional mechanisms and programs will be leveraged to inform and attract underrepresented minorities to these advanced manufacturing research positions, and to further increase interest in STEM related careers.The realization of SF-EMT requires the understanding of a newly discovered self-focusing mechanism by which the jet is attracted to previously deposited features. A combination of experiments and numerical modeling to understand the dynamic, complex charge and mass transfer mechanisms at the different stages of the printing process will be investigated. Emphasis will be on understanding the deposition of beads on a surface and on top of other beads, the evaporation of the solvent throughout the process, and the dissipation of electrical charges. The realization of the process also requires the formulation of new polymeric inks. Tuning of ink composition for the specific applications will be expedited by leveraging the numerical models to significantly reduce the potential design space and the number of inks to be tested. Inks for dew-collection will be modified with nano-additives and surfactants to create nano-wrinkles and texture on the deposited beads resulting in multi-scale textures. For micro-capacitor arrays, conductive and dielectric inks will be formulated. A state-of-the-art testbed with machine vision for jet position control, in-situ metrology of bead size and solvent evaporation, controlled humidity, and precise computer control of the process parameters will be built for validation of the numerical models and for process assessment.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.