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

两种最常见的增强表面功能特性的方法是通过微尺度纹理和化学涂层。由于目前的方法同时应用这两种方法的能力有限，因此需要一种新的制造技术，以便可以在单一工艺中完成表面改性。一个潜在的候选者是自聚焦电流体动力微织构(SF-EMT)工艺。它使用电动力以逐滴方式操纵用于打印结构的喷墨，通过利用先前沉积的液滴和打印喷嘴之间的吸引力来产生多层纹理。可以使用各种油墨在印刷结构上嵌入不同的化学成分。SF-EMT的潜力将通过印刷大型露水收集器和微型电容器阵列来展示。SF-EMT将以更低的制造成本为高性能表面、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制作具有不同化学成分的表面纹理和图案的原型。该项目将为研究生和本科生提供多学科的研究机会。现有的体制机制和计划将被用来通知和吸引代表不足的少数族裔进入这些先进的制造业研究职位，并进一步增加对STEM相关职业的兴趣。SF-EMT的实现需要了解一种新发现的自聚焦机制，通过这种机制，喷气式飞机被吸引到以前沉积的特征。将通过实验和数值模拟相结合的方法来了解印刷过程不同阶段的动态、复杂的电荷和质量传递机制。重点是了解珠子在表面和其他珠子上的沉积，整个过程中溶剂的蒸发，以及电荷的消散。该工艺的实现还需要新的聚合物油墨的配方。通过利用数值模型来显著减少潜在的设计空间和要测试的油墨数量，将加快针对特定应用的油墨成分的调整。用于收集露水的油墨将使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。对于微型电容器阵列，将配制导电油墨和介电油墨。为了验证数值模型和进行工艺评估，将建造一个具有机器视觉的最先进的试验台，用于喷嘴位置控制、珠粒尺寸和溶剂挥发的现场测量、受控湿度和工艺参数的精确计算机控制。该奖项反映了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。

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.