ERI: Understanding the Dynamic and Thermal Behaviors of Colloidal Droplets Toward a Novel Freezing-based Inkjet Printing Concept

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。基于喷墨技术的添加剂制造技术已被广泛用于制造复杂和先进的结构。传统的喷墨3D打印通过将胶体液滴喷射到基材上，然后蒸发和沉积来创建逐层结构。虽然这种喷墨技术可以提供快速高效的非接触式制造，具有额外的设计和材料灵活性，但它存在诸如分辨率低、缺乏附着力、制造不一致以及打印部件的机械性能不确定等缺点。这些不受欢迎的影响源于液滴放置错误、液滴扩散的不确定性以及由于胶体液滴的液体性质而导致的沉积分布不均匀。为了克服这些缺点，本工作提出了一种新颖的基于冷冻的喷墨打印概念，该概念在撞击后升华时冻结胶体液滴，消除了沉积过程中不必要的扩散、颗粒传输和流体运动。该项目旨在更好地了解胶体液滴在冲击、变形和冻结过程中的动态和热行为的基本物理细节，这些行为控制着基于冷冻的喷墨过程的沉积分辨率和一致性。所开发的知识在航空航天、医疗保健、生物医学和汽车行业具有潜在的应用价值。该项目还将提供广泛的教育和推广活动，包括多年研究生/本科生研究计划，开发新的教学模块，以及为当地K-12学生，特别是来自STEM领域代表性不足的群体的学生提供扩展计划。拟议的研究旨在促进对新型冷冻喷墨3D打印过程中胶体液滴的动态和热行为的基本了解。该提案设想了三个主要重点：(I)定量描述不同环境和表面条件下胶体液滴在冲击、变形和冻结/凝固过程中的动态行为和热演化；(Ii)提取相关的动态和热时间尺度；(Iii)研究不同环境温度、湿度、表面温度和疏水性下的沉积形貌。该项目将为一项长期研究计划奠定基础，该计划专注于开发新型冷冻喷墨3D打印技术，该技术专为制造各种应用中的高质量功能结构而定制。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Inkjet-based additive manufacturing technology has been widely used for manufacturing complex and advanced structures. Conventional inkjet 3D printing creates layer-by-layer structures by jetting colloidal droplets onto a substrate with subsequent evaporation and deposition. While this inkjet technology can provide fast and efficient non-contact manufacturing with additional design and material flexibilities, it suffers from drawbacks such as coarse resolution, lack of adhesion, manufacturing inconsistency, and uncertainty in mechanical properties of printed parts. These undesired effects arise from droplet placement errors, uncertainty in droplet spreading, and uneven deposit distribution, due to the liquid nature of the colloidal droplets. To overcome these disadvantages, this work proposes a novel freezing-based inkjet printing concept that freezes the colloidal droplets upon impact followed by sublimation, eliminating the undesirable overspreading, particle transport, and fluid motions during deposition. The project aims to provide a better understanding of the fundamental physical details of the dynamic and thermal behaviors of colloidal droplets during the impact, deformation, and freezing processes, which govern the deposit resolution and uniformity of the freezing-based inkjet process. The knowledge developed has potential applications in the aerospace, healthcare, biomedical, and automotive industries. The project will also provide a wide range of educational and outreach activities, including a multi-year graduate/undergraduate research program, development of new teaching modules, and an outreach program for local K-12 students, especially those from groups underrepresented in STEM fields.The proposed research seeks to advance the fundamental understanding of the dynamic and thermal behaviors of colloidal droplets in the novel freezing-based inkjet 3D printing process. The proposal envisions three major foci: (i) quantitatively characterize the dynamic behaviors and thermal evolutions of colloidal droplets during impact, deformation, and freezing/solidification processes under different ambient and surface conditions; (ii) extract the associated dynamic and thermal time scales; and (iii) examine the deposit morphologies with varying ambient temperature, humidity, surface temperature, and hydrophobicity. This project will establish the foundation for a long-term research program focused on the development of the novel freezing-based inkjet 3D printing technique tailored for fabricating high-quality functional structures in various 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.