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

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。基于喷墨的增材制造技术已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板上并随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具有附加设计和材料灵活性的快速且有效的非接触式制造，但其具有诸如粗糙分辨率、缺乏粘附性、制造不一致性以及打印部件的机械性能的不确定性的缺点。这些不希望的影响是由于胶体液滴的液体性质引起的液滴放置误差、液滴扩散的不确定性和不均匀的存款分布。为了克服这些缺点，这项工作提出了一种新的基于冷冻的喷墨打印概念，该概念在冲击后冷冻胶体液滴，然后升华，消除了沉积过程中不期望的过度扩散、颗粒传输和流体运动。该项目的目的是提供一个更好的了解胶体液滴的动态和热行为的基本物理细节的影响，变形和冻结过程中，这支配存款分辨率和均匀性的冻结为基础的喷墨工艺。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。该项目还将提供广泛的教育和推广活动，包括多年的研究生/本科生研究计划，开发新的教学模块，以及为当地K-12学生提供的推广计划，特别是那些来自STEM领域代表性不足的群体的人。拟议的研究旨在推进对胶体液滴在新型冷冻中的动力学和热行为的基本理解，基于喷墨3D打印工艺。该提案设想了三个主要焦点：（i）定量表征胶体液滴在不同环境和表面条件下的冲击，变形和冷冻/固化过程中的动力学行为和热演化;（ii）提取相关的动力学和热时间尺度;（iii）检查存款形态与不同的环境温度，湿度，表面温度和疏水性。该项目将为一项长期研究计划奠定基础，该计划专注于开发基于冷冻的新型喷墨3D打印技术，为制造各种应用中的高质量功能结构量身定制。该奖项反映了NSF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。

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.