ERI: Unraveling Multi-Phase Ink Shear-Thinning Flow Mechanism in Direct Ink Writing Process: Computational Fluid Dynamics Simulation and In-Situ Experimental Verification

直接墨水书写（DIW）作为一种敏捷的增材制造方法出现，能够将功能材料制造成三维结构。在DIW打印过程中，多相油墨结合了固体、液体和气相成分，引入了复杂的流体动力学，从而可以制造出具有增强性能的部件。潜在的应用包括电子、航空航天和生物技术。该工程研究启动（ERI）奖支持将DIW工艺参数与油墨性能联系起来的全面研究工作。如果成功，该项目将为用于基于挤压的3D打印的多相油墨的流变行为提供新的理解。其影响将超越研究成果，并为科学、技术、工程和数学（STEM）领域的研究生、本科生和代表性不足的群体提供有价值的教育。外展活动将促进更广泛的参与，并激励学生追求先进制造业的职业生涯。本研究项目旨在揭示多相油墨在DIW过程中的剪切-减薄流动机理。目前对多相油墨的认识主要依赖于宏观流变特性，导致宏观认识与微观流体动力学之间存在差距。通过三个研究任务，本研究试图通过发现油墨剪切变薄流变特性与DIW加工参数之间相互作用的基本知识来填补这一空白。任务1的重点是建立和实现多相油墨的计算流体动力学（CFD）模拟。Task 2使用已建立的模型来评估流变性能。如何准确地模拟各种油墨组分之间的相互作用并预测其流变性能，是一个需要解决的关键研究问题。任务3开发用于实验验证的原位传感。仿真模型将使用原位传感和制造后表征进行验证。流体动力学数据，包括流动轨迹、油墨速度和剪切速率，将使用基于粒子成像测速（PIV）的装置收集。CFD仿真与实验结果的对比为过程控制提供了新的思路。从这项研究中发现的新知识将促进DIW技术的广泛采用，并影响其他工程领域。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。

Direct ink writing (DIW) emerges as an agile additive manufacturing method capable of fabricating functional materials into three-dimensional structures. During the DIW printing process, multi-phase ink, which combines solid-, liquid-, and gas-phase ingredients, introduces complex fluid dynamics to allow for the fabrication of parts with enhanced properties. Potential applications include electronics, aerospace, and biotechnology. This Engineering Research Initiation (ERI) award supports a comprehensive research effort to link the DIW process parameters with ink property. If successful, the project will provide new understanding of the rheological behavior of multi-phase inks used for extrusion-based 3D printing in general. The impact will extend beyond the research outcomes and empower valuable education for graduate, undergraduate, and underrepresented groups in science, technology, engineering, and mathematics (STEM) fields. The outreach activities will promote broader participation and inspire students to pursue careers in advanced manufacturing. This research project aims to unravel the shear-thinning flow mechanism of multi-phase inks in the DIW process. The current understanding of multi-phase ink primarily relies on macroscopic rheological properties, resulting in a gap between macroscopic understanding and microscopic fluid dynamics. The effort seeks to fill in this gap by discovering the fundamental knowledge of the interaction between ink shear-thinning rheological properties and DIW processing parameters via three research tasks. Task 1 focuses on establishing and implementing computational fluid dynamics (CFD) simulation for multi-phase inks. Task 2 uses the established model to evaluate rheology properties. A key research question to be addressed is how to accurately simulate the interactions among various ink components and predict rheological properties. Task 3 develops In-situ sensing for experimental verification. Simulation models will be validated using in-situ sensing and post-manufacturing characterization. The fluid dynamics data, including the flow trajectory, ink velocity, and shear rate, will be collected using a particle imaging velocimetry (PIV)-based setup. The comparison between CFD simulations and experiments could provide new insights into process control. The new knowledge to be discovered from this research will facilitate broader adoption of the DIW technology and impact the other fields of engineering.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.