Collaborative Research: Fluid Dynamics Foundations of Cell Printing

结构细胞打印（SCP），或打印组织基质中保存的细胞的三维结构，一直是一个令人着迷的想法。利用微米级的基于液滴的打印技术，SCP有望实现与单个细胞大小相当的细胞沉积分辨率。在体外实现这样的分辨率将解决组织工程中最基本的挑战之一，并在许多领域实现革命性的突破。尽管存在重大问题，特别是细胞能否在严酷的打印过程中存活下来，但SCP的可行性最近得到了证明。然而，尽管SCP的研究呈爆炸式增长，但这种技术仍处于起步阶段，许多关键问题仍未解决。最重要的是，设想的细胞沉积分辨率尚未实现，细胞活力需要提高。要解决这些问题，就必须彻底了解SCP过程。该项目的目的是研究基于喷墨的SCP工艺的关键步骤，即使用综合实验和建模方法，将细胞负载液滴打印到薄液体膜上，形成二维细胞图案。这一关键步骤的两个单元操作将被研究，即打印具有单个细胞的点（cell dot）和打印细胞系（cell line）。细胞点印刷的研究将集中在阐明装载细胞的液滴影响液膜的动力学上，重点是液滴的扩散和渗透行为以及细胞的应力演变，这决定了细胞沉积分辨率和细胞活力。细胞系打印的研究将集中在描述顺序打印的细胞负载液滴之间的相互作用以及这些相互作用如何影响液滴液膜冲击，液滴内细胞的应力，最终影响细胞沉积分辨率和细胞活力。知识价值：提出的研究是流体动力学涉及基于喷墨的SCP技术的先驱研究。在这里获得的见解将为SCP工艺的合理设计提供知识基础，以实现最佳的细胞沉积分辨率和细胞活力，从而有助于消除这种新技术发挥其最大潜力的关键障碍。通过描述SCP过程中独特的液滴和细胞动力学，例如微秒时间尺度下超强剪切流中的细胞动力学，本研究也将丰富液滴和细胞动力学的流体动力学理论。拟议的研究将受益于两个在细胞打印和多物理场模拟方面具有互补专业知识的pi之间的协同合作，并得到最先进的实验和计算设施的支持。更广泛的影响：该项目将与ppi所在院校的本科研究生教育密切相关。参与这个跨学科项目的学生将接触到不同的领域，如流体力学、细胞力学和生物工程。每年将有五名本科生参与这项研究。将利用各种资源，例如pi机构的少数族裔招募计划，从代表性不足的群体中招募学生参加该项目。研究成果将被制作成电影，用于K-12的外展活动，并提交给Efluid.com主办的流体运动/图像画廊。为了向外行传播研究成果，并帮助他们了解流体动力学研究在开发有用技术方面的重要性，我们将建立一个名为“细胞打印的书呆子一面”的网站。本网站将使用实验/电脑生成的图像和电影，向公众解释结构细胞打印中涉及的流体动力学。该网站将通过正式和非正式渠道向目标受众做广告。

0936235/0936238 Qiao/Xu Structural cell printing (SCP), or printing three dimensional structures of cells held in a tissue matrix, has long been a fascinating idea. Drawing on the micrometer resolution of droplet based printing techniques, SCP holds the promise of achieving cell deposition resolution comparable to the size of a single cell. Achieving such a resolution in vitro will resolve one of the most fundamental challenges in tissue engineering and enable revolutionary breakthroughs in numerous areas. Despite significant concerns, in particular whether cells can survive the harsh printing process, the feasibility of SCP has been demonstrated recently. However, despite the explosive growth of research in SCP, such a technique is still in its infancy and many critical issues remain unresolved. Most importantly, the envisioned cell deposition resolution has yet to be achieved and the cell viability needs to be improved. Addressing these issues necessitates a thorough understanding of the SCP process. The objective of this project is to investigate a key step in the ink jet based SCP process, i.e., printing cell laden droplets onto a thin liquid film to form two dimensional cell patterns, using an integrated experimental and modeling approach. Two unit operations of this critical step will be studied, namely, the printing of a dot featuring a single cell (cell dot) and the printing of a line of cells (cell line). The study of cell dot printing will focus on elucidating the dynamics of a cell laden droplet impacting a liquid film with an emphasis on the spreading and penetration behavior of the droplet and the stress evolution of the cell, which govern the cell deposition resolution and cell viability. The study of cell line printing will focus on delineating the interactions between sequentially printed cell-laden droplets and how these interactions affect the droplet liquid film impact, the stress of cells inside the droplets, and ultimately the cell deposition resolution and cell viability.Intellectual Merit: The proposed research is a pioneer study of the fluid dynamics involved in ink jet based SCP techniques. The insights gained here will provide a knowledge base for the rational design of SCP process to achieve optimal cell deposition resolution and cell viability, and thus will help remove critical barriers for this new technique to reach its fullest potential. By delineating the droplet and cell dynamics unique to the SCP process, e.g., the dynamics of cells in exceedingly strong shear flows at microsecond time scale, this research will also enrich the fluid dynamics theories of droplet and cell dynamics. The proposed research will benefit from the synergistic collaboration between two PIs with complementary expertise in cell printing and mutliphysics simulations, and is supported by state-of-the-art experimental and computing facilities.Broader Impacts: The project will be tied closely to the undergraduate graduate education at the PIs home institutions. Students participating in this interdisciplinary project will be exposed to diverse fields such as fluid dynamics, cell mechanics and bioengineering. Five undergraduate students will be involved in the research each year. Various resources, e.g., the minority recruitment programs at the PIs institutions, will be utilized to recruit students from underrepresented groups to participate in this project. Research results will be developed into movies for use in K-12 outreach activities and for submission to the gallery of fluid motion/image hosted by Efluid.com. To help disseminate research to lay audiences and to help them appreciate the significance of fluid dynamics research in developing useful technologies, we will develop a website named The Nerdy Side of Cell Printing. This website will explain the fluid dynamics involved in structural cell printing by using experiment/computer generated images and movies that are easily understandable to the general public. The website will be advertised to the target audience via formal and informal channels.