All-Aqueous Printing of Viscoelastic Droplets in 3D Space

与二维(2D)图片的像素类似，体素--以小立方体或球体的形式--是三维(3D)对象的基本构件。原则上，可以精确地定义单个体素的位置、组成和属性以及体素-体素相互作用，以匹配生物组织的艺术性。实现体素相关生物打印将极大地扩展现有3D生物打印技术的能力，这些技术在很大程度上依赖于一维(1D)生物墨水细丝的组装。然而，在3D空间中按需生成、存储和组装单个液滴仍然是一个巨大的挑战。该项目旨在建立基础知识，并提供一种在3D空间中精确操纵粘弹性液滴的新方法。这些知识和工具将对粒子合成、胶囊化、小型化软机器人和组织工程产生积极影响。通过提供跨学科研究的机会和组织当地的科学活动，该项目将培养来自不同背景的学生成为软物质和复杂流体领域的下一代科学领导者。通过与当地高中的外展互动，PI将利用该项目产生的大量高速视频来增加STEM领域中代表不足的少数族裔学生的渠道。该项目的研究目标是阐明与屈服应力流体中的全水打印粘弹性液滴相关的非线性流体动力学。将开发一个打印平台，以实时研究液滴打印的动力学。此外，还将开发一种策略来独立控制油墨的粘度和松弛时间。使用这些工具和材料，将探索三个问题：(1)如何在没有界面张力的情况下产生圆度良好的粘弹性液滴？(2)打印喷嘴从粘弹性液滴中分离的机制是什么？(3)决定松弛液滴圆度的参数是什么？通过理论和模型的实验验证，将建立普遍的标度定律，以预测液滴保真度与印刷条件和油墨的非线性流变性的关系。最后，利用受控的聚合物膨胀，它将打印出由相互连接但可区分的不同性质的水凝胶颗粒组成的3D结构。这些研究有望帮助建立体素相关生物打印的基础科学。这一奖项反映了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。

Analogous to pixels of two-dimensional (2D) pictures, voxels –– in the form of small cubes or spheres –– are the basic building blocks of three-dimensional (3D) objects. In principle, the location, composition, and properties of individual voxels and voxel-voxel interactions can be precisely defined to match the artistry of biological tissues. Realizing voxelated bioprinting would dramatically expand the capability of existing 3D bioprinting technologies, which largely rely on the assembly of one-dimensional (1D) bio-ink filaments. However, it remains a grand challenge to generate, deposit, and assemble individual droplets on-demand in 3D space. This project seeks to establish the foundational knowledge and to provide a new way of precisely manipulating viscoelastic droplets in 3D space. The knowledge and tools will make a positive impact on particle synthesis, encapsulation, miniaturized soft robots, and tissue engineering. By providing opportunities for interdisciplinary research and organizing local scientific activities, this program will train students from diverse backgrounds to be next-generation scientific leaders in soft matter and complex fluids. Through outreach interactions with local high schools, the PI will leverage the vast number of high-speed videos generated from this project to increase the pipeline of underrepresented minority students in STEM fields.The research goal of this project is to elucidate the nonlinear fluid dynamics associated with all-aqueous printing viscoelastic droplets in yield-stress fluids. A printing platform will be developed to study the dynamics of droplet printing in real time. Moreover, a strategy will be developed to independently control the viscosity and relaxation time of inks. Using these tools and materials, three questions will be explored: (1) How to generate a viscoelastic droplet of good roundness without the help of interfacial tension? (2) What are the mechanisms for detaching the print nozzle from a viscoelastic droplet? (3) What are the parameters determining the roundness of a relaxed droplet? Corroborating experiments with theory and modeling, universal scaling laws will be developed to predict the dependence of droplet fidelity on printing conditions and the nonlinear rheological properties of inks. Finally, exploiting controlled polymer swelling, it will be printed 3D structures consisting of interconnected yet distinguishable hydrogel particles of different properties. These studies are expected to help establish the foundational science for voxelated bioprinting.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.