Biological Systems and Micromechanics, Singapore-MIT Alliance for Research and Technology, 138602 Singapore, Singapore.
Campus for Research Excellence and Technological Enterprise, 138602 Singapore, Singapore.
Proc Natl Acad Sci U S A. 2020 Mar 17;117(11):5671-5679. doi: 10.1073/pnas.1919363117. Epub 2020 Mar 3.
Microfluidic tools and techniques for manipulating fluid droplets have become core to many scientific and technological fields. Despite the plethora of existing approaches to fluidic manipulation, non-Newtonian fluid phenomena are rarely taken advantage of. Here we introduce embedded droplet printing-a system and methods for the generation, trapping, and processing of fluid droplets within yield-stress fluids, materials that exhibit extreme shear thinning. This technique allows for the manipulation of droplets under conditions that are simply unattainable with conventional microfluidic methods, namely the elimination of exterior influences including convection and solid boundaries. Because of this, we believe embedded droplet printing approaches an ideal for the experimentation, processing, or observation of many samples in an "absolutely quiescent" state, while also removing some troublesome aspects of microfluidics including the use of surfactants and the complexity of device manufacturing. We characterize a model material system to understand the process of droplet generation inside yield-stress fluids and develop a nascent set of archetypal operations that can be performed with embedded droplet printing. With these principles and tools, we demonstrate the benefits and versatility of our method, applying it toward the diverse applications of pharmaceutical crystallization, microbatch chemical reactions, and biological assays.
微流控工具和技术在操控液滴方面已经成为许多科学和技术领域的核心。尽管已经存在大量的流体操控方法，但很少利用非牛顿流体现象。在这里，我们介绍嵌入式液滴打印 - 一种在屈服应力流体中生成、捕获和处理液滴的系统和方法，屈服应力流体是指表现出极端剪切变稀的材料。这种技术允许在传统微流控方法根本无法实现的条件下操控液滴，即消除包括对流和固体边界在内的外部影响。正因为如此，我们相信嵌入式液滴打印为在“绝对静止”状态下对许多样品进行实验、处理或观察提供了一种理想的方法，同时还消除了微流控的一些麻烦方面，包括表面活性剂的使用和器件制造的复杂性。我们对模型材料系统进行了表征，以了解在屈服应力流体中生成液滴的过程，并开发了一套可以使用嵌入式液滴打印执行的原始典型操作。有了这些原理和工具，我们展示了我们的方法的优势和多功能性，并将其应用于药物结晶、微批量化学反应和生物分析等各种应用。
