Real-time, Acoustic Tuning of the Rheology of Shear-Thickening Suspensions

工业过程中使用的许多流体都是剪切增稠的。也就是说，它们被迫流动得越快，粘性就越大。这一特点使它们的使用和操作成本高昂，需要大量的能源，并损坏加工设备。这项研究将确定低成本和节能的技术，使剪切增稠流体的粘性降低，从而使它们更容易和有效地使用。实验旨在表明，声波（超声波）可以以可控的方式产生，以调节和降低剪切增稠流体的粘度。这种粘度的降低将导致更少的能量消耗在移动和处理流体。这项工作的成功可以促进许多重要的制造过程，包括自修复材料的设计和3D打印应用。研究表明，通过对流动施加正交扰动可以控制和减轻剪切增厚。以前的研究主要是利用胶体悬浮液的电和磁特性来调节剪切增厚，这只对具有这些独特特性的颗粒有用。边界驱动的剪切流也被研究过，但在制造环境中不是标准的。因此，在被动颗粒的剪切增稠悬浮液的压力驱动流动中，迫切需要证明远程粘度调节。目前尚不清楚的是，如何在粒子水平上对压力驱动的流动进行远程扰动，从而打破力链，从而在可扩展的体系结构中实现，从而可以在宏观尺度上调整粘度，从而促进制造过程。我们将用双轴体声波强迫诱导正交扰动来使胶体悬浮液减稠。通过描述系统响应和胶体链的微观结构，我们将回答剪切力链如何在压力驱动的流动中断裂的基本问题。流体的远程扰动和减稠对于实现剪切增稠流体（自修复材料、喷墨打印、3D打印等）的许多令人兴奋的工程效益至关重要。除非剪切增稠悬浮液的制造和加工能够以一种热力学和经济高效的方式进行管理，并且对设备的损害最小，否则这些好处无法实现。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。

Many fluids used in industrial processes are shear-thickening. That is, they become more viscous the faster they are forced to flow. This feature can make their use and manipulation costly, require significant energy, and damage processing equipment. This research will identify low cost and energy efficient techniques for making shear-thickening fluids less viscous so that they can be more easily and efficiently used. Experiments are aimed at showing that acoustic (ultrasound) waves can be generated in a controlled fashion to tune and reduce the viscosity of shear-thickening fluids. This viscosity reduction will result in less energy consumption in moving and processing of the fluid. The success of this work could facilitate many important manufacturing processes, including the design of self-healing materials and 3D printing applications.It has been shown that shear thickening can be controlled and mitigated by applying an orthogonal perturbation to the flow. Previous studies have largely used electrical and magnetic properties of colloidal suspensions to tune shear thickening, which is only useful for particles with these unique properties. Boundary-driven shear flows have also been studied, but are not standard in manufacturing contexts. Thus there is an urgent unmet need to demonstrate remote viscosity tuning in pressure-driven flows of shear-thickening suspensions of passive particles. What is currently unknown is how remote perturbation of pressure-driven flows at the particle level to break force chains can be implemented in a scalable architecture that can tune viscosity on macroscopic scales and thus facilitate manufacturing processes. We will de-thicken colloidal suspensions by inducing orthogonal perturbations with biaxial bulk-acoustic-wave forcing. By characterizing both the systemic response and the microscale structure of the colloidal chains, we will answer the fundamental question of how shear-induced force chains can be broken in pressure-driven flow. Remote perturbation and de-thickening of fluids is important to realizing the many exciting engineering benefits of shear-thickening fluids (self-healing materials, inkjet printing, 3D printing, etc.). These benefits cannot be achieved unless the manufacturing and processing of shear-thickening suspensions can be managed in a way that is thermodynamically and economically efficient and is minimally damaging to equipment.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.