ISS: Thermophoresis in quiescent non-Newtonian fluids for bioseparations

存在许多自然和工业过程，其中悬浮在流体中的纳米级颗粒由于温度梯度而移动。这些粒子通常从热的区域移动到冷的区域。 这种现象被称为热泳，影响各种各样的过程，如用于检测病毒的药物输送和生物分离。 然而，目前对热泳的理解是有限的。 实验研究有相互矛盾的证据，使得很难确定驱动粒子运动的基本机制。 很少有研究考虑这些粒子在更复杂的流体和凝胶中的运动。解释实验数据的挑战在于，很难将热泳效应与由于温度变化引起的流体密度变化而产生的流体流动效应分开。为了克服这一限制，NSF-CASIS项目将把地面实验与国际空间站（ISS）上的微重力实验配对，在那里浮力驱动的流体流动可以忽略不计。 目标是确定在简单和复杂流体中驱动热泳的基本物理和化学，并通过优化流体特性来使用这些信息增强病毒分离平台。在疾病控制影响到每个人的时代，该项目将专注于开发增强型和强大的微流控病毒载量检测设备，该项目的目标是测量国际空间站上复杂流体中颗粒的热泳运动，以帮助设计下一代生物分离设备，用于无标记病毒载量检测。由于流体的热膨胀，重力驱动的浮力引起的再循环在微重力下受到抑制，这将使热泳的明确测量成为可能。该项目将使用多个粒子跟踪微观流变学（MPT），同时获得当地的热泳和流变数据。流体的范围将从可变离子强度的牛顿液体到具有不同程度的线性粘弹性或温度依赖性溶胶-凝胶转变的非牛顿流体。探针颗粒的尺寸和表面性质将改变，并且将跨越生物相关纳米颗粒（例如病毒）的性质。 地面实验将侧重于通过流变测试，颗粒合成和下游的微流体平台的重新设计，利用复杂的流体，以提高生物分离的流体特性选择。 该团队将与Tec Masters，Inc.一起设计这些实验。创建一个模块，远程执行所有操作的样本操作，精密加热，高速/高放大率成像，并在国际空间站上传输数据。 这一基础研究和首次展示了微流变学在空间中的应用，将影响流变学、胶体和界面科学以及生物分离社区，并培养博士后、研究生和本科生研究人员。通过这些基础和应用实验来改善地球上的生命的承诺将被纳入K-12学生和代表性不足的学生群体的外联活动中。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

There are many natural and industrial processes where nanoscale particles suspended in a fluid move as a result of a temperature gradient. These particles generally move from hot to cold regions. This phenomenon, which is known as thermophoresis, affects a wide variety of processes, such as drug delivery and bioseparations utilized for detecting viruses. However, the current understanding of thermophoresis is limited. Experimental studies have conflicting evidence, making it difficult to determine the fundamental mechanisms that drive particle motion. Very few studies have considered the motion of these particles in more complex fluids and gels. The challenge in interpreting experimental data is that it is difficult to separate effects of thermophoresis from effects of fluid flow arising from variations in the fluid density owing to variations in temperature. To overcome this limitation, this NSF-CASIS project will pair terrestrial experiments with those in microgravity onboard the International Space Station (ISS) where buoyancy-driven fluid flow is negligible. The goals are to determine the fundamental physics and chemistry driving thermophoresis in simple and complex fluids and to use this information for enhancing viral separation platforms by optimizing fluid properties. In an era when disease control affects everyone, this project will focus on developing enhanced and robust microfluidic viral-load detection devices.The objective of this project is to measure the thermophoretic motion of particles in complex fluids on the ISS to aid in the design of next-generation bioseparations devices for label-free viral load detection. Gravity-driven buoyancy-induced recirculation due to thermal expansion of the fluid is inhibited in microgravity, which will enable unambiguous measurements of thermophoresis. The project will use multiple particle tracking microrheology (MPT) to simultaneously obtain local thermophoretic and rheological data. Fluids will range from variable ionic strength Newtonian liquids to non-Newtonian fluids with varying degrees of linear viscoelasticity or a temperature dependent sol-gel transition. The size and surface properties of probe particles will be changed and will span properties of biologically relevant nanoparticles, such as viruses. Terrestrial experiments will focus on fluid property selection through rheological testing, particle synthesis, and downstream redesign of microfluidic platforms utilizing complex fluids to enhance bioseparations. The team will design these experiments with Tec Masters, Inc. to create a module that remotely performs all operations of sample manipulation, precision heating, high-speed/high-magnification imaging, and data transfer on the ISS. This basic research and first demonstration of the utility of microrheology in space will impact the rheology, colloid and interfacial science, and bioseparation communities and train postdoctoral, graduate and undergraduate researchers. The promise for enhancing life on Earth through these fundamental and applied experiments will be incorporated into outreach activities for K-12 students and underrepresented student populations.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.