CAREER: Dynamic characterization of acoustofluidic devices using living probes

声流体学是利用声波来操纵液体中的小物体或粒子。声学微流控装置在医学和生物学方面有很大的应用潜力，因为超声波是安全的，可以用来移动微小的物体而不接触它们。这些物体的大小可以从单个分子到生物细胞不等。然而，由于无法测量和比较其性能以确保一致的质量，声流体装置的使用受到限制。这个CAREER项目将使用活跃的、游动的藻类细胞来评估声流体装置的工作效果。游动微生物对环境变化的反应能力将被用于观察和测量形状复杂的设备中的超声波。这种新的测量方法可用于简化声学微流体装置的混合、分离、捕获和控制微观物体运动的测试。声波的研究也提供了一个独特的机会，通过他们对声音的基本理解和自然兴趣来吸引和激发学生和公众。CAREER项目将支持在华盛顿大学和圣路易斯地区开展有关波、声和振动的教学活动。本科生研究人员和实习教师将设计、制造和测试声学微流体装置，并为K-12学生制作教育材料。视频、演示和教学模块将在当地学校使用，为代表性不足的学生提供参与STEM的机会。这些主题的教育活动将被纳入该大学的学校伙伴关系研究所MySci项目，该项目覆盖了大约10万名K-12学生，是区域STEM教育的组成部分。不充分的计量是声流体学从实验室转化为实践的关键障碍。然而，声流体参数场（力、力势和压力）的定量预测具有挑战性，因为理想化的计算模型无法准确捕捉真实设备的复杂性（例如，制造公差和组件接口）。此外，目前的实验方法仅限于简单的几何形状，并且依赖于被动示踪粒子，这些示踪粒子不能随着条件的变化而对变化的场做出反应。CAREER项目的目标是利用游动细胞与超声波驻波的相互作用来阐明和量化复杂声流体装置的性能。藻类C. reinhardtii的细胞不断地探测它们的环境，在整个流体领域产生一个全面的、实时的声场图像。通过标定这些微游泳体（即建立其声物理性质和推进能力），可以将其空间分布的动态演变与场形状的演变相关联。该技术可用于表征性能并确定最佳操作条件。相反，这些场-粒子相互作用将为研究微游泳者如何响应外部力场提供机会。准确和快速的性能表征对于声流体学的进步至关重要，因此CAREER项目将加速实现这些技术的全部潜力。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。

Acoustofluidics is the use of sound waves to manipulate small objects or particles in liquids. Acoustic microfluidic devices have great potential for applications in medicine and biology because ultrasound, which is known to be safe, can be used to move tiny objects without touching them. These objects can range in size from individual molecules to biological cells. However, the use of acoustofluidic devices has been limited by an inability to measure and compare their performance to ensure consistent quality. This CAREER project will use active, swimming algae cells to assess how well acoustofluidic devices work. The ability of swimming microorganisms to respond to their changing environment will be exploited to see and measure ultrasound waves in devices with complicated shapes. This new measurement approach can be used to streamline testing of acoustic microfluidic devices for mixing, separation, trapping, and controlled motion of microscopic objects. The study of sound waves also presents a unique opportunity to engage and excite students and the general public through their basic understanding and natural interest in sound. The CAREER project will support the development of activities to teach about waves, sound, and vibrations at Washington University and in the St. Louis region. Undergraduate researchers and teacher interns will design, make, and test acoustic microfluidic devices, and create educational materials for K-12 students. Videos, demonstrations, and teaching modules will be used at local schools, providing opportunities to engage underrepresented students in STEM. Educational activities on these topics will be incorporated into the university's Institute for School Partnership MySci program, which reaches approximately 100,000 K-12 students and is integral to regional STEM education.Inadequate metrology is a critical barrier to the translation of acoustofluidics from the laboratory into practice. However quantitative prediction of acoustofluidic parameter fields (force, force potential, and pressure) is challenging, as idealized computational models fail to accurately capture the complexity of real devices (e.g., manufacturing tolerances and component interfaces). In addition, current experimental methods are limited to simple geometries and rely on passive tracer particles that cannot respond to the changing field as conditions vary. The goal of the CAREER project is to use the interactions of swimming cells with ultrasonic standing waves to elucidate and quantify the performance of complex acoustofluidic devices. Cells of the alga C. reinhardtii continuously probe their environment, yielding a comprehensive, real-time picture of the acoustic field throughout the fluid domain. By calibrating these micro-swimmers (i.e., establishing their acoustophysical properties and propulsive capability), the dynamic evolution of their spatial distribution can be correlated to the evolving field shape. This technique can be used to characterize performance and identify optimal operating conditions. Conversely, these field-particle interactions will provide opportunities to investigate how micro-swimmers respond to external force fields. Accurate and rapid performance characterization is critical to the advancement of acoustofluidics, and thus the CAREER project will accelerate realization of the full potential of these technologies.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.