EAGER: Numerical and Experimental Study of Purcell-Like Locomotion for Microswimmers

近年来，自由微泳者因其在微创医学、主动环境监测等领域的巨大应用潜力而引起人们的极大兴趣。微泳者最著名的运动之一是所谓的“Purcell游泳者”，它最初是由诺贝尔奖获得者爱德华·珀塞尔提出的，后来以他的名字命名。Purcell游泳者在几何上为雷诺数较小的微尺度上的一维运动提供了最简单的分段结构。早期的数值和理论研究普遍基于相同的Stokes流假设，忽略了非线性和惯性的贡献。然而，在更仔细的检查下，许多微泳运动员的实际流动条件不满足忽略这些贡献的标准。另一方面，由于用现有的微尺度制造方法以非侵入性的方式实现单独驱动的铰链的挑战，关于无绳索的Purcell游泳者和相关的流动动力学的实验演示很少。这项研究的成功将拓宽对微泳者流动物理的理解，并为研究微泳者的运动和流动动力学提供一种新的制造和控制微泳者的方法。该项目融合了研究生教育和课堂教学等教育内容。为促进STEM的公众利益，在外展活动中包括了微泳者的移动演示。这项研究主要有两个目的。首先，一种独特的电微流体打印技术将定位和组装包含可交叉连接的预聚体和颗粒嵌入水凝胶的多个液滴，以制造具有单独驱动铰链的微型游泳器，从而首次实现制造和光学驱动无绳索Purcell游泳器。其次，利用高保真数值模拟求解Navier-Stokes方程来研究微泳者的类Purcell运动，以考察雷诺数对所涉及流动物理的非线性和惯性影响。这项研究的两个部分都涉及对一种新提出的X-游泳运动员的研究，该运动员是一种能够像Purcell一样进行三维运动的微型游泳运动员。这一三维运动研究的结果将改变类Purcell运动的范围，并为研究微泳运动员的运动和流动动力学提供新的可能性。拟议研究的成功将导致未来在更广泛的社区中进行跨学科合作，研究微型游泳运动员及其各种应用。该奖项反映了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。

Untethered microswimmers have attracted many interests in recent years due to their great potential in various applications such as minimally invasive medicine and active environment monitoring. One of the most famous locomotion by micro-swimmers is the so-called “Purcell swimmer” which was first proposed by and later named after Nobel laureate Edward Purcell. The Purcell swimmer geometrically presents the simplest segmented structure for one-dimensional locomotion on microscale where the Reynolds number is small. Earlier numerical and theoretical studies were universally based on the same assumption of Stokes flow, which neglects the nonlinear and inertial contributions. However, under a more careful examination, actual flow conditions of many microswimmers do not satisfy the criterion to ignore those contributions. On the other hand, experimental demonstrations of untethered Purcell swimmers and associated flow dynamics were scarce due to the challenge of implementing individually-driven hinges in a non-invasive manner with existing fabrication methods for microscale. The success of this study will broaden the understanding of flow physics in micro-swimmers and experimentally demonstrate a new approach to fabricate and control untethered micro-swimmers for the study of their locomotion and flow dynamics. Education components such as graduate education and class teaching are integrated in this project. Demonstration of microswimmer locomotion is included in outreach events to promote public interests in STEM. There are two main goals in this research. First, a unique electromicrofluidic printing technique will position and assemble multiple droplets containing cross-linkable prepolymers and particle embedded hydrogels to fabricate micro-swimmers with individually driven hinges, thus it will allow to manufacture and optically drive untethered Purcell swimmers for the first time. Second, high-fidelity numerical simulation solving Navier-Stokes equations will be used to study Purcell-like locomotion of micro-swimmers to exam the nonlinear and inertial impact on the involved flow physics at the Reynolds number of interests. Both parts of the research involve the study of a newly proposed X-swimmer as a micro-swimmer capable of three-dimensional Purcell-like locomotion. The outcome of this study for three-dimensional locomotion will change the scope of Purcell-like locomotion and enable new possibilities in the study of microswimmer locomotion and flow dynamics. The success of the proposed research will lead to future interdisciplinary collaborations in a broader community for research in micro-swimmers and their various applications.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.