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

近年来，无系绳微型游泳技术因其在微创医学和主动环境监测等方面的巨大应用潜力而引起了人们的广泛关注。微型游泳者最著名的运动之一是所谓的“珀塞尔游泳者”，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。在雷诺数较小的微尺度下，Purcell游泳器在几何上呈现出一维运动中最简单的分段结构。早期的数值和理论研究普遍基于相同的斯托克斯流假设，忽略了非线性和惯性的贡献。然而，在更仔细的检查下，许多微游泳者的实际流动条件并不满足忽略这些贡献的准则。另一方面，由于现有的微尺度制造方法难以以无创方式实现独立驱动铰链，因此，无系泊式Purcell游泳器和相关流动动力学的实验演示很少。本研究的成功将拓宽对微游泳者流动物理的理解，并通过实验证明了一种制造和控制无系绳微游泳者的新方法，用于研究其运动和流动动力学。本项目整合了研究生教育和课堂教学等教育组成部分。推广活动包括展示微游泳者的运动，以促进公众对STEM的兴趣。这项研究有两个主要目标。首先，一种独特的电微流体打印技术将定位和组装包含交联预聚物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，因此它将首次允许制造和光学驱动无系绳Purcell游泳器。其次，采用求解Navier-Stokes方程的高保真数值模拟方法研究微游泳者的purcell类运动，考察其在感兴趣雷诺数下对所涉及的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到一种新提出的X-swimmer (X-swimmer)，它是一种能够进行三维purcell式运动的微型swimmer （X-swimmer）。这项三维运动研究的结果将改变purcell类运动的范围，并为微游泳者运动和流动动力学的研究提供新的可能性。拟议研究的成功将导致未来更广泛的跨学科合作，以研究微型游泳者及其各种应用。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。

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.