Topological Guidance of Self-Propelled Janus Locomotors Along Solid Boundaries

这项研究研究的是自行式微型机器人。这些是超微型的移动车辆，大小是微米--一个红细胞或一粒花粉的尺寸。微型机器人通过消耗环境中存在的燃料，并将燃料的化学能转化为机械运动，在水等液体环境中独立旅行。由于其体积小，而且能够作为活动物质自行移动，自行式微型机器人在技术地平线上处于创新应用的中心。它们的医疗应用是最有前途的：微型机器人被设想能够与精子对接，并帮助它们向卵子移动以进行受精，导航血管以疏通动脉，并将药物运送到人体的目标位置，如肿瘤或患病的器官。引导微型机器人沿着规定的路径行驶的能力是必不可少的。虽然船上的导航系统可以用来响应外部指令，但本研究的重点是被动导航，即微型机器人对环境中的提示做出反应来引导自己。具体地说，这项研究研究了微型机器人如何被动地沿着墙上方固定高度的平面墙前进，或者绕过柱子。被动制导源于边界如何将化学能转化为机械运动，以及微型机器人如何与边界动态地相互作用。在教育方面，这笔补助金将资助两名研究生，一名理论研究生，一名实验研究生；他们的协同努力将拓宽他们各自的学术视野。一项针对纽约和新泽西两所当地高中的外展工作已经到位，这项研究将被整合到这些高中的研究课程经验中。这项研究研究了一个由球形粒子组成的运动模型，在粒子的一个表面涂上了铂催化剂，形成了一个双面的Janus粒子。铂作为一种燃料，在环境中与过氧化氢反应产生氧气和水。过氧化氢在活性表面上的反应在整个颗粒上的过氧化氢离子解离产物中产生梯度，进而产生电动推进力。虽然这一机制解释了这些Janus发动机在自由空间中的运动，但本研究检查了边界附近的电动推进，目的是从理论和实验上确定边界制导是否可能使用电动推进。将调查两个例子，Janus机车沿墙壁引导的能力，以及它们绕过(垂直)挂在墙上的柱子的能力。理论上，电流体动力学方程将被求解以获得确定的轨迹，并将进行布朗动力学模拟以了解导引态对热涨落的稳定性。还将在这两个表面拓扑学的指导上进行实验。这一奖项反映了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。

This research studies self-propelling microbots. These are ultra-miniaturized locomoting vehicles which are microns in size - the dimensions of a red blood cell or a grain of pollen. Microbots travel independently in a liquid environment such as water by consuming fuel present in the environment, and converting the chemical energy of the fuel into mechanical motion. Due to their small size and their ability to motor around by themselves as active matter, self-propelled microbots are at the center of innovative applications on the technological horizon. Their medical applications are the most promising: Microbots are envisioned to be able to dock with sperm and assist their movement towards an egg for fertilization, navigate blood vessels to unclog arteries, and ferry drugs to targeted sites in the human body such as tumors or diseased organs. The ability to steer microbots along prescribed pathways is essential. While on board guidance systems which respond to external instructions can be used for navigation, this research focuses on passive guidance in which the microbot responds to cues in its environment to guide itself. In particular, this research studies how a microbot can passively follow along a planar wall at a fixed height above the wall, or steer around a post. The passive guidance originates from how the boundary changes the conversion of the chemical energy into mechanical motion, and how the microbot interacts fluid dynamically with the boundary. Educationally, the grant will fund two graduate students, one on theory and one on experiments; their synergistic effort will broaden each of their academic horizons. An outreach effort to two local high schools, one in New York and one in New Jersey, is in place, and this research will be integrated into the research curriculum experience of these high schools.This research studies a model locomotor consisting of a spherical particle in which one face of the particle is coated with a platinum catalyst to form a two-faced Janus particle. The platinum reacts with hydrogen peroxide, as a fuel, in the environment to produce oxygen and water. The reaction of the peroxide on the active face creates gradients in the ionic disassociation products of the peroxide across the particle which in turn generates electrokinetic propulsive forces. While this mechanism explains the locomotion of these Janus engines in free space, this study examines the electrokinetic propulsion in the vicinity of boundaries and aims to determine theoretically and experimentally if boundary guidance is possible with electrokinetic propulsion. Two examples will be investigated, the ability of Janus locomotors to be guided along a wall, and their ability to circumnavigate a post attached (perpendicular) to a wall. Theoretically, the electrohydrodynamic equations will be solved to obtain deterministic trajectories, and Brownian dynamics simulations will be undertaken to understand the stability of guided states to thermal fluctuations. Experiments will also be undertaken on guidance on these two surface topologies.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.