Nourhani Amir, Karshalev Emil, Soto Fernando, Wang Joseph
Department of Nanoengineering, University of California San Diego, La Jolla, CA 92093, USA.
Department of Mechanical Engineering, Department of Biology, Biomimicry Research and Innovation Center, University of Akron, Akron, OH 44325, USA.
Research (Wash D C). 2020 Feb 21;2020:7823615. doi: 10.34133/2020/7823615. eCollection 2020.
Transient, chemically powered micromotors are promising biocompatible engines for microrobots. We propose a framework to investigate in detail the dynamics and the underlying mechanisms of bubble propulsion for transient chemically powered micromotors. Our observations on the variations of the micromotor active material and geometry over its lifetime, from initial activation to the final inactive state, indicate different bubble growth and ejection mechanisms that occur stochastically, resulting in time-varying micromotor velocity. We identify three processes of bubble growth and ejection, and in analogy with macroscopic multigear machines, we call each process a gear. Gear 1 refers to bubbles that grow on the micromotor surface before detachment while in Gear 2 bubbles hop out of the micromotor. Gear 3 is similar in nature to Gear 2, but the bubbles are too small to contribute to micromotor motion. We study the characteristics of these gears in terms of bubble size and ejection time, and how they contribute to micromotor displacement. The ability to tailor the shell polarity and hence the bubble growth and ejection and the surrounding fluid flow is demonstrated. Such understanding of the complex multigear bubble propulsion of transient chemical micromotors should guide their future design principles and serve for fine tuning the performance of these micromotors.
瞬态化学驱动的微马达是很有前景的用于微型机器人的生物相容性引擎。我们提出了一个框架，用于详细研究瞬态化学驱动微马达的气泡推进动力学及其潜在机制。我们对微马达活性材料和几何形状在其整个生命周期内（从初始激活到最终失活状态）变化的观察表明，存在随机发生的不同气泡生长和喷射机制，导致微马达速度随时间变化。我们识别出气泡生长和喷射的三个过程，并且类似于宏观多齿轮机器，我们将每个过程称为一个齿轮。齿轮1指的是在微马达表面脱离之前生长的气泡，而齿轮2中的气泡从微马达中跳出。齿轮3在本质上与齿轮2相似，但气泡太小，对微马达运动没有贡献。我们从气泡大小和喷射时间方面研究了这些齿轮的特性，以及它们如何对微马达位移产生影响。展示了调整外壳极性从而控制气泡生长、喷射以及周围流体流动的能力。对瞬态化学微马达复杂多齿轮气泡推进的这种理解应指导其未来的设计原则，并有助于微调这些微马达的性能。
