Multigear Bubble Propulsion of Transient Micromotors

Abstract

<jats:p>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.</jats:p>

Medical Micro/Nanorobots in Precision Medicine

“…[36][37][38] On the other hand, atomic layer deposition-based coatings (parylene, titanium oxide, silicon oxide) were used to cover most of the reactive surface except for a small opening, thus reducing the exposed reactive area. [39,40] The advantage of these methods is that there are many different types of commercially available microtemplates ranging from polymeric to metallic beads, with more recent examples of the use of biological and bioinspired templates. [41][42][43] Other designs with more complex structures, such as microcoils or sophisticated geometries have been built using advanced techniques, including 3D printing, [44][45][46][47][48] glancing angle deposition, [49][50][51][52] and rolled-up lithography.…”

Enhanced Light-Harvesting Efficiency and Adaptation: A Review on Visible-Light-Driven Micro/Nanomotors

“…To enhance the drive performance, controllability, and environmental suitability of micro/nanomotors, different types of input energies, e.g., chemical, magnetic, light, thermal, electric, and acoustic energies, were used to drive and control their motion. To date, different propulsion mechanisms have been used in micro/nanomotor: (1) self-electrophoresis [ 10 ] and self-diffusiophoresis [ 11 ] in chemically powered motors, (2) bubble propulsion [ 12 , 13 ], (3) thermophoresis [ 14 ], (4) magnetic field propulsion [ 15 , 16 ], (5) electrophoresis [ 17 ], (6) light-driven propulsion [ 18 , 19 ], and (7) acoustophoresis [ 20 , 21 ]. Among all abovementioned input energies, light energy is clean and has unique advantages.…”

Electrochemistry‐Based Light‐Emitting Mobile Systems

“…In general, two main types of self‐propulsion mechanisms can be distinguished: bubble propulsion and phoretic motion. In the first case, bubbles are formed on the catalytically active site, and their detachment generates motion, [26,27] whereas in the phoretic mechanism case, swimmers are propelled by a self‐generated local gradient. The first design of a self‐propelled particle was based on the catalytic decomposition of hydrogen peroxide on Pt [28] .…”