How to Make a Fast, Efficient Bubble-Driven Micromotor: A Mechanical View

Abstract

Micromotors, which can be moved at a micron scale, have special functions and can perform microscopic tasks. They have a wide range of applications in various fields with the advantages of small size and high efficiency. Both high speed and efficiency for micromotors are required in various conditions. However, the dynamical mechanism of bubble-driven micromotors movement is not clear, owing to various factors affecting the movement of micromotors. This paper reviews various factors acting on micromotor movement, and summarizes appropriate methods to improve the velocity and efficiency of bubble-driven micromotors, from a mechanical view. The dynamical factors that have significant influence on the hydrodynamic performance of micromotors could be divided into two categories: environment and geometry. Improving environment temperature and decreasing viscosity of fluid accelerate the velocity of motors. Under certain conditions, raising the concentration of hydrogen peroxide is applied. However, a high concentration of hydrogen peroxide is not applicable. In the environment of low concentration, changing the geometry of micromotors is an effective mean to improve the velocity of micromotors. Increasing semi-cone angle and reducing the ratio of length to radius for tubular and rod micromotors are propitious to increase the speed of micromotors. For Janus micromotors, reducing the mass by changing the shape into capsule and shell, and increasing the surface roughness, is applied. This review could provide references for improving the velocity and efficiency of micromotors.

A Review of Fast Bubble-Driven Micromotors Powered by Biocompatible Fuel: Low-Concentration Fuel, Bioactive Fluid and Enzyme

“…Reviews have variously focused on the physical strategies [ 41 ], fabrication techniques [ 42 ], and specific applications [ 36 , 43 , 44 ]. Additionally, several publications about the moving speeds of bubble-driven micromotors have been reported [ 16 , 45 ]; however, few discuss the motion performance with biocompatible fuels.…”

“…Our previous studies have underlined the important role of fuel concentrations in motor locomotion [ 45 , 46 ]. The toxicity associated with concentrated fuel has hindered practical applications of micromotors, especially in the biomedical area [ 43 , 47 ].…”

Mg-Based Micromotors with Motion Responsive to Dual Stimuli

“…This suggests that the as-prepared Mg-based micromotor may be taken as an example to address its intrinsic drawbacks of uncontrollable propulsion and limited motion lifetime arising from its self-consuming features. Although the H 2 O 2 concentration used here is not in the nontoxic physiological range of less about 50 μ M, the “fuel” concentration for the effective motor driving can be reduced via enhancing catalytic reaction activities, regulating motor structures, and so on [ 32 , 33 ]. Moreover, the LCST of the hydrogel can be adjusted to fit the body temperature range by copolymerization [ 34 , 35 ].…”

Geometry Design, Principles and Assembly of Micromotors

“…Similar to macroscale motors, an efficiency of NMs is highly important for achieving high speeds and long working time [ 89 ]. Biological nanomotors are very efficient in chemo-mechanical coupling without the need of an intermediate step for chemical-to-electrical-to-mechanical conversion.…”