Self‐Propelled Micro/Nanoparticle Motors

Abstract

resulted in a forward motion. Here, the thermodynamic forces act over the inertial thrust. Variations of this motion principle have been reported over the last decade and they will be discussed accordingly in the following sections depending on the micromotor design and the energy source used for its propulsion (i.e., concentration gradient, electric fields, magnetic fields, thermal gradients). Additionally, different approaches to improve the performance in terms of velocity, control, lifetime, and functionality will be covered. However, there are certain constraints on the synthetic autonomous nano-and microparticle performance, such as poor interaction with the surrounding environment (i.e., biological entities) and lack of sensing capabilities, in addition to low lifespan or related toxicity issues. Therefore, biohybrid particulate micromotors appear as a promising solution to overcome such hurdles. They take advantage of the tailored and advanced functions of biological cells or microorganism, such as self-propulsion, sensing, and cargo capabilities, as well as their ability to interact with other cells. Together with the controllability of engineered microobjects, hybrid micro-and nanomotors represent a promising tool for diverse biomedical and environmental applications, where the main power source comes from their natural environment. [11] As shown in Figure 1, in this review we classify micro-and nanoparticle micromotors in two main categories: synthetic and biohybrids. The synthetic micromotors are then divided according to their propulsion mechanism, as follows: those propelled by a catalytic reaction, by optical stimuli, under magnetic fields, with ultrasound steering, electricity, and thermophoresis, respectively. Likewise, the biohybrids are classified as those propelled by bacteria and those employing enzymes as main energy source, respectively. Additionally, we point out the different methods that have been proposed during the last decade to guide the particles and the related collective behavior. We also discuss the potential applications and remaining challenges in the final section of the review. Synthetic Micro/Nanoparticle MotorsThe development of the first sphere-like synthetic micro-and nanomachines with their rotationally symmetric shape was particularly challenging. As per se, they contradict the first rule in the design of microscale devices aiming to perform an effective motility in response to specific energy input: they must present asymmetry. Such symmetry breaking can be associated with shape or the distribution of a certain reactive The growing interest in the design and fabrication of novel autonomous micro-and nanoparticles is motivated by the vast advances in their motion efficiency and their further implementation in both biomedical and environmental fields. The present review covers the motion principle and fabrication procedures of synthetic and hybrid particle-like micromotors reported to date to give a comprehensive view of the key design parameters and different approaches...

Active particles in noninertial frames: How to self-propel on a carousel

“…In the case of vanishing noise ( f (t) = 0, g(t) = 0) the trajectories are deterministic. In the rotating frame, (8) and (9) have the solutions of a circular trajectory with a spinning frequency…”

“…The quantity r (t) − r (0) measures the mean displacement a self-propelled particle has achieved after a time t provided its orientationn (0) has been prescribed at time t = 0. According to the equations (8) and (9), we can use the standard results for a linear swimmer (M = 0) and a circle swimmer. For a linear swimmer [9,42]…”

Theoretical Analysis of Metallic-Nanodimer Thermoplasmonics for Phototactic Nanoswimmers

“…The design and control of nanomotors and molecular machines is a subject of great interest that has undergone enormous development in recent years. Particularly appealing are the so-called "nanoswimmers", suspended nanoparticles (NPs) that navigate through a fluid thanks to mechanical forces that arise from inhomogeneities in their surroundings [1][2][3][4][5][6][7][8] . Such inhomogeneities can be, e.g., gradients of concentration (diffusiophoresis) [9][10][11][12][13][14] or temperature (thermophoresis) [15][16][17][18] .…”

Light‐Driven Sandwich ZnO/TiO2/Pt Janus Micromotors: Schottky Barrier Suppression by Addition of TiO2 Atomic Interface Layers into ZnO/Pt Micromachines Leading to Enhanced Fuel‐Free Propulsion

“…Light‐powered nano/micromotors have recently received great attention of the nano/micromachines communities, since the light energy source can be used simultaneously for motors propulsion and photocatalytic activation to degrade different pollutants in water‐purification applications . Unlike catalytic micromotors, which require destructive/toxic chemical fuels such as H 2 O 2 , the use of light power to activate the motion of these micromachines represents a more environmentally friendly approach that guarantees their potential use in disinfection applications.…”

“…Light-powered nano/micromotors have recently received great attention of the nano/micromachines communities, [1][2][3][4][5][6][7][8][9] since the light energy source can be used simultaneously for motors propulsion and photocatalytic activation to degrade different pollutants in water-purification applications. [10][11][12] Unlike protons (H + ).…”