Nano/Micromotors in Active Matter

Abstract

Nano/micromotors (NMMs) are tiny objects capable of converting energy into mechanical motion. Recently, a wealth of active matter including synthetic colloids, cytoskeletons, bacteria, and cells have been used to construct NMMs. The self-sustained motion of active matter drives NMMs out of equilibrium, giving rise to rich dynamics and patterns. Alongside the spontaneous dynamics, external stimuli such as geometric confinements, light, magnetic field, and chemical potential are also harnessed to control the movements of NMMs, yielding new application paradigms of active matter. Here, we review the recent advances, both experimental and theoretical, in exploring biological NMMs. The unique dynamical features of collective NMMs are focused on, along with some possible applications of these intriguing systems.

Colloids in two-dimensional active nematics: conformal cogs and controllable spontaneous rotation

“…Our work paves the way to using colloids to induce desired dynamical responses in active nematics, including as work-extracting micromachines [33,34]. A natural continuation would be to complement the far-field results presented here with a theoretical understanding of how the motion of active nematic defects is rectified by colloidal surfaces [53,72], as this is key to using inclusions to temper active nematic turbulence [7,73] and may more closely represent the experimental conditions of [53].…”

“…The lower limit of integration is left unspecified as it only provides a constant that may be absorbed into A. The proof that (34) truly is an analytic function as required is based upon showing that…”

“…An ongoing challenge across all forms of active matter is to devise means of rectifying the non-equilibrium dynamics of active systems, allowing for the extraction of useful work and the development of active micromachines [33,34]. Such a harnessing of active dynamics is strikingly typified by bacterial ratchets [35,36]-the spontaneous and persistent rotation of chiral cogs immersed in a bath of bacteria, a phenomenon that is precluded in equilibrium systems.…”

Magnetic micromotors crossing lipid membranes

“…[1][2][3][4][5] From the first examples in simple, aqueous environments, efforts have evolved towards more complex media (i.e., gels, cellulose, cell media) and eventual in vitro and in vivo experimentations, as reviewed in detail. [6][7][8][9][10][11] In contrast, the motion of motors in patterned or confined environments 12 and controlling motor swarming [13][14][15] are still ongoing endeavors.…”

“…, gels, cellulose, cell media) and eventual in vitro and in vivo experimentations, as reviewed in detail. 6–11 In contrast, the motion of motors in patterned or confined environments 12 and controlling motor swarming 13–15 are still ongoing endeavors.…”