Phototactic Flocking of Photochemical Micromotors

Abstract

Summary Inspired by astonishing collective motions and tactic behaviors in nature, here we show phototactic flocking of synthetic photochemical micromotors. When enriched with hydroxyl groups, TiO 2 micromotors can spontaneously gather into flocks in aqueous media through electrolyte diffusiophoresis. Under light irradiation, due to the dominant nonelectrolyte diffusiophoretic interaction resulting from the overlap of asymmetric nonelectrolyte clouds around adjacent individuals, these flocks exhibit intriguing collective behaviors, such as dilatational negative phototaxis, high collective velocity, and adaptive group reconfiguration. Consequently, the micromotor flocks can migrate along pre-designed paths and actively bypass obstacles with reversible dilatation (expansion/contraction) under pulsed light navigation. Furthermore, owing to the enhanced driving force and rapid dilatational area covering, they are able to execute cooperative tasks that single micromotors cannot achieve, such as cooperative large-cargo transport and collective microenvironment mapping. Our discovery would promote the creation of reconfigurable microrobots, active materials, and intelligent synthetic systems.

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

“…For example, the collective behavior of an active Ag/AgCl micromotor and passive PS bead system was illustrated by Wang et al [64], showing that the Ag/AgCl micromotors exclude the surrounding PS beads under visible-light irradiation, as shown in Figure 10(a). Similar collective behaviors of micro/nanomotors have been reported in the literature [60,116], as shown in Figures 10(b) and 10(c), respectively.…”

Recent Advances in Nano‐ and Micromotors

“…This strategy was also successful for SiO 2 /Pt, TiO 2 , ZnO and E. coli particles, thus showing a versatile route for precise temporal‐spatial control and manipulation of numerous micromotors. Analogously, clustering of individual TiO 2 micromotors into a swarm was achieved by switching on and off the UV light source . The surface chemistry of the micromotors was modified due to the presence of OH − ions in solution, resulting in particle interaction to form a flock of particles once the light source was off.…”

“…Analogously, clustering of individual TiO 2 micromotors into a swarm was achieved by switching on and off the UV light source. [50] The surface chemistry of the micromotors was modified due to the presence of OH − ions in solution, resulting in particle interaction to form a flock of particles once the light source was off. Upon irradiation with UV light, the micromotors separated and moved as individual motors with an average velocity of 4.6 µm s −1 .…”

Self-Propelled Janus Microdimer Swimmers under a Rotating Magnetic Field

“…Micro-/nanoswimmers that can convert various types of energy into kinetic energy overcoming viscous drag forces and thermal fluctuations have demonstrated different tasks in various environments [1][2][3][4][5][6][7][8][9]. Recent strides in nanotechnology have enabled researchers to develop micro-and nanorobot systems to perform great potential in the fields of drug delivery [10][11][12][13][14][15], biosensing [16,17], self-assembly [18][19][20], micro-manipulation [21][22][23], environmental detection and remediation [24][25][26][27][28] and super-resolution optical imaging [29,30].…”