Quantum mechanics

Phototaxis

Chemical physics

Ecology

Biology

Flock

Photochemistry

Materials science

Control reconfiguration

Embedded system

Molecule

Computer science

Botany

Swarm behaviour

Anthropology

Polymer

Collective behavior

Physics

Nanotechnology

Sociology

Artificial intelligence

Azobenzene

Flocking (texture)

Composite material

Astrobiology

Chemistry

Collective motion

Biological system

Biophysics

iScience

Inspired by astonishing collective motions and tactic behaviors in nature, here we show phototactic flocking of synthetic photochemical micromotors. When enriched with hydroxyl groups, TiO2 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.

Phototactic Flocking of Photochemical Micromotors