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Phototropic Aggregation and Light-Guided Long-Distance Collective Transport of Colloidal Particles
journal contribution
posted on 2020-06-11, 21:05 authored by Xiaoran Wu, Xiang Xue, Jinghang Wang, Hewen LiuPhoretic
swarming and collective transport of colloidal particles
in response to environmental stimuli have attracted tremendous interest
in a variety of fields. In this work, we investigate the light-actuated
motion, aggregation, and light-guided long-distance mass transport
of silica microspheres in simple spiropyran solutions under the illumination
of UV spot sources. The phototactic motion is confirmed by the dependence
of swarming on the illumination intensity and spiropyran concentrations,
ON–OFF switching tests, pattern-masked UV sources, etc. The
aggregates formed via swarming of silica spheres can chase after a
moving UV source, however, relying on a critical speed of the UV source.
Only when the UV source speed is below the critical value, the aggregates
follow the UV spot at a constant relative speed to the light spot.
Analysis on the shape of silica microsphere currents indicates that
continuous illumination of the UV spot source and resultant chemical
gradients are important for the formation of steady microsphere currents.
Light-guided aggregation and long-distance mass transport are interesting
for targeted delivery and remote-controlled enrichment of environmental
hazards.