Photoinduced collective motion of oil droplets and concurrent pattern formation in surfactant solution

Tomoya Kojima, Hiroyuki Kitahata, Kouichi Asakura, Taisuke Banno

Research output: Contribution to journalArticlepeer-review


Collective motions are the spontaneous emergence of the ordered movement in living systems. Various constructive approaches have been attempted toward understanding the mechanism. However, few studies have been on the motion induced by biomimetic artificial systems based on molecular conversions. In this study, we report an artificial system of oil droplets in surfactant solutions, wherein collective motion and pattern formation occur concurrently, using the conversion of photoresponsive surfactants. Assembly/dispersion of multiple oil droplets and appearance/disappearance of circular patterns around them occur under UV/visible light illumination, respectively. Moreover, whether the assembled droplets move laterally or not depends on the number of droplets, which is considered analogous to biological organisms in response to population density. These phenomena occur because the photoisomerization of surfactants induces the gradient of interfacial tension, generating specific flow fields around droplets. Our results could be useful for understanding the mechanism of life motion in terms of physicochemical aspects.

Original languageEnglish
Article number101222
JournalCell Reports Physical Science
Issue number1
Publication statusPublished - 2023 Jan 18


  • azobenzene
  • collective motion
  • light
  • oil droplets
  • pattern formation
  • surfactant solution
  • systems chemistry

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • General Engineering
  • General Energy
  • General Physics and Astronomy


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