Phototactic Flocking of Photochemical Micromotors

Fangzhi Mou; Jianhua Zhang; Zhen Wu; Sinan Du; Zexin Zhang; Leilei Xu; Jianguo Guan

doi:10.1016/j.isci.2019.07.050

Phototactic Flocking of Photochemical Micromotors

iScience. 2019 Sep 27:19:415-424. doi: 10.1016/j.isci.2019.07.050. Epub 2019 Aug 2.

Authors

Fangzhi Mou¹, Jianhua Zhang¹, Zhen Wu¹, Sinan Du², Zexin Zhang³, Leilei Xu¹, Jianguo Guan⁴

Affiliations

¹ State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, 122 Luoshi Road, Wuhan 430070, China.
² State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
³ State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China. Electronic address: zhangzx@suda.edu.cn.
⁴ State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, 122 Luoshi Road, Wuhan 430070, China. Electronic address: guanjg@whut.edu.cn.

Abstract

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.

Keywords: Catalysis; Chemistry; Nanoparticles.