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. 2019 Aug 2;19:415–424. doi: 10.1016/j.isci.2019.07.050

Figure 2.

Figure 2

Phototactic Flocking of the Micromotors

(A) Phototactic and Brownian motions of single TiO2 micromotors when UVY is on and off, respectively. Images are taken from Video S2. Scale bar: 10 μm.

(B) Optical microscopic images (Top panels) and trajectories (Bottom panels) of the TiO2 micromotors in a flock under UVY irradiation. Scale bar: 20 μm.

(C) Optical microscopic images (Top panels) and trajectories (Bottom panels) of the TiO2 micromotors in a flock when UVY is turned off. Images in B and C are taken from Video S3. Scale bar: 20 μm.

(D) Instantaneous velocity vectors of the TiO2 micromotors in a flock when UVY is on. The length and the color of the arrows denote the magnitude of the velocity, with red and long arrows being the fastest, and dark and short arrows being the slowest. Scale bar: 20 μm.

(E) Steady-state distribution of O2 concentration (C) around three TiO2 micromotors with an interparticle distance of 2 μm. Black triangles represent the gradient (∇C) of O2 concentration. Purple arrows and curves represent the direction of incident UV light and the illuminated surfaces of the micromotors, respectively.

(F) Simulated velocity in the X direction (u) and streamlines (black curves) of the hydrodynamic flow induced by ∇C along the surface of the micromotors.