Figure 1.

Characterization and Spontaneous Clustering Behaviors of the Micromotors

(A) Scanning electron microscopy (SEM) image, X-ray diffraction (XRD) pattern, and TG-DSC analysis of the TiO₂ micromotors. Scale bar: 200 nm.

(B) TiO₂ micromotor flocks in the aqueous medium with 0.25 wt.% H₂O₂. Scale bar: 20 μm.

(C) Numerical simulation of electric potential (ϕ) resulting from the different diffusivities of the secreted H⁺ and OH⁻ around three TiO₂ micromotors with an interparticle distance of 3 μm. Black triangles indicate the direction of E.

(D) The simulated velocity in the X direction (u) and streamlines (black curves) of the converging hydrodynamic flow induced by the electroosmotic slip of electron double layer of the glass substrate and TiO₂ micromotors under the local E, indicating that TiO₂ micromotor 1 and 3 would move toward 2 along the converging electroosmotic fluid flow.

(E) Clustering behaviors of the micromotors with different C_OH obtained at different temperatures, and those obtained at 650°C after alkaline hydrogen peroxide (AHP) treatment, respectively.

Scale bar: 20 μm.