Fig. 1: Colloidal molecules by purely dielectric spheres of different sizes.
From: Active colloidal molecules assembled via selective and directional bonds
a Schematic illustration of experimental setup for the assembly of colloidal molecules under AC electric field. b Optical microscope image showing the AB colloidal molecules and their propulsion trajectories. Dielectric spheres 1 and 4-µm (diameter, d and D) are used. c Cartoon of an AB colloidal molecule (a side view) and various interparticle forces that account for its formation and dynamics. The larger 4-µm particle is referred to as the central sphere; the smaller 1-µm is referred to as the ligand. d, e Finite-element analysis of the nonuniform electric field locally distributed around a dielectric sphere (D = 4 µm) at AC frequency f = 600 Hz, showing the high-field and low-field region (x–z plane). A negatively polarized particle (e.g., dielectric) experiences negative dielectrophoretic (n-DEP) forces, being attracted towards the low-field region and/or repelled by the high field according to its size. Red arrows represent the direction of electric field lines. Color bar: electric field strength. Scale bar: 4 μm.
