Exploring the self-assembly behavior of polystyrene microspheres in ripple structures

To overcome the optical diffraction limit, combining micro-sized transparent spheres with photonic nanojet technology is able to achieve nanometer-level high-resolution imaging. To expand the imaging area, it is necessary to create a two-dimensional microsphere array. This paper presents a self-assembly method for fabricating two-dimensional transparent polystyrene microsphere arrays. The method uses radio frequency sputtering to deposit a low-friction graphite coating on the surface of a cured epoxy resin with a rippled structure. The wavelength of this rippled structure is slightly larger than the diameter of the polystyrene microspheres, allowing adjacent polystyrene microspheres in the one-dimensional array to make close contact. The amplitude of the rippled structure effectively prevents the polystyrene microspheres from flipping over. Next, 5 × 10^-6 wt% of polystyrene microspheres are uniformly dispersed in 100 mL of a cosolvent consisting of ethylene glycol and deionized water in an 8:2 weight ratio, and the colloidal solution is heated to 100 °C before being dropped onto the graphite-coated surface with the rippled structure. After the solvent evaporates, a single-layer, ordered arrangement of polystyrene microspheres can form.

Graphical Abstract