Dual Emulsion Fabrication Approach to Core–Shell Microspheres for Polymer Laser Direct Writing

A unique BaTiO3@PS core–shell microsphere responsive to a near-infrared (NIR) laser is designed and successfully prepared using a dual water-in-oil-in-water emulsion method. The BaTiO3 powder was precisely encapsulated in the PS resin in a uniformly dispersed state, with an average particle size of 10.8 μm. The core material, BaTiO3 powder, has a high photothermal conversion efficiency. It cooperates with the external easily carbonized PS to effectively improve the performance of the polymer NIR laser direct writing (LDW). SEM and EDS results confirm the successful preparation of regular microspheres. Raman tests and XPS analysis indicate that the mechanism of black pattern formation of the polymer under the NIR laser is attributed to the generation of amorphous carbon during the LDW process. These core–shell structured microspheres have expanded the application scope of polymer LDW, rendering it more practically valuable. Additionally, this dual emulsion approach has introduced new concepts for designing and fabricating color-changing microspheres.