Therefore, an interface can used. In order to obtain this immobilization, a monolayer of symmetrical particles is usually adsorbed onto a flat solid surface and, subsequently, its outer upper part is modified . In this way, Janus particles come from symmetrical particles. For desymetrization, chemical or physicochemical processes are used. Among these processes, we can highlight (i) top-selective modification, (ii) selfassembly by templates, (iii) controlled phase separation phenomena and (iv) controlled surface nucleation. Among the various synthesis strategies, self-assembly, masking and phase separation stand out .