Albumin/gelatin gel (AG) properties are studied with an innovative cold‐plasma‐treatment‐based technique. Gel films are produced in situ on polyethylene terephthalate (PET) plates previously treated by gas (O2, air and Ar) cold plasma. After detaching the films from the surface, the contact angles of probe liquids are measured and wettability studied, based upon the induced changes of AG surface free energy. The effect of gelatin concentration in the AG is analysed. Oxygen‐cold‐plasma‐treated PET plates induce outstanding changes in wetting properties. Optical profilometry is used for the characterisation of surface topography. Dynamic oscillatory measurements help check for mesoscopic changes. The latter technique allows shaping of gel sample stiffness. The findings support a new methodology for biomaterials/biopolymer activation when unable to be exposed to the plasma working conditions.