Tunable surface metal morphologies and electrical properties of monodispersed polystyrene beads coated with metal multilayers via electroless deposition

Conducting core–shell beads are composed of a polystyrene (PS) core and a metallic shell of nickel/gold, regardless of their method of preparation. This study examined conducting core–shell beads to identify the metal–polymer interface and the electromechanical response under large deformation. Firstly, monodispersed PS beads, 4.4 μm in diameter, were synthesized by dispersion polymerization. After sequential electroless deposition, the nickel content decreased after gold plating because the nickel deposit oxidized and dissolved into solution while the gold in solution was reduced to the metal on the nickel surface. When the beads were prepared using three different methods, the core–shell beads had a raspberry-like morphology, a smooth surface and an onion-like structure. The electromechanical indentation test of a single conducting core–shell bead (route 1, route 2 and route 3) showed an electrical resistance of 5.0 Ω, 5.1 Ω and 5.8 Ω, respectively. Without a sulfonation process, a noisy response of the electrical signals was observed over the entire range of stain due to the delamination of the metal–polymer interface and mechanical buckling of the metallic layer.