Fabrication of interconnected silver flakes for conductive adhesives through dopamine-induced surface functionalization

There is an increasing interest in developing interlocking network fillers for preparation of highly conductive adhesives at low sintering temperature. In this paper, we presented a new approach for preparation of interconnected micrometer-sized silver flake fillers, enabling the wide use of high conductive and flexible adhesives. The approach involves (i) decoration of a nanometer thin layer of poly(dopamine), an excellent catecholic functionalized adhesive protein, on the silver flake surface, which acted as the chemi-sorption sites of silver ions and enabled the reduced silver nanoparticles deposition; (ii) one-step reduction and fixation of silver nanoparticles on the surfaces of poly(dopamine) coated silver flakes, which made the preferred uniform dispersion of nanoparticles in the silver flake filled adhesives. The results indicated that a dense layer of silver nanoparticles with an average diameter less than 50 nm completely covered the silver flake surfaces, and the morphology studies showed the interconnection generated among flakes by sintering of silver nanoparticles. Furthermore, the electrical measurements suggested that both the coverage density of nanoparticles on the flake surfaces and the thickness of the coated poly(dopamine) layer played a role in the silver nanoparticles sintering, and hence of the electrical resistivity of the resultant adhesives.