Conductive Adhesive Based on Mussel-Inspired Graphene Decoration with Silver Nanoparticles

Abstract

Decoration with silver nanoparticles was obtained by coating graphene with a polydopamine layer, able to induce spontaneous metallic nanoparticles formation without any specific chemical interfacial modifier, neither using complex instrumentation. The choice of dopamine was inspired by the composition of adhesive proteins in mussels, related to their robust attach to solid surfaces. The synthesis procedure started from graphite and involved eco-friendly compounds, such as Vitamin C and glucose as reducing agent and water as reaction medium. Silver decorated graphene was inserted as secondary nanofiller in the formulation of a reference conductive adhesive based on epoxy resin and silver flakes. A wide characterization of the intermediate materials obtained along the step procedure for the adhesive preparation was carried out by several techniques. We have found that the presence of nanofiller yields, in addition to an improvement of the thermal conductivity (up to 7.6 W/m · K), a dramatic enhancement of the electrical conductivity of the adhesive. In particular, starting from 3 · 102 S/cm of the reference adhesive, we obtained a value of 4 · 104 S/cm at a nanofiller concentration of 11.5 wt%. The combined double filler conductivity was evaluated by Zallen's model. The effect of the temperature on the resistivity of the adhesive has been also studied.

Experimental investigation of the adhesion force of single and double‐layer coatings on MEMS surfaces

“…Deposition of layer was carried out in two methods. Single‐layer coatings were the first method, which their effect on reduction of surface adhesion force has been proven in this paper and previous researches . The second method is a double‐layer deposition that is a new method to reduce the surface adhesion force, and the purpose of this method is to change the surface roughness and decrease of adhesion force; this is effective on increasing the efficiency of microassemblies and other equipments of MEMS.…”

“…Therefore, coating materials should have high conductivity and low surface adhesion. Accordingly, many studies have addressed coatings of gold and silver on the silicon substrate …”

“…In the experimental studies, an atomic force microscope (AFM) and a force‐level device (SFA) have been used to obtain the adhesion force. The force measurement with the AFM, due to its high resolution, allows observation and manipulation of molecular and atomic surface features …”

“Green” Synthesis of Nanocarbons for Reduced Friction and Wear

“…The chemically synthesized graphite was then treated by means of a modified Hummers' method [27] in order to oxidize the graphitic planes, hence obtaining graphite oxide (GO). In detail, 1 g of graphite was dispersed in 50 mL of sulfuric acid.…”

“…Among methods allowing mass production of graphene, the chemical strategy [25][26][27][28], of adopting highly pure expensive graphite as the starting material, typically produced through high-energy consumption and intensely polluting processes, is the preferable route. On the other hand, a large amount of agroforestry waste, as well as the increased costs and the still significantly detrimental environmental impact associated with the waste disposal, encourage looking for sustainable conversion of agroforestry waste into useful products [29].…”