Patterning gold nanoparticles in liquid environment with high ionic strength for local fabrication of up to 100 μm...

Metallic interconnections were fabricated in situ using the FluidFM as scanning probe lithography tool. In contrast to other SPL tools, the closed fluidic circuit of the FluidFM enables a pressure-controlled deposition of metallic nanoparticles in liquid environment. Taking advantage of the salt concentration of the liquid environment (i.e. the ionic strength) to tailor the resulting particle density in the deposited layer, a protocol was established for direct patterning of conductive interconnecting structures. The FluidFM microchannel was filled with an aqueous solution of negatively charged gold nanoparticles (AuNPs) to be delivered onto a glass surface coated with a polycation favoring electrostatic adhesion. The deposited structures were analyzed both topographically and electrically to optimize the external parameters such as contact time, salt concentration of the liquid environment and size of the AuNPs. Using this optimized protocol we succeeded in the local fabrication of conductive metallic wires between two prefabricated macroelectrodes in liquid environment. In a subsequent step, the conductivity of the deposited structure was improved by gold annealing.