Engineering on chip nanoporous gold material libraries via precision photothermal treatment.
Libraries of nanostructured materials on a single chip are a promising platform for high throughput and combinatorial studies of structure property relationships in the fields of physics and biology. Nanoporous gold (np Au) produced by an alloy corrosion process, is a nanostructured material specifically suited for such studies because of its self similar thermally induced coarsening behavior. However, traditional heat application techniques for the modification of np Au are bulk processes that cannot be used to generate a library of different pore sizes on a single chip. Here, laser micro processing offers an attractive solution to this problem by providing a means to apply energy with high spatial and temporal resolution. In the present study we use finite element multiphysics simulations to predict the effects of laser mode (continuous wave vs. pulsed) and thermal conductivity of the supporting substrate on the local np Au film temperatures during photothermal annealing. Based on these results we discuss the mechanisms by which the np Au network is coarsened. Thermal transport simulations predict that continuous wave mode laser irradiation of np Au thin films on a silicon substrate supports the widest range of morphologies that can be created through photothermal annealing of np Au. Using the guidance provided by simulations, we successfully fabricate an on chip material library consisting of 81 np Au samples of 9 different morphologies for use in the parallel study of structure property relationships.
Nanoscale