Microfluidic plasmon sensors prepared by dewetting of metal films during hot-embossing of glass

A method for the preparation of a microfluidic plasmon sensor is proposed. Soda-lime-silica float glass was coated with a 20 nm silica layer and subsequently with a 12 nm gold film. Then this layers were covered with a further 20 nm silica layer. This substrate was structured with microfluidic cavities by isothermal hot-embossing at 660 °C, where the coatings effectively prevented the sticking of the glass on the mould. During the forming process, the formation of gold nanoparticles with a size of 20-150 nm occurs. In a second step, the micro structured substrate was bonded to another equally coated, but unstructured, substrate by annealing at 600 °C for 1 h. The transmission spectra of the resulting microfluidic chip show a local plasmon resonance peak at 551,9 nm (in air). The plasmon resonance responds very sensitive to the refractive index of a surrounded liquid (0,5 nm for Än = 0.04), in spite of the covering with a silica layer and the embossing process. For comparison, two simple cuvettes also coated with gold nanoparticles but one with and one without the silica cover layer, both without the hot embossing procedure were prepared. They were filled with the same liquids and transmission spectra were recorded; they show a slightly higher sensitivity. Furthermore, a theoretical model which reflects the measured performance is proposed.