Thin layer copper ISE for fluidic microsystem

A miniaturised ion-selective electrode (ISE) for Cu2+ ions was developed, specially designed for application in a fluidic microsystem. The electrode was prepared on a silicon wafer substrate coated with a Cu deposit in the thickness range of 50–200 nm. The Cu layer was quantitatively converted into CuS by treatment in a sulphidic ambient. The chip electrode has a size of 5 mm×5 mm and was mounted on a spacer chip coupled to the fluidic microcell using a chip-clip technology. The coupling is liquid proof and reversible, permitting an easy exchange of the chip electrodes. The effective electrode area contacting the liquid of the microsystem flow channel amounts to about 4 mm2. ivity measurements were performed stationary and in the flow through cell. A good Nernstian response of 29 mV/pCu between pCu 5 and 1 was found, agreeing very well with reference measurements carried out with a commercial ISE. pid response observed even in the dilutest solutions used, is related to the thin, non-porous structure of the CuS layer, minimising diffusion effects during changing the test solutions. The adhesion of the sensitive CuS layer is different for the substrates Si, SiO2 and Si3N4 and depends on their history, roughness and evaporation conditions.