PRINTED MICROELECTRODE ARRAY AND AMPEROMETRIC SENSOR FOR ENVIRONMENTAL MONITORING

A disposable electrochemical sensor for the determination of heavy met al traces has been designed for environmental field analysis. The sens or is supported on a polycarbonate film and consists of an amperometri c transducer in combination with an adjacent silver-ink reference elec trode. The transducer itself is composed of a network of carbon disc m icroelectrodes. This array of microelectrodes covers a sensing area of 5 x 5 mm and is made up of some 1000-3000 electrodes. Individual disc microelectrodes measuring 15 mu m diameter, have a recessed geometry with hole depth of less than 10 mu m and centre-to-centre separation b etween 100 and 300 mu m. A novel three-stage fabrication process based on conventional thick-film printing techniques, vacuum polymerisation of a dielectric and a uv excimer laser photoablation process was used to pattern the disc array structure. This microfabrication method has been evaluated on a laboratory scale and batch production. Amperometr ic performance and structural characteristics of the electrochemical s ensor have been examined by chronoamperometry and electron microscopy. Variations in the sensor current response were studied in order to re duce the diffusion shielding characteristics of individual discs. An o ptimal microelectrode spacing was assigned to the sensor of 160 mu m g iving more than one thousand discs per device. The printed sensor is c urrently under development for single-use field measurements of heavy metals using potentiometric stripping analysis.