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.