The contactless smart card. The card dimensions are 8 cm × 5 cm with integral antenna, radio-frequency identification (RFID) processor, signal processing electronics and conductometric sensor interface. (II) Conductometric transducers fabricated from planar gold electrodes on FR4 glass fibre substrates (diameter 25 mm). Transducers were coated with thin-films of PEDOT-PSS by spin-coating. Four different electrode geometries were used, (a) T-type, (b) P-type, (c) Q-type and (d) D-type.