TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Device: In the sensing device, the ionic dye is released in response to chemical or electrochemical reduction of the intrinsically conducting polymer; and the polymer forms all or part of a cathode of an electrochemical cell.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The substrate is selected from paper, plastic, wood, glass, ceramic, fabric, metal, and metal oxides. The chemical oxidant is selected from metal salt of sulfonates, sulfates, chlorides, perchlorates and phosphates.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The polymerization retardant is pyridine. The ionic dye is a triarylmethane dye (preferably sulfonphthalein dye, especially at least one of phenol red, xylene cyanol FF, thymol blue, m-cresol purple and cresol red). The monomers to be polymerized are selected from optionally substituted aromatic compounds (preferably optionally substituted 5-membered aromatic heterocyclic compounds, especially at least one of optionally substituted pyrrole, optionally substituted thiophene, optionally substituted aniline, optionally substituted furan, optionally substituted pyridine, optionally substituted indole, and optionally substituted carbazole).    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: In the method (M2), the mixture is printed onto the surface of the substrate by at least one technique selected from spraying, screen printing, flexographic printing, and inkjet printing. EXAMPLE - Tissue paper was first coated with a conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT). This was achieved by applying an oxidant solution of iron(III)para-toluenesulfonate (40%) in butan-1-ol, drying it on a hotplate at 70 degrees C for 5 minutes and then exposing the coated substrate to 3,4-ethylenedioxythiophene monomer vapor. The latter step was carried out in a glass vessel with a small amount of the liquid monomer in the bottom which was maintained in equilibrium with the atmosphere in the vessel by magnetically stirring. After 20 minutes at room temperature, the paper substrate was fully coated with PEDOT and it was withdrawn from the treatment chamber and any unreacted monomer evaporated. The PEDOT-coated paper was then washed in water and air dried. The sodium salt of phenol red (50 mg) was dissolved in a 50:50 mixture (wt/wt) of water:ethanol (2 mL). This solution was then added to an aliquot of the iron(III)para-toluenesulfonate oxidant solution specified previously (3.25 mL) and pyridine (0.15 mL) and applied to the PEDOT-coated tissue paper. Vapor phase polymerization of polypyrrole was then performed, with the exception that pyrrole was used as the monomer. After polymerization, the polypyrrole was washed three times in deionized water for 10 minutes in order to remove reaction products and excess chemicals. The coated tissue paper sample was used as the cathode in a galvanic cell, with a strip of zinc metal as the anode. The electrolyte used was 10 mL of 0.1 M NaCl. Upon completion of the galvanic circuit, phenol red dye molecules were released into the electrolyte solution.