SENSOR SYSTEM FOR ALCOHOL AND CHLORINATED-HYDROCARBON VAPORS ON THE BASIS OF SEMICONDUCTING POLYMERS

A novel polymer-chemosensor microsystem which can be operated without additional energy consuming heating is presented. Production steps wer e reduced to metal coating of ceramic plates and structuring of an int erdigital array by CAD-supported pulsed laser ablation (PLA) instead o f conventional lithographic techniques which yield low production cost s only for high production numbers. The active sensor film consists of a semiconducting polymer which can be deposited as a polymer precurse r fluid onto the transducer, and can be tempered in-situ to yield the required polymeric species and chemical functionality. A precurser, po ly-2,5-furylene-hydroxy-ethylene, is coated on the pulse-laser process ed interdigital array structures on an Al2O3 substrate and converted t o various poly-2,5-furylene-vinylene (PFV) derivatives by special heat treatments under inert atmosphere, Costly capacitive modulation and l ock-in data acquisition techniques were replaced by simple direct curr ent measurements. Certain sensor types exhibited remarkable sensitivit y e.g. for 1,1,2-trichloroethylene and propanol, but moderate cross se nsitivity for humidity. The response time is of the order of few minut es, and the current signal is linear in a wide analyte pressure range. Sensitivities for alcohols and chlorinated hydrocarbons are most prob ably related to hydrophobic van der Waals interactions whereas Bronste dt acidity or Lewis basicity seem to play minor roles. Electronic or v an der Waals interaction leads to deviation of the idealy flat and rig id structure of the conjugated polymer thus allowing for more flexibil ity of the chains, more intimate inter-chain contacts and higher condu ctivity.