Development of a piezo-optical chemical monitoring system

The development of an environmental and occupational chemical monitoring system based on a piezoelectric polymer film badge is described. Colour changes in reagent spots on the polymer film are measured by illumination with a flashing LED. Non-radiative decay of the excited states produced by optical absorption leads to heat and thermal expansion which stresses the polymer, generating a charge which is measured using a lock-in amplifier. The principles and the optimisation of materials and measuring system are described with reference to the development of an ammonia monitoring system.