Optical humidity sensor with a fast response time using dye-adsorbed Langmuir-Blodgett films

When Langmuir-Blodgett (LB) films made of multilayered stearic acid or hematoporphyrin containing a phenol-red dye were exposed to a moist environment, changes in the absorption coefficient occurred. This is due to an ionization reaction of the dye molecules dispersed into these LB films. The optical humidity sensors which were simply constructed using these dye-adsorbed LB films operated with good reproducibility and a very fast response time.