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Mid-wave infrared liquid crystal shutter for breathalyzer applications

Piecek W., Jaroszewicz L., Miszczyk E., Raszewski Z., Mrukiewicz M., Kula P., Jasek K., Perkowski P., Nowinowski-Kruszelnicki E., Zieliński J., Kędzierski J., Olifierczuk M., Chodorow U., Morawiak P., Mazur R., Kowiorski K., Harmata P., Herman J.

Opto-Electronics Review

2017

Vol. 25, No. 2

103--109

There exists a problem with an in situ diagnostics of contamination of ethyl alcohol in a human being exhaled air. When ethyl alcohol in a mouth blowing (in a gaseous state) exists, the characteristic C-H stretch absorption bands in CH3 and CH2 functional groups in ethanol (CH3CH2OH) appear at a wave length of λ = 3.42 µm. To investigate the presence of ethyl alcohol in exhaled human air, the light beam of λ = 3.42 µm is passing through an air sample. If one alternately measures the intensity of the investigated beam and the reference, a percentage of ethanol in the air sample can be estimated using a sensitive nondispersive infrared (NDIR) system with a stable operating flow mass detector. To eliminate a mechanical chopper and noise generating stepper motors, a photonic chopper as a liquid crystal shutter for λ = 3.42 µm has been designed. For this purpose, an innovative infrared nematic liquid crystal mixture was intentionally prepared. The working mixture was obtained by a selective removal of C-H bonds and its exchange by heavier polar substituents, what ensures a lack of absorption band of C-H bonds. The paper presents theory, concept and final experimental results of the infrared nematic liquid crystals mixture and the liquid crystal shutter for breathalyzer applications.