Development of fiber optic liquid crystalline pressure sensor

The paper presents further development of a novel fiber optic low and high hydrostatic pressure sensing technique utilizing new classes of chiral nematic liquid crystals with a significantly reduced thermal sensitivity. The low-pressure sensor is based on polarization effects and employs pressure-induced deformations occurring in a twisted nematic cell. This approach is particularly suitable for measurement of hydrostatic pressure in order of 1 MPa (10 bar) and utilizes strong rotatory power occurring in chiral nematics. In the theoretical part, by using the Berreman 4 X 4-matrix method we present calculations of transmission of a twisted nematic cell. The high pressure sensor is based on intensity phenomena occurring in novel classes of chiral nematics with induced smectic Ad phase and exploits the effect of pressure induced changes in the wavelength of selective Bragg light reflection. The experiment was conducted in a high pressure environment up to 100 MPa (1kbar) and the preliminary data demonstrates a potential of the induced liquid crystal systems for applications in high pressure sensing.