Cholesteric Liquid Crystal Sensing of High Hydrostatic Pressure Utilizing Optical Fibers

A new method of sensing high hydrostatic pressure utilizing cholesteric liquid crystals (ChLCs) as a sensing element and optical fibers for communication with the high-pressure region is proposed and demonstrated the concept exploits the effect of pressure-induced changes in the peak light-reflection wavelength observed in ChLCs. Measurements were performed on an encapsulated ChLC sample obtained by dispersion of a mixture consisting of nematic-host phase with cholesteryl oleyl carbonate and cholesteryl nanoate in a polymer matrix. We used multimode optical fibers for guiding the light to the ChLC sensing element and for transmitting the selectively reflected signal from the cholesteric layers to a detector. The ChLC sample with the optical fibers was placed inside a high-pressure chamber equipped with a fiber-optic leadthrough system, designed to sustain pressure up to 200 MPa. As a result we obtained a set of pressure and temperature characteristics of the device clearly demonstrating its pressure-sensing potential. A brief discussion of the high-pressure and temperature effects in the ChLC sample is also presented in the paper. The construction of a high-pressure sensor based on advanced technology for preparing of ChLCs and exploiting the attractiveness of fiber-optic techniques is proposed.