Electric-field sensor prepared using nematic liquid-crystal droplet materials and optical fiber systems

Hai-Guang Zhou; Min Han

doi:10.1117/12.456074

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14 February 2002 Electric-field sensor prepared using nematic liquid-crystal droplet materials and optical fiber systems

Hai-Guang Zhou, Min Han

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Proceedings Volume 4578, Fiber Optic Sensor Technology and Applications 2001; (2002) https://doi.org/10.1117/12.456074
Event: Environmental and Industrial Sensing, 2001, Boston, MA, United States

Abstract

This paper present a further development of electric field sensor and pressure sensor. They use new liquid crystal droplet materials. We discuss some of the features of devices formed from these materials. First of all, this material is a flexible plastic sheet, which can be readily polymerized to any thickness, size, or form. Devices formed from this material do not require sealing and can be fabricated as large, flexible plastic sheets that can be cut or trimmed. The principle of operation of sensors formed from thin films of this material is to regulate the light scattering properties of droplets of the birefringent liquid crystal by applications of an electric field. The electric field is which the material is sandwiched between glass or plastic sheets containing transparent conducting electrodes. In the absence of a voltage to the electrodes (off state), the optic axes of the microdroplets are randomly oriented as illustrated and scatter light. In this state the material appears an opaque white. Upon removal of the applied voltage, the large surface-area-to-volume ratio of the microdroplets allows surface interactions to return the nematic material to its random alignment and opaque texture. An electric field sensor is prepared using nematic liquid- crystal droplet materials and optical fiber systems. Transmission light intensity through the droplets is modulated by an ac electric field and its amplitude increases in good proportion to the electric field strength, covering a wide range. This paper presents a further development of a new fiber optic ion and high hydrostatic pressure sensing technique utilizing new classes of nematic liquid crystals droplets with a significantly reduced thermal sensitivity. The low- pressure sensor (up to 0.7 MPa) is based on polarization effects caused by strong rotary power of chiral nematics and pressure-induced deformations of a twisted nematic cell. The high-pressure sensor (up to 70 MPa) is based on intensity phenomena occurring in novel classes of chiral nematics with induced smectic phase. The latest results indicate that our method of hydrostatic pressure measurement offers high response to pressure with reduced temperature sensitivity.

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Hai-Guang Zhou and Min Han "Electric-field sensor prepared using nematic liquid-crystal droplet materials and optical fiber systems", Proc. SPIE 4578, Fiber Optic Sensor Technology and Applications 2001, (14 February 2002); https://doi.org/10.1117/12.456074

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