Distant mechanical sensors based on cholesteric liquid crystals

Shibaev, Petr; Schlesier, Cristina

doi:10.1063/1.4764525

Cited by 6 publications

(4 citation statements)

References 10 publications

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“…When the temperature was raised to 70 • C, the reflection peak of CLCs disappeared (Figure 8). Formula (2) showed that the optical selective reflection properties of CLCs are related to their helical structures. The helical structures of CLCs altered with the temperature rising from 20 to 50 • C. The reflection wavelength measured by optical fiber reflector was red-shifted by approximately 50 nm.…”

Section: Reflection Spectra Of Clcs In Response To Environmental Tempmentioning

confidence: 99%

“…The helical structure of CLCs is not only related to its material properties but is also a sensitive function of temperature, electromagnetic field, acoustic field, radiation field, and even biochemical sensing. Therefore, CLCs have been widely applied in sensor fields, especially biosensors [1][2][3][4][5][6][7]. The liquid crystalline state has become ubiquitously recognized in organisms, in which the helical structure of amphiphilic lipids from the plasma membrane is a natural composition containing a lyotropic liquid crystal structure.…”

Section: Introductionmentioning

confidence: 99%

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Sensing Characteristics of Side-Polished Fiber Based on the Alterations in Helical Structure of Thermo-Sensitive Cholesteric Liquid Crystals

Han

Jiang

Guo³

2019

Crystals

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Cholesteric liquid crystals (CLCs) are sensitive to environmental temperature changes, and have been employed as a specific intermediary for biosensors. Considering the temperature-dependent structural changes of CLCs, this study aimed to determine the sensing properties of side-polished fibers (SPFs) after coating with CLCs. The experimental results demonstrated that, with regard to the transmitted spectrum, the loss peak of CLC-coated SPFs exhibited a positive linear relationship with temperature changes over a range of 20 to 50 °C. The linear correlation coefficient achieved 97.8% when the temperature increased by 10 °C, and the loss peak drifted by 12.72 nm. The reflectance spectrum of CLCs coated on the polished surface were obtained using optical fiber sensors. The feasibility of measuring the helical structure of CLCs was further verified using SPF transmission spectroscopy. The findings indicated that the transmitted spectrum of SPFs could be adopted to characterize the helical structure of CLCs, which lays a solid foundation for further study on SPF-based biosensors.

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Section: Reflection Spectra Of Clcs In Response To Environmental Tempmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sensing Characteristics of Side-Polished Fiber Based on the Alterations in Helical Structure of Thermo-Sensitive Cholesteric Liquid Crystals

Han

Jiang

Guo³

2019

Crystals

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“…The periodic helical structure of the CLC cell can be changed by various external stimuli such as heat, electric fields or magnetic fields [ 7 , 8 , 9 ]. Due to these characteristics, CLCs have been studied regarding the fabrication of optical devices for various applications such as liquid crystal displays (LCDs), dye lasers, notch filters, optical sensors and mirrors [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. However, when the CLC cell is inclined with respect to the incident beam the reflection band shifts to a shorter wavelength due to the Bragg condition and a higher order reflection band appears [ 12 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

Characterization of Second-Order Reflection Bands from a Cholesteric Liquid Crystal Cell Based on a Wavelength-Swept Laser

Ahn

Kim

et al. 2020

Sensors

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We report the results of an experimental study of the characterization of second-order reflection bands from a cholesteric liquid crystal (CLC) cell that depends on the applied electric field, using a wide bandwidth wavelength-swept laser. The second-order reflection bands around 1300 nm and 1500 nm were observed using an optical spectrum analyzer when an electric field was applied to a horizontally oriented electrode cell with a pitch of 1.77 μm. A second-order reflection spectrum began to appear when the intensity of the electric field was 1.03 Vrms/μm with the angle of incidence to the CLC cell fixed at 36°. The reflectance increased as the intensity of the electric field increased at an angle of incidence of 20°, whereas at an incident angle of 36°, when an electric field of a predetermined value or more was applied to the CLC cell, it was confirmed that deformation was completely formed in the liquid crystal and the reflectance was saturated to a constant level. As the intensity of the electric field increased further, the reflection band shifted to a longer wavelength and discontinuous wavelength shift due to the pitch jump was observed rather than a continuous wavelength increase. In addition, the reflection band changed when the angle of incidence on the CLC cell was changed. As the angle of incidence gradually increased, the center wavelength of the reflection band moved towards shorter wavelengths. In the future, we intend to develop a device for optical wavelength filters based on side-polished optical fibers. This is expected to have a potential application as a wavelength notch filter or a bandpass filter.

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“…Also, colour changes were observed in non-crosslinked, high viscosity CLC films upon straining. 15,16 However in these systems, the reflection band tends to revert back to its initial position over time when the film is in the deformed state and, consequently, these films are not true strain sensors. We have previously shown that a well defined CLC organisation can be obtained by spray-coating a solution of CLC monomers on oriented polymer tapes and fibres.…”

Section: Introductionmentioning

confidence: 99%

A real time optical strain sensor based on a cholesteric liquid crystal network

et al. 2013

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A flexible, strain sensor for monitoring uniaxial deformations in oriented polymer films is demonstrated. The sensor consists of a crosslinked cholesteric liquid crystal layer which is spray-coated on a uniaxially oriented polyamide 6 substrate. When no deformation is applied, reflectivity measurements showed a well-defined reflection band. Upon uniaxial extension, the reflection band shifted towards lower wavelengths. A 40 nm shift was recorded for 13% of strain. This wavelength shift is attributed to a decrease in the cholesteric helix's pitch which is induced by the change in thickness of the CLC coating due to Poisson's contraction. As a result the colour of the film changed from orange to green with increasing strain. The optical response was found to follow the mechanical behaviour of the polymer substrate. Cycling loading showed a time dependent optical response of the sensor fitting with the viscoplastic mechanical response of the substrate giving real time information on the deformation.

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Distant mechanical sensors based on cholesteric liquid crystals

Cited by 6 publications

References 10 publications

Sensing Characteristics of Side-Polished Fiber Based on the Alterations in Helical Structure of Thermo-Sensitive Cholesteric Liquid Crystals

Sensing Characteristics of Side-Polished Fiber Based on the Alterations in Helical Structure of Thermo-Sensitive Cholesteric Liquid Crystals

Characterization of Second-Order Reflection Bands from a Cholesteric Liquid Crystal Cell Based on a Wavelength-Swept Laser

A real time optical strain sensor based on a cholesteric liquid crystal network

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