Optical detection of organic vapors using cholesteric liquid crystals

Chang, Chin-Kai; Kuo, Hui-Lung; Tang, Kea-Tiong; Chiu, Shih-Wen

doi:10.1063/1.3627162

Cited by 60 publications

(41 citation statements)

References 12 publications

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“…We are currently experiencing an increasing interest in gas sensors based on liquid crystals (LCs) [32][33][34][35][36][37][38][39][40][41], functioning at room temperature, requiring no energy supply as they are powered by thermal energy alone, and delivering a strong optical response that is easily detected without complex spectroscopic equipment. The response is due to the ability of certain gas molecules, even at low concentration, to strongly influence the liquid crystal self-assembly [40,[42][43][44][45], triggering a reorientation of the liquid crystal director [32,34,43,44], a change in period of the supramolecular helix of shortpitch cholesterics [19,36,42,[46][47][48], or even complete loss of long-range ordering [11].…”

Section: Introductionmentioning

confidence: 99%

“…The response is due to the ability of certain gas molecules, even at low concentration, to strongly influence the liquid crystal self-assembly [40,[42][43][44][45], triggering a reorientation of the liquid crystal director [32,34,43,44], a change in period of the supramolecular helix of shortpitch cholesterics [19,36,42,[46][47][48], or even complete loss of long-range ordering [11]. In particular, Abbott and his group [35,39,[43][44][45] demonstrated the capability of nematic LCs as sensors for detecting nerve agents at concentrations as low as part per billion.…”

Section: Introductionmentioning

confidence: 99%

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Non-electronic gas sensors from electrospun mats of liquid crystal core fibres for detecting volatile organic compounds at room temperature

Sharma

Lagerwall

2016

Liquid Crystals

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Non-woven mats comprised of liquid crystal-functionalised fibres are coaxially electrospun to create soft gas sensors that function non-electronically, thus requiring no power supply, detecting organic vapours at room temperature. The fibres consist of a poly(vinylpyrrolidone) (PVP) sheath surrounding a core of nematic 4-cyano-4ʹpentylbiphenyl (5CB) liquid crystal. Several types of mats, containing uniformly cylindrical or irregular beaded fibres, in uniform or random orientations, are exposed to toluene vapour as a representative volatile organic compound. Between crossed polarisers all mats respond with a fast (response time on the order of a second or faster) reduction in brightness during gas exposure, and they return to the original state upon removal of the gas almost as quickly. With beaded fibres, the response of the mats is visible even without polarisers. We discuss how variations in fibre spinning conditions such as humidity level and the ratio of core-sheath fluid flow rates can be used to tune fibre morphology and thereby the response. Considering future development perspectives, we argue that fibres turned responsive through the incorporation of a liquid crystal core show promise as a new generation of sensors with textile form factor, ideal for wearable technology applications. ARTICLE HISTORY

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Non-electronic gas sensors from electrospun mats of liquid crystal core fibres for detecting volatile organic compounds at room temperature

Sharma

Lagerwall

2016

Liquid Crystals

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“…We define shift from original wavelength to shorter wavelength as "blue-shift" and longer wavelength as "red-shift". The primary composition of nematic LCs consisted of (1) Shiff-bases (azomethine), (2) Demus esters, (3) tolans (diphenylacetylene), (4,5) phenylcyclohexyls, (6) biphenyls, and (7) bicyclohexanes. We named them LC (1) to (7) and their primary molecular structures are shown in Table 1.…”

Section: Experimental 21 Materialsmentioning

confidence: 99%

“…Recently, studies have shown that cholesteric liquid crystals (CLCs) have great potential to be gas sensors for pathology examination and hazardous gases detection [3,4]. It is well known that the peak wavelength of selective reflection (O max ) of CLCs changes upon interaction with an adsorbed gas [5].…”

Section: Introductionmentioning

confidence: 99%

75-3: Chemical Gas Sensors using Chiral Nematic Liquid Crystals

Otono

Kek²,

Lee³

et al. 2016

SID Symposium Digest of Technical Papers

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“…Recent studies have shown that cholesteric liquid crystals (CLCs) have great potential to be used as gas or environmental sensors . The peak wavelength of selective reflection (λ max ) of CLCs changes upon interaction with an adsorbed gas …”

Section: Introductionmentioning

confidence: 99%

Chemical gas sensors using chiral nematic liquid crystals and its applications

Kek¹,

Lee²,

Otono

et al. 2017

J Soc Info Display

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This paper clarifies the relationship between the molecular structures of chiral nematic liquid crystals and the shift in their reflection spectrum resulting from contact with volatile organic compounds (VOCs). We also propose a mechanism to explain the red‐ or blue‐shift in the peak wavelength upon contact with VOC vapor. Furthermore, enhancement of the sensitivity of this method of VOC detection is discussed.

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Optical detection of organic vapors using cholesteric liquid crystals

Cited by 60 publications

References 12 publications

Non-electronic gas sensors from electrospun mats of liquid crystal core fibres for detecting volatile organic compounds at room temperature

Non-electronic gas sensors from electrospun mats of liquid crystal core fibres for detecting volatile organic compounds at room temperature

75-3: Chemical Gas Sensors using Chiral Nematic Liquid Crystals

Chemical gas sensors using chiral nematic liquid crystals and its applications

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