A Sensing Device Using Liquid Crystal in a Micropillar Array Supporting Structure

Cheng, Daming; Sridharamurthy, S.S.; Hunter, Jacob T.; Park, Joon-Seo; Abbott, Nicholas L.; Jiang, Hongrui

doi:10.1109/jmems.2009.2029977

Cited by 26 publications

(4 citation statements)

References 33 publications

(36 reference statements)

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“…Due to complexation of the salt by 5CB as well as by the analyte gas, the latter forming a much stronger complex than the former, a sensitive and specific response can be ensured. The substrates vary from polystyrene [300] to photolithography masked PDMS and polyurethane microwells [301][302][303]. The team successfully quantified the chemooptical transitions induced upon gas exposure from as low as ppb level concentrations under various humidity settings [300,[302][303][304][305].…”

Section: Gas Sensing With Liquid Crystal-filled Fibersmentioning

confidence: 99%

Liquid crystals in micron-scale droplets, shells and fibers

Urbanski

Reyes

Noh

et al. 2017

J. Phys.: Condens. Matter

171

192

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The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of liquid crystals in spherical and cylindrical geometry, the state of the art of producing such samples, as well as the perspectives for innovative applications that have been put forward.

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Section: Gas Sensing With Liquid Crystal-filled Fibersmentioning

confidence: 99%

Liquid crystals in micron-scale droplets, shells and fibers

Urbanski

Reyes

Noh

et al. 2017

J. Phys.: Condens. Matter

171

192

View full text Add to dashboard Cite

show abstract

“…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. Recently, the group also demonstrated highly sensitive detection of toluene vapour using nematics [32].…”

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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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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“…The authors found that the Mooney-Rivlin model obtained the most accurate FE results for tensile test while the Ogden model obtained the most accurate FE results for compressive test. Cheng et al [16] studied strength of micropillar arrays with liquid crystal thin films between micropillars in Surface Evolver program. The authors found that liquid crystal in the micropillar arrays were robust and resistant to gravitational forces and mechanical shock.…”

Section: Introductionmentioning

confidence: 99%

Compressive Behaviors of Micropillar Sheets Made of PDMS Material Using the Finite Element Method

Pakawan¹,

Puttapitukporn²,

Atthi³

et al. 2020

EngJ

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Thai Microelectronics Center fabricates micropillar sheets from soft lithography techniques and roll-to-roll process which were used as superhydrophobic and superoleophobic surfaces coated on marine structures and medical devices. This research aimed to study appropriate constitutive models and mechanical behaviours of PDMS micropillar sheets with two substrate thicknesses of 1,910 µm and 150 µm under compressive loading using ANSYS Mechanical APDL program. The constitutive models consisted of Mooney-Rivlin (2, 3 and 5 parameters), Ogden (1 st , 2 nd and 3 rd orders), Neo-Hookean, Polynomial (1 st and 2 nd orders), Arruda-Boyce, Gent and Yeoh (1 st , 2 nd and 3 rd orders) models were curved fitting with experiment data from uniaxial compression test. We found that the most accurate constitutive model was Mooney-Rivlin 5 parameter model for the low strain range   ( 0.225) z . The compressive strength and the lateral collapse of micropillars depended on substrate thickness were studied. The lateral collapse of micropillars was found when the substrate thicknesses were 150 µm and 1,910 µm. As the substrate thickness decreased, the compressive strength decreased while the elastic stiffness increased. The maximum compressive forces per one micropillar were 21.060 µN and 18.549 µN for the 1,910 µm and 150 µm thick substrates respectively.

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A Sensing Device Using Liquid Crystal in a Micropillar Array Supporting Structure

Cited by 26 publications

References 33 publications

Liquid crystals in micron-scale droplets, shells and fibers

Liquid crystals in micron-scale droplets, shells and fibers

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

Compressive Behaviors of Micropillar Sheets Made of PDMS Material Using the Finite Element Method

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