Reversible Fragmentation and Self‐Assembling of Nematic Liquid Crystal Droplets on Functionalized Pyroelectric Substrates

Merola, Francesco; Grilli, Simonetta; Coppola, Sara; Vespini, Veronica; Nicola, S. De; Maddalena, P.; Carfagna, Cosimo; Ferraro, Pietro

doi:10.1002/adfm.201200323

Cited by 31 publications

(31 citation statements)

References 72 publications

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“…15,[19][20][21][22][23][24][25] Studies have shown that metallic nanoparticle deposition from an aqueous solution onto þZ surfaces of LiNbO 3 domain patterns can be achieved. [23][24][25] The nanopatterned features created using Ag nanoparticles possessed a uniform distribution with a size variation between 2 and 10 nm in both diameter and height.…”

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confidence: 99%

Surface enhanced luminescence and Raman scattering from ferroelectrically defined Ag nanopatterned arrays

et al. 2013

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Surface enhanced luminescence and Raman scattering from ferroelectrically defined Ag nanopatterned arrays

et al. 2013

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“…The pyroelectric field generated by the surface charges in pyroelectric crystals has been recently used for various self-powered micro/nanogenerator or sensors, such as, particle trapping, liquid microlenses, liquid dispensing, wettability patterning, and manipulating LC droplets on the substrate surface [182][183][184][185][186][187]. It has been also demonstrated that the broadband electromagnetic radiations could be converted into heat for generating an appreciable pyroelectric field by depositing a sheet carbon/graphene onto the pyroeletric substrates [188,189].…”

Section: Pyroelectric-hybridised Liquid Crystal Devicesmentioning

confidence: 99%

Self-activating liquid crystal devices for smart laser protection

Wang

2016

Liquid Crystals

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Lasers are now extensively used in a multitude of optical devices and photonic systems spanning from sensing, communication, entertainment, medical surgery to military applications. Direct accidental or intentional exposures to high power lasers may lead to severe temporary or even permanent harm of human eye, skin, or optical sensors. The effective laser protection and shielding are currently not only a subject of scientific research but also a potential public safety issue, therefore there is an urgent need to develop the intelligent laser protection devices for keeping human eyes, optical sensors, and other sensitive components from these unintended or intended damages by laser radiations without warning. Self-activating liquid crystal devices undoubtedly represent such an elegant example because they could be autonomously activated to block or attenuate the lasers when the laser intensity is higher than a maximum permissible exposure value. This review is devoted to summarising the up-to-date significant advances of selfactivating liquid crystal devices for potential smart laser protection, including twist-aligned nematic liquid crystal devices, liquid crystal cored waveguide fibre arrays, and photovoltaic/ pyroelectric-hybridised liquid crystal devices. Finally, the review concludes with the perspectives and challenges for the future development of self-activating liquid crystal devices. It is anticipated that this glimpse and further endeavours in the emerging field will help the researchers from different backgrounds towards the fabrication of highly efficient laser protection devices, their real-world widespread applications and beyond. ARTICLE HISTORY

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“…8 Despite many exciting applications, our actual knowledge of the LN surface atomic structure and the associated surface electric field and surface charge is remarkably limited. LiNbO 3 can be thought of as a stapling of Nb-O 3 -Li trilayers along the [0001] direction (Fig.…”

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“…6 High surface electric fields due to pyroelectricity were found to efficiently pole electro-optic polymers 7 and to lead to the reversible fragmentation and self-assembling of nematic liquid crystals. 8 Despite many exciting applications, our actual knowledge of the LN surface atomic structure and the associated surface electric field and surface charge is remarkably limited. LiNbO 3 can be thought of as a stapling of Nb-O 3 -Li trilayers along the [0001] direction (Fig.…”

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Charge compensation by long-period reconstruction in strongly polar lithium niobate surfaces

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The microscopic structure of the polar (0001) and (0001) surfaces of lithium niobate is investigated by atomic-resolution frequency modulation atomic force microscopy and first-principles calculations. It is found that the surface reconstructs at annealing temperatures sufficiently high to drive off external adsorbates. In particular a ( √ 7 × √ 7)R19.1• reconstruction is found for the (0001) 1 While these applications exploit the peculiar ferroelectric, piezoelectric, photorefractive, and electro-optical properties of the bulk, the strong electric fields and charges at the surfaces of ferroelectric materials have recently attracted the attention of scientists and engineers. For example, it is possible to grow group III nitrides with spatially varied, absolute polarity control on LN substrates.2 The dipole orientation can be switched at the nanoscale, bearing a great potential for domain-specific surface chemistry as a route towards the fabrication of nanoscale devices.3 LN surface charges were found to enable artificial photosynthesis 4 and to drive photocatalytic dye decolorization. 5 The integration of ferroelectric thin films within liquid environments is investigated in the context of laboratory-on-chip device designs, e.g., for localizing, sensing or activating charged biomolecules.6 High surface electric fields due to pyroelectricity were found to efficiently pole electro-optic polymers 7 and to lead to the reversible fragmentation and self-assembling of nematic liquid crystals. 8 Despite many exciting applications, our actual knowledge of the LN surface atomic structure and the associated surface electric field and surface charge is remarkably limited. LiNbO 3 can be thought of as a stapling of Nb-O 3 -Li trilayers along the [0001] direction (Fig. 1). This order gives rise to a spontaneous electric dipole moment and strongly polar (0001) and (0001) surfaces, commonly referred to as negative and positive Z cut, respectively. Using electron diffraction, Yun et al. 9 found no indication for reconstructions on LN(0001) surfaces at ambient conditions. From ion scattering spectroscopy it was concluded that both Z-cut surfaces are oxygen terminated. 9 On the other hand, coaxial impact-collision ion scattering suggested a Nb surface termination.10,11 The experimental investigations are hindered by the extremely challenging preparation and analysis conditions of strongly polar surfaces of insulating materials: Charging effects preclude the application of electron tunneling or diffraction techniques and unscreened surface charges hinder atomic force microscopy. Nonetheless, reconstructions in surfaces commonly referred to as weakly polar surfaces such as the SrTiO 3 (001) and BaTiO 3 (001), have been recently demonstrated by STM 12,13 and transmission electron microscopy 14 techniques. Moreover, the structural and physical properties of polar surfaces are strongly temperature dependent. 15 Only recently, atomic resolution images of the LN(0001) surface have been obtained by frequency modulation atomic force micro...

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Reversible Fragmentation and Self‐Assembling of Nematic Liquid Crystal Droplets on Functionalized Pyroelectric Substrates

Cited by 31 publications

References 72 publications

Surface enhanced luminescence and Raman scattering from ferroelectrically defined Ag nanopatterned arrays

Surface enhanced luminescence and Raman scattering from ferroelectrically defined Ag nanopatterned arrays

Self-activating liquid crystal devices for smart laser protection

Charge compensation by long-period reconstruction in strongly polar lithium niobate surfaces

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