Anatoliy Glushchenko

University of Colorado Colorado Springs, Colorado Springs, Colorado, United States

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Publications (58)52.44 Total impact

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    ABSTRACT: Systems and methods are described for producing liquid crystal devices microwave that use metal alignment layers. The liquid crystal microwave devices include a liquid crystal layer sandwiched between metal layers, which are further sandwiched between substrate layers. At least one of the metal layers is rubbed to form micro-grooves that tend to align the liquid crystal molecules adjacent to those layers without using additional rubbed polymeric layers for the alignment. The thickness of the metal layers can be selected to yield a desired electromagnetic effect, such as constraint of propagation of microwave radiation.
    Ref. No: US8970815 B2, Year: 03/2015
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    Olena Zribi, Yuriy Garbovskiy, Anatoliy Glushchenko
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    ABSTRACT: The biomedical applications of ferroelectric nanoparticles rely on the production of stable aqueous colloids. We report an implementation of the high energy ball milling method to produce and disperse ultrafine BaTiO3 nanoparticles in an aqueous media in a single step. This technique is low-cost, environmentally friendly and has the capability to control nanoparticle size and functionality with milling parameters. As a result, ultrafine nanoparticles with sizes as small as 6 nm can be produced. These nanoparticles maintain ferroelectricity and can be used as second harmonic generating nanoprobes for biomedical imaging. This technique can be generalized to produce aqueous nanoparticle colloids of other imaging materials.
    10/2014; 1(4):045401. DOI:10.1088/2053-1591/1/4/045401
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    ABSTRACT: Fabrication of a thermotropic ferronematic colloid is reported, consisting of a 1% concentration of magnetite nanorods dispersed in a commercially obtained liquid crystal (LC). To produce the nanorods, solvothermal synthesis was utilized by adding Fe(CO)5 to a reaction solution of hexadecylamine and oleic acid in n-octanol. The procedure allows for tailoring of the size and shape of the nanorods. The magnetic nanorods were functionalized with oleic acid. Magneto-optic and electro-optic properties of the colloid were characterized. Specifically, static measurements were performed to determine the birefringence and magnetic and electric Freedericksz thresholds. From the dynamic measurements, the switching time was determined. The nanorods increased the effective magnetic anisotropy of the LC. Depending on nanorod dimensions, the colloid demonstrated faster switching speeds, especially in the presence of crossed electric and magnetic fields.
    IEEE International Magnetics Conference, INTERMAG Europe 2014, Dresden, Germany; 05/2014
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    ABSTRACT: To prepare cholesteric liquid crystalline nonlinear optical materials with ability to be vitrified on cooling and form long time stability cholesteric glasses at room temperature, a series of platinum acetylide complexes modified with cholesterol has been synthesized. The materials synthesized have the formula trans-Pt(PR 3)(cholesterol (3 or 4)-ethynyl benzoate)(1-ethynyl-4-X-benzene), where R = Et, Bu or Oct and X = H, F, OCH 3 and CN. A cholesteric liquid crystal phase was observed in the complexes R = Et, and X = F, OCH 3 and CN but not in any of the other complexes. When X = CN, a cholesteric glass was observed at room temperature which remained stable up to 130 °C, then converted to a mixed crystalline/cholesteric phase and completely melted to an isotropic phase at 230 °C. When X = F or OCH 3 the complexes were crystalline at room temperature with conversion to the cholesteric phase upon heating to 190 and 230 °C, respectively. In the series X = CN, OCH 3 and F, the cholesteric pitch was determined to be 1.7, 3.4 and 9.0 µ, respectively.
    MRS Proceedings, http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9327250&fileId=S1946427414008203; 01/2014
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    Yuriy Garbovskiy, Anatoliy Glushchenko
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    ABSTRACT: In this paper, we will explore how optical and ferroelectric properties of the stressed ferroelectric nanoparticles prepared through ball milling set a limit on the performance of optical and electro-optical devices based on such materials. It was found that suspensions of BaTiO3 nanoparticles exhibit a blue shift in the optical band gap with a decrease in particle size. The optical band gap of PbTiO3 nanoparticles is not affected by the milling time. Polarization switching is composed of slow and fast components. A slow component is threshold-less and is caused by the particle reorientation while a fast component has a threshold, and its rise time is inversely proportional to the electric field. The absorption edge of these suspensions accounts for the applications in the near UV range, while kinetics of the polarization switching governs the speed of electro-optical devices.
    Applied Optics 08/2013; 52(22). DOI:10.1364/AO.52.000E34 · 1.69 Impact Factor
  • Yuriy Garbovskiy, Anatoliy Glushchenko
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    ABSTRACT: In this paper, we will explore how optical and ferroelectric properties of the stressed ferroelectric nanoparticles prepared through ball milling set a limit on the performance of optical and electro-optical devices based on such materials. It was found that suspensions of BaTiO<sub>3</sub> nanoparticles exhibit a blue shift in the optical band gap with a decrease in particle size. The optical band gap of PbTiO<sub>3</sub> nanoparticles is not affected by the milling time. Polarization switching is composed of slow and fast components. A slow component is threshold-less and is caused by the particle reorientation while a fast component has a threshold, and its rise time is inversely proportional to the electric field. The absorption edge of these suspensions accounts for the applications in the near UV range, while kinetics of the polarization switching governs the speed of electro-optical devices.
    Applied Optics 08/2013; 52(22):E34-9. · 1.69 Impact Factor
  • Biophysical Journal 01/2013; 104(2):613-. DOI:10.1016/j.bpj.2012.11.3398 · 3.83 Impact Factor
  • Yuriy Garbovskiy, Olena Zribi, Anatoliy Glushchenko
    Advances in Ferroelectrics, Edited by Dr. Aimé Peláiz-Barranco, 01/2012: chapter Emerging Applications of Ferroelectric Nanoparticles in Materials Technologies, Biology and Medicine; InTec., ISBN: ISBN: 978-953-51-0885-6
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    ABSTRACT: Stressed ferroelectric nanoparticles, less than 10 nm in diameter, are investigated in a nonpolar fluid. Measuring ferroelectric properties of the smallest achieved BaTiO3 ferroelectric nanoparticles allows for the determination of dipole moment and spontaneous polarization as a function of size and concentration; the results are significantly greater than in bulk BaTiO3. This is achieved by using a direct measurement of the displacement current density and either integrating over half a period or fitting the experimental results using the derivative of the Langevin function.
    Physical review. B, Condensed matter 07/2011; 84(2):-. DOI:10.1103/PhysRevB.84.024105 · 3.66 Impact Factor
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    John L West, Ke Zhang, Anatoliy Glushchenko
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    ABSTRACT: In this work we report methods of formation of three-dimensional structures of particles in a liquid crystal host. We found that, under the appropriate conditions, the particles are captured and dragged by the moving isotropic/nematic front during the phase transition process. This movement of the particles can be enhanced significantly or suppressed drastically by application of an electric field and/or by changing the conditions of the phase transition, such as the rate of cooling. As a result, a wide variety of particle structures can be obtained ranging from a fine-grained cellular structure to stripes of varying periods to a course-grained "root" structure. Changing the properties of the materials, such as the size and density of the particles and the surface anchoring of the liquid crystal at the particle surface, can also be used to control the morphology of the three-dimensional particle network and adjust the physical properties of the resulting dispersions. INTRODUCTION Colloidal dispersions of small particles in nematic liquid crystals are a novel, interesting type of soft matter. The difference from ordinary colloids arises from the orientational ordering of the liquid crystal molecules and the resulting structure in the colloid. Topological defects [1, 2] and additional long-range forces between the colloidal particles [3] are immediate consequences of this ordering. The nematic-induced interparticle interaction brings a new range of effects to the system: supermolecular structures [4,6], cellular structures [7,8], and even a soft solid [9] can be observed. Colloidal dispersions in liquid crystals also have a wide variety of potential applications [10]. A range of problems also arises in nematic colloidal dispersions. The nematic ordering makes it difficult to suspend small particles in a liquid crystal host [11]. Particles often segregate into agglomerates distributed non-uniformly in the cell. The resulting spatial distribution of the particles is difficult to control. Our research therefore explores the factors that affect the spatial distribution of these particles and thus control morphology of nanoparticles – liquid crystal colloids. In our previous work, we reported the first demonstration of drag on colloidal particles by a moving nematic-isotropic (NI) interface [12]. We calculated a critical radius above which the particles cannot be captured by the moving interface. We showed that this critical radius is sensitive to the viscous properties of the host liquid crystal, the value of the anchoring coefficient of the liquid crystal on the particle surface, and the velocity of the moving interface. In the experimental work reported here we demonstrate the methods used to control the spatial distribution of particles of different sizes in a liquid crystal cell. We show that a uniform or specially designed non-uniform electric field and/or changing the conditions of the nematic-isotropic phase transition, such as the rate of cooling, can be used to control the morphology of the three-dimensional particle network and adjust the physical properties of the resulting dispersions and displays.
    MRS Online Proceeding Library 01/2011; 776. DOI:10.1557/PROC-776-Q3.8
  • Ke Zhang, Anatoliy Glushchenko, John L. West
    MRS Online Proceeding Library 01/2011; 817. DOI:10.1557/PROC-817-L6.27
  • Yuriy Garbovskiy, Anatoliy Glushchenko
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    ABSTRACT: Nanoparticle/liquid crystal colloidal dispersions are a new, rapidly developing, and exciting frontier of soft matter science and technological progress. This is both because of the dramatic changes in liquid crystal characteristics caused by adding nanoparticles and because of the limited understanding of the structure and interactions of the components of such composite systems. In this review, we summarize the basic science and applications of various nanoparticles, 1–100 nm in diameter, dispersed in liquid crystals. The historical development of this area of science is divided into two main periods. The first period, from the early 1970s until the year 2000, covers the structural organization and the interaction of passive nanoparticles (mostly dielectric) dispersed in liquid crystals. This period initiated the development of novel electro-optic effects and devices based on the properties of such composites. The second period covers progress during the first decade of the millennium. It is a Renaissance era in the development of liquid crystalline nanocolloids when the power of nanoscale was demonstrated to the full extent. Active nanoparticles, mostly ferroelectric, ferromagnetic, and ferroic, added to liquid crystals, shared their intrinsic properties with the liquid crystal host, and allowed for the creation of unprecedented materials with astonishing applications. These active particles generate ultrahigh electric and/or magnetic fields within the liquid crystal host, which, combined with their small size, produces a uniquely exciting and largely unexplored system of composite materials which exhibit novel collective particle–host interactions and which promise a variety of exotic electro-magneto-optic and other applications. These internally generated fields, larger than any macroscopic field that can be applied, serve both to spatially organize the particles and to couple the particle system to the liquid crystal thus enabling the liquid crystal ordering to affect the collective particle order. Although we have made an effort to review liquid crystalline/nanocolloids research as broadly as possible, many great results are omitted from this chapter. We hope this review will be an invitation to further explore this unique and exiting collection of knowledge.
    Solid State Physics 01/2010; 62:1-74. DOI:10.1016/B978-0-12-374293-3.00001-8 · 2.43 Impact Factor
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    ABSTRACT: Liquid crystal alignment is a key process in the production of modern display devices and other liquid crystal based optical elements. The traditional alignment procedures, dealing with treatment of organic films (rubbing, photo-polymerization, ion beam treatment, etc), do not satisfy the increasing demands of modern technology. Because of the presence of a degradable polymer layer, none of these methods provides stability of the liquid crystal orientation for operation in high intensity visible, UV or infrared light. This problem can be solved using anisotropically treated inorganic thin films. The alignment is very sensitive; both polar and azimuthal anchoring energy parameters can be controlled by either conditions of the treatment process or the history of the inorganic film formation. The non-organic nature of the substrates provides non-degrading stability of the liquid crystals alignment while operating in high intensity visible, UV or infrared light. We demonstrate and discuss the use of this technology in many light modulating devices, including high intensity light phase retarders and displays operating at harsh ambient conditions.
    Proceedings of SPIE - The International Society for Optical Engineering 05/2009; DOI:10.1117/12.821413 · 0.20 Impact Factor
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    ABSTRACT: A review of the theoretical and experimental results for tunable microwave band-stop filters, band-pass filters, phase shifters, and a signal-to-noise enhancer, all based on a microstrip geometry and using a variety of magnetic thin films and layered structures, is presented. These devices are compatible in size and growth process with on-chip high-frequency electronics. For devices based on metallic ferromagnetic films of Fe and Permalloy, the operational frequency ranges from 5 to 35 GHz for external fields below 5 kOe.
    43th Annual GOMACTech Conference; 03/2009
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    ABSTRACT: The gain characteristics of liquid crystal photorefractive cells doped with ferroelectric nanoparticles has been measured. The liquid crystal two beam coupling gain is found to reverse in sign and increase in magnitude through the addition of ferroelectric BaTiO(3) nanoparticles, yielding gain coefficients up to 1100 cm(-3) in the Bragg regime. We attribute the novel effects of gain reversal and magnitude increase to interactions between the ferroelectric particles' spontaneous polarization and the local liquid crystal flexopolarization.
    Optics Express 04/2008; 16(6):4015-22. DOI:10.1364/OE.16.004015 · 3.53 Impact Factor
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    ABSTRACT: We report on the photorefractive properties of liquid crystals sandwiched between windows of cerium doped strontium barium niobate (Ce:SBN). This adaptable design has been used to create devices using pure nematic liquid crystals, ferroelectric nanoparticle doped liquid crystals, and cholesteric liquid crystals. In all these systems, modulation of the liquid crystal molecules is driven by the surface space-charge field from the inorganic windows. Owing to the large effective trap density in the Ce:SBN, high resolution gratings with two-beam coupling gain coefficients of up to 1400 cm<sup>-1</sup> have been achieved in the Bragg regime.
    IEEE/LEOS Winter Topical Meeting Series, 2008; 02/2008
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    ABSTRACT: a b s t r a c t We present a review of theoretical and experimental results for tunable microwave band-stop filters, band-pass filters, phase shifters, and a signal to noise enhancer, all based on a microstrip geometry and using a variety of magnetic thin films and layered structures. These devices are compatible in size and growth process with on-chip high-frequency electronics. For devices based on metallic ferromagnetic films of Fe and Permalloy, the operational frequency ranges from 5 to 35 GHz for external fields below 5 kOe. For the band-stop filters, we observed power attenuation up to $100 dB/cm, and an insertion loss on the order of $2–3 dB, for both Permalloy and Fe-based structures. We also explore the use of thin films of hexagonal ferrites, antiferromagnets, and liquid crystals, and show that useful devices can be constructed with films less than one 1 mm in thickness. & 2008 Elsevier B.V. All rights reserved.
    Journal of Magnetism and Magnetic Materials 01/2008; 321(14). DOI:10.1016/j.jmmm.2008.04.125 · 2.00 Impact Factor
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    ABSTRACT: In this paper, we report on the influence of sub-micron ferroelectric particles on optical, dielectric and electro-optical properties of cholesteric host. An ultra-small fraction of ferroelectric nanoparticles in a cholesteric liquid crystal greatly increases the birefringence of the latter and its dielectric anisotropy that results in a broadening of the reflection band, decreasing of the driving voltage of the switching between bistable textures and in an increasing of its steepness. 1. Introduction A supramolecular helical structure of chiral nematic liquid crystals (cholesterics) brings a lot of fascinating properties. If the helical pitch is comparable to the wavelength of light a distributed optical feedback results in selective light reflection and giant optical activity. Effective control of helical pitch value and chiral structures of cholesterics by external field and temperature makes cholesterics extremely promising for uses in photonic and electro- optic devices, such as photonic crystals, light shutters and switches, adaptive laser-optics and lasing. Effect of electric-field-driven texture transition between planar and focal conic textures makes a base of operation of bistable cholesteric displays (1), future of which looks incredible due to fascinating possibility to make flexible polymer bistable LCD's by roll-to-roll technology (2). Despite substantial advantages, a wide use of cholesteric LCD's is still restrained by high driving voltages and rather low contrast of the devices. Therefore, development of new cholesteric materials is a crucial task for a widespread application of cholesteric LCD's. Recently a new class of LC systems has been proposed - diluted colloids of ferroelectric nanoparticles in nematic matrixes (3-4). These systems macroscopically appear identical to a pure nematics providing, however, strongly enhanced optical and electro-optical properties. In particular, ferroelectric nanoparticles strongly increase dielectric anisotropy and birefringence of the nematic host. Our preliminary studies also showed advanced characteristics of cholesterics doped with ferroelectric nanoparticles. Introducing the particles leads to the decrease of driving voltages, increase of the both reflection contrast and the steepness of the transition (5).
    SID Symposium Digest of Technical Papers 05/2007; 38(1). DOI:10.1889/1.2785495
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    John L. West, Fenghua Li, Ke Zhang, Hari M. Atkuri, Anatoliy V. Glushchenko
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    ABSTRACT: We enhance the electro-optic performance of liquid crystals by dispersing ferroelectric nanoparticles. Devices using these dispersions have lower driving voltages, faster switching speeds and higher contrast ratios. These changes are caused by increases in the dielectric anisotropy, birefringence and elastic constants and can be used to produce improved displays.
    SID Symposium Digest of Technical Papers 05/2007; 38(1). DOI:10.1889/1.2785496
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    ABSTRACT: We present results of beam coupling from hybrid photorefractive cells comprising a liquid crystal layer doped with nano-particles of ferroelectric materials adjacent to doped inorganic photorefractive windows. The presence of the nano-particles significantly enhances the optical coupling between the signal beam and pump beam. Full Bragg matched amplification of a signal beam is demonstrated for grating spacings from 5μm to less than 800nm.

Publication Stats

559 Citations
52.44 Total Impact Points

Institutions

  • 2006–2014
    • University of Colorado Colorado Springs
      • Department of Physics
      Colorado Springs, Colorado, United States
    • Ukrainian Academy of Agrarian Sciences
      Kievo, Kyiv City, Ukraine
  • 1709–2011
    • Kent State University
      • Liquid Crystal Institute
      Kent, Ohio, United States
  • 2007
    • University of Colorado
      • Department of Physics
      Denver, Colorado, United States