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ABSTRACT: Self-assembled cylindrical lipid tubules have attracted attention as templates for synthesizing hybrid organic-inorganic materials. Here we report the synthesis of hybrid silica-lipid cylinders by sol-gel condensation of tetraethoxysilane (TEOS) on helical rippled tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phospho-choline (DC 8,9 PC). Transmission electron microscopy reveals that the nanoscale helical ripples of the lipid tubules are transcripted to the templated silica films. On the other hand, the deposition of the silica films substantially improves the thermal stability of lipid tubules. We find that the crystalline ordering of lipid bilayer walls confined in the hybrid silica-lipid cylinders is stable up to 110 °C.
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ABSTRACT: The mechanical behavior of self-assembled lipid tubules is an important property which determines their suitability for technological applications. We study the instability of multibilayer lipid tubules (with wall thickness t and external radius R(ext)) beyond elastic response under local radial atomic force microscopy indentations. A discontinuity in force-distance curves associated with the buckling instability of lipid tubules is observed. The critical force at which lipid tubules undergo a buckling transition linearly scales as t/R(ext). In addition, a reduced critical buckling force is found to extend a distance of approximately 1 microm from the end of lipid tubules.
Physical Review E 08/2009; 80(2 Pt 1):021911. · 2.26 Impact Factor
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ABSTRACT: An electrically tunable wettability in a liquid crystal/ polymer composite film is demonstrated, in which liquid crystal molecules are anchored among polymer grains. The tunable wettability of the composite films originates from the reorientation of the anchored liquid-crystal molecules, which is switched by an in-plane electric field with squared pulses of voltages. These liquid crystal/polymer composite films with electrically tunable wettability have potential applications in polarizer-free displays, ink-jet printing, microfluidic devices, and lab-on-a-chip.
Optics Express 11/2008; 16(22):17591-8. · 3.59 Impact Factor
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ABSTRACT: We report a method based on poly(dimethylsiloxane) (PDMS) stamp-assisted moving contact line to bend lipid tubules into zigzags on glass substrates. Atomic force microscopy (AFM) reveals that the zigzag lipid tubules buckle at the bent sites. The measurements of buckling heights as a function of bending angles suggest a gradual buckling mode. By imaging the zigzag tubules with AFM under different loading forces, we study the correlation between the loading force and the tubule compression. The reduced stiffness at the buckling sites of zigzag tubules suggests that lipid molecules are reorganized during the gradual buckling.
The Journal of Physical Chemistry B 10/2008; 112(35):10964-8. · 3.70 Impact Factor
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ABSTRACT: We report an experimental and theoretical study of the radial elasticity of tobacco mosaic virus (TMV) nanotubes. An atomic force microscope tip is used to apply small radial indentations to deform TMV nanotubes. The initial elastic response of TMV nanotubes can be described by finite-element analysis in 5nm indentation depths and Hertz theory in 1.5nm indentation depths. The derived radial Young's modulus of TMV nanotubes is 0.92+/-0.15GPa from finite-element analysis and 1.0+/-0.2GPa from the Hertz model, which are comparable with the reported axial Young's modulus of 1.1GPa [Falvo, Biophys. J. 72, 1396 (1997)].
Physical Review E 10/2008; 78(3 Pt 1):031914. · 2.26 Impact Factor
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ABSTRACT: Some high birefringence ester liquid crystal compounds with cyanate or isothiocyanate polar groups were investigated, the relaxation frequency of which is in the kilo‐Hertz region. These compounds are useful for formulating dual‐frequency liquid crystal (DFLC) mixtures. The dielectric relaxation and electro‐optical properties of these compounds were characterised. Potential applications of these compounds for DFLC mixtures to meet different requirements are discussed.
Liquid Crystals. 09/2008; 35(9):1129-1135.
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ABSTRACT: Self-assembled lipid tubules with crystalline bilayer walls represent useful supramolecular architectures which hold promise as vehicles for the controlled release of preloaded drugs and templates for the synthesis of one-dimensional inorganic materials. We study the local elasticity of lipid tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine by radial atomic force microscope indentation, coupled with finite element analysis. A reduced stiffness is found to extend a distance of approximately 600 nm from the ends of lipid tubules. The middle section of lipid tubules is homogeneous in terms of their radial elasticity with a Young's modulus of approximately 703 MPa. The inhomogeneous radial elasticity likely arises from the variation of lipid packing density near the tubule ends.
ACS Nano 08/2008; 2(7):1466-72. · 10.77 Impact Factor
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ABSTRACT: Lipid tubules formed by rolled-up bilayer sheets have shown promise in drug delivery systems, nanofluidics, and microelectronics. Here we report a method for directly printing lipid tubules on substrates. Preformed lipid tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine are aligned in the recessed channels of a thin poly(dimethylsiloxane) (PDMS) stamp. The aligned lipid tubules then serve as an "ink" for microcontact printing. We demonstrate that two-dimensional (2-D) arrays of aligned lipid tubules can be transferred onto planar, patterned, and curved substrates from the recessed channels of the PDMS stamp by bringing the tubule-inked PDMS stamp into contact with these substrates. We show that the 2-D array of aligned lipid tubules can be transcribed into a 2-D array of aligned silica cylinders through templated sol-gel condensation of tetraethoxysilane.
Langmuir 06/2008; 24(9):5113-7. · 4.19 Impact Factor
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ABSTRACT: Self-assembled hollow lipid tubules are interesting and potentially useful supramolecular structures. Here, we study the deformation of lipid tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) trapped inside liquid droplets on glass substrates. The interface tension of the shrinking liquid droplets exerts a compression force on the ends of the trapped lipid tubules, and causes them to buckle. This provides a method to measure their mechanical properties. The Young's modulus of the DC8,9PC lipid tubules is estimated to approximately 1.07 GPa. As the strain energy of the buckled tubules builds up, they poke through the interface of shrinking liquid droplets and then adhere onto glass substrates to form looplike shapes.
Nano Letters 06/2007; 7(5):1360-3. · 13.20 Impact Factor
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ABSTRACT: Self-assembled cylindrical lipid tubules have attracted attention as templates for synthesizing hybrid organic−inorganic materials. Here we report the synthesis of hybrid silica−lipid cylinders by sol−gel condensation of tetraethoxysilane (TEOS) on helical rippled tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC8,9PC). Transmission electron microscopy reveals that the nanoscale helical ripples of the lipid tubules are transcripted to the templated silica films. On the other hand, the deposition of the silica films substantially improves the thermal stability of lipid tubules. We find that the crystalline ordering of lipid bilayer walls confined in the hybrid silica−lipid cylinders is stable up to 110 °C.
04/2007;
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ABSTRACT: Lipid tubules represent a hollow, cylindrical supramolecular structure formed by rolled-up lipid bilayers. We find that the lipid tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine can be bent into a loopike shape by the shrinking contact line of droplets on self-assembled monolayers (SAMs) of 1-dodecanethiol. The persistence length of individual lipid tubules is estimated to be approximately 41 microm. The radial deformation of the lipid tubules on SAMs is studied under applied load using atomic force microscope. The stiffness of the tubules in the radial direction is found to increase when the number of the lipid bilayers in the tubule wall increases.
The Journal of Physical Chemistry B 12/2006; 110(44):22060-3. · 3.70 Impact Factor
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Small 04/2006; 2(3):364-7. · 8.35 Impact Factor
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ABSTRACT: A lightweight in-plane-switching liquid crystal display (IPS-LCD) using a single glass substrate and an anisotropic polymeric film is demonstrated. The liquid crystal molecules are aligned by the elongated polymer grain of the film. The alignment capability of the anisotropic film is comparable to a buffed polyimide layer. Compared to the LCD using two glass substrates, our new device exhibits a comparable contrast ratio (∼514:1), driving voltage, and response time because of good LC alignment. Such an anisotropic film can also function as a phase compensation film for widening the viewing angle. This technology is particularly attractive for making single-substrate displays and also has potential for a double-layered guest-host display and a flexible display using IPS LCDs.
Journal of Display Technology 04/2006; · 2.28 Impact Factor
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ABSTRACT: Self-assembled cylindrical tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC(8,9)PC) have been studied by atomic force microscopy in both the height and amplitude modes. Nanoscale ripple structures in the cylindrical lipid tubules are clearly resolved in amplitude mode images. The periodicity of the ripples is found to be 200 +/- 30 nm for tubules with diameters in the range from 200 to 650 nm. The angle of the ripples with respect to the equator of the tubules shows a bimodal distribution with centers at approximately 28 degrees and approximately 5 degrees.
Langmuir 03/2006; 22(5):1973-5. · 4.19 Impact Factor
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ABSTRACT: This paper presents a method for positioning and aligning self-assembled tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphochloline (DC(8,9)PC) by withdrawing a patterned Au substrate from tubule solution. The patterned Au substrates with alternating bare Au stripes and thiol monolayer stripes are formed by microcontact printing. We find that the lipid tubules selectively adsorb on the bare Au stripes but show no orientation order. By withdrawing the patterned Au substrates at the direction along the stripes from tubule solution, the lipid tubules are found to be aligned along the direction of the Au stripes. The angular distribution and the density of the aligned lipid tubules depend on the withdrawal rates and the adsorption time, respectively. We conclude that forces causing tubule alignment that originate in the surface tension associated with the moving meniscus dominate alignment forces exerted by the patterned Au substrates.
Langmuir 03/2006; 22(4):1891-5. · 4.19 Impact Factor
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ABSTRACT: A polarization-independent phase-only liquid crystal (LC) phase modulator using a double-layered structure is demonstrated. Two orthogonal LC layers are separated by two ultra-thin anisotropic polymer films. The anisotropic polymeric films not only separate the LC layers but also provide good molecular alignment. As a result, a polarization-independent phase modulator with 2pi phase shift is achieved at 9Vrms and 8.1pi at 40Vrms using a 12-microm-thick E7 LC layers. This operating voltage is ~10X lower than that using a conventional 0.3-mm-thick glass separator.
Optics Express 11/2005; 13(22):8746-52. · 3.59 Impact Factor
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ABSTRACT: Self-assembled cylindrical tubules of chiral phospholipids are interesting supramolecular structures. Understanding the molecular-tilt order is a key step in controlling the size and shape of the tubules and designing new functional materials. The current theories based on the chiral interactions, coupled with molecular tilt, have predicted that the tubules could have both uniform and modulated tilt states. Here, we image the molecular-tilt order in the self-assembled tubules of a chiral phospholipid by using liquid crystals as an optical amplification probe. We demonstrate that the organization of the molecular-tilt azimuth in the lipid tubules can induce an azimuthal orientation in the liquid crystals. Both uniform and modulated tilt states of the lipid tubules are observed after liquid-crystal optical amplification.
Proceedings of the National Academy of Sciences 06/2005; 102(21):7438-42. · 9.68 Impact Factor
