Water-Templated Growth of Interfacial Superglue Polymers for Tunable Thin Films and In Situ Fluid Encapsulation.

Thin polymer films (TPFs) are indispensable elements in numerous technologies ranging from liquid encapsulation to biotechnology to electronics. However, their production typically relies on wet chemistry involving organic solvents or chemical vapor deposition, necessitating elaborate equipment and often harsh conditions. Here, an eco-friendly, fast, and facile synthesis of water-templated interfacial polymers based on cyanoacrylates (superglues, CAs) that yield thin films with tailored properties is demonstrated.

Surface alignment of nematic liquid crystals by direct laser writing of photopolymer alignment layers.

We demonstrate the fabrication of good quality surface alignment layers on glass by Direct Laser Writing method using a 2-photon polymerisation technique. We use commercially available photosensitive resins to print alignment layers by scanning the focal point of a femtosecond laser near the resin-glass interface. This results in down to ~ 100 nm thin alignment layers that provide good planar anchoring of 5CB and MLC13300, with the easy axis of alignment along the scanning direction.

Neural networks determination of material elastic constants and structures in nematic complex fluids.

Supervised machine learning and artificial neural network approaches can allow for the determination of selected material parameters or structures from a measurable signal without knowing the exact mathematical relationship between them. Here, we demonstrate that material nematic elastic constants and the initial structural material configuration can be found using sequential neural networks applied to the transmmited time-dependent light intensity through the nematic liquid crystal (NLC) sample under crossed polarizers. Specifically, we simulate multiple times the relaxation of the NLC from a random (qeunched) initial state to the equilibirum for random values of elastic constants and, simultaneously, the transmittance of the sample for monochromatic polarized light.

Amyloid Fibrils of Stefin B Show Anisotropic Properties.

Human stefin B, a member of the cystatin family of cysteine protease inhibitors, tends to form amyloid fibrils under relatively mild conditions, which is why it is used as a model protein to study amyloid fibrillation. Here, we show for the first time that bundles of amyloid fibrils, i.e.

Flexoelectric Polarization in a Nematic Liquid Crystal Enhanced by Dopants with Different Molecular Shape Polarities.

Flexoelectricity may have an important impact on the switching properties of nematic and cholesteric liquid crystals due to the linear coupling between the flexoelectric polarization of the liquid crystal and the applied electric field. This coupling is the origin of the extraordinary electro-optic effect in cholesterics aligned in the uniform lying helix texture, resulting in fast switching and field control of both rise and fall times. Therefore, the flexoelectric properties of the liquid crystals have become an important issue when designing and synthesizing liquid crystal materials and/or preparing their mixtures with appropriate flexoelectric compounds (dopants).

Supramolecular Polymorphism of (GC) Repeats Associated with ALS and FTD.

Guanine-rich DNA sequences self-assemble into highly stable fourfold structures known as DNA-quadruplexes (or G-quadruplexes). G-quadruplexes have furthermore the tendency to associate into one-dimensional supramolecular aggregates termed G-wires. We studied the formation of G-wires in solutions of the sequences d(GC) with = 1, 2, and 4.

Nematic Liquid-Crystal Necklace Structure Made by Microfluidics System.

We report a necklace structure made of liquid crystal dispersed in poly(vinyl alcohol) (PVA) aqueous solution, which is fabricated by a microfluidic device. In the necklace structure, liquid crystal droplets that are tens of micrometers in diameter are connected by microtethers, which are birefringent, are not penetrating the droplets, and can be elastically stretched by applying external force. The necklace structure was analyzed by fluorescent confocal microscopy, and the tethers were made of liquid crystal and PVA composite.

Lamellar liquid crystals maintain keratinocytes' membrane fluidity: An AFM qualitative and quantitative study.

Despite extensive investigations of lamellar liquid crystals for dermal application, the effects of these systems at the cellular level are still not well elucidated. The key aim of this study was to determine the elasticity and morphological features of keratinocytes after exposure to a lamellar liquid crystal system (LLCS) using atomic force microscopy (AFM) as the method of choice. Prior to AFM assessment, a cell proliferation test and light plus fluorescence imaging were applied to determine the sub-toxic concentration of LLCS.

Nanoparticles Can Wrap Epithelial Cell Membranes and Relocate Them Across the Epithelial Cell Layer.

Although the link between the inhalation of nanoparticles and cardiovascular disease is well established, the causal pathway between nanoparticle exposure and increased activity of blood coagulation factors remains unexplained. To initiate coagulation tissue factor bearing epithelial cell membranes should be exposed to blood, on the other side of the less than a micrometre thin air-blood barrier. For the inhaled nanoparticles to promote coagulation, they need to bind lung epithelial-cell membrane parts and relocate them into the blood.

Optothermally driven colloidal transport in a confined nematic liquid crystal.

We demonstrate transport of microparticles by rapid movement of a laser spot in a thin layer of a nematic liquid crystal. The transport is achieved by fluid flow, caused by two different mechanisms. The thermoviscous expansion effect induces colloidal transport in the direction opposite to the laser movement, whereas thermally induced local melting of the liquid crystal pulls the particles in the direction of the laser movement.

Dynamics of topological monopoles annihilation on a fibre in a thick and thin nematic layer.

We study topological defect annihilation on a glass fibre with homeotropic surface anchoring of nematic liquid crystal molecules. The fibre is set parallel to the nematic director of a planar cell with variable thickness and we create pairs of Saturn ring and Saturn anti-ring using the laser tweezers. In thick cells we observe in the whole region of defect separation a Coulomb-like pair attraction with no background force, [Formula: see text] with [Formula: see text].

Annihilation dynamics of topological monopoles on a fiber in nematic liquid crystals.

We use the laser tweezers to create isolated pairs of topological point defects in a form of radial and hyperbolic hedgehogs, located close and attracted to a thin fiber with perpendicular surface orientation of nematic liquid crystal molecules in a thin planar nematic cell. We study the time evolution of the interaction between the two monopoles by monitoring their movement and reconstructing their trajectories and velocities. We find that there is a crossover in the pair interaction force between the radial and hyperbolic hedgehog.

Surface charge and interactions of 20-nm nanocolloids in a nematic liquid crystal.

We studied real-time motion of individual 20-nm silica nanoparticles in a thin layer of a nematic liquid crystal using a dark-field optical videomicroscopy. By tracking the positions of individual nanoparticles we observed that particle pair interactions are not only mediated by strong thermal fluctuations of the nematic liquid crystal, but also with a repulsive force of electric origin. We determined the total electric charge of silanated silica particles in the nematic liquid crystal 5CB by observing the electric-force-driven drift.

Topological defect transformation and structural transition of two-dimensional colloidal crystals across the nematic to smectic-A phase transition.

We observe that topological defects in nematic colloids are strongly influenced by the elasticity and onset of smectic layering across the nematic (N) to smectic-A (SmA) phase transition. When approaching the SmA phase from above, the nematic hyperbolic hedgehog defect that accompanies a spherical colloidal inclusion is transformed into a focal conic line in the SmA phase. This phase transformation has a strong influence on the pairwise colloidal interaction and is responsible for a structural transition of two-dimensional colloidal crystals.

The effect of tyrosine residues on α-synuclein fibrillation.

Aggregation of the intrinsically disordered protein α-synuclein into ordered amyloid fibrils is implicated in the pathogenesis of Parkinson's disease. To unravel the role of Tyr residues in α-synuclein fibrillation, we prepared recombinant N-terminal (Y39A) and C-terminal (Y(125,133,136)A) mutants of α-synuclein and examined their fibrillation propensities by thioflavin T and 1-anilinonaphthalene-8-sulfonate (ANS) fluorescent probes, SDS-PAGE and atomic force microscopy. We demonstrate that in contrast to wild-type α-synuclein, both mutants show large, but comparable delays in the fibrillation process and exhibit enhanced hydrophobicity during fibril-like assembly.

Topological binding and elastic interactions of microspheres and fibres in a nematic liquid crystal.

We present a detailed analysis of topological binding and elastic interactions between a long, and micrometer-diameter fiber, and a microsphere in a homogeneously aligned nematic liquid crystal. Both objects are surface treated to produce strong perpendicular anchoring of the nematic liquid crystal. We use the opto-thermal micro-quench of the laser tweezers to produce topological defects with prescribed topological charge, such as pairs of a Saturn ring and an anti-ring, hyperbolic and radial hedgehogs on a fiber, as well as zero-charge loops.

In situ laser-imprinted surface realignment of a nematic liquid crystal.

We present a new method for the in-plane realignment of nematic liquid crystals in already fully assembled cells with uni-directionally rubbed polyimide as an aligning layer. We use nematic liquid crystals (NLCs) with a relatively high nematic-isotropic transition temperature and we focus the IR laser beam of the laser tweezers selectively onto one or the other of the inner interfaces. The heat generated by the IR absorption locally melts the liquid crystal and creates an isotropic island with well-defined molecular anchoring at the nematic-isotropic interface.

Synthesis of bioactive β-TCP coatings with tailored physico-chemical properties on zirconia bioceramics.

The objective of this work was to develop a synthesis procedure for the deposition of β-TCP coatings with tailored physico-chemical properties on zirconia bioceramics. The synthesis procedure involved two steps: (i) a rapid wet-chemical deposition of a biomimetic CaP coating and (ii) a subsequent post-deposition processing of the biomimetic CaP coating, which included a heat treatment between 800 and 1200 °C, followed by a short sonication in a water bath. By regulating the heating temperature the topography of the β-TCP coatings could be controlled.

The role of initial oligomers in amyloid fibril formation by human stefin B.

Oligomers are commonly observed intermediates at the initial stages of amyloid fibril formation. They are toxic to neurons and cause decrease in neural transmission and long-term potentiation. We describe an in vitro study of the initial steps in amyloid fibril formation by human stefin B, which proved to be a good model system.

Light-induced rewiring and winding of Saturn ring defects in photosensitive chiral nematic colloids.

We study the winding and unwinding of Saturn ring defects around silica microspheres with homeotropic surface anchoring in a cholesteric liquid crystal with a variable pitch. We use mixtures of a nematic liquid crystal 5CB and various photoresponsive chiral dopants to vary the helical pitch and sense of the helical winding by illuminating the mixtures with UV or visible light. Upon illumination, we observe motion of the Grandjean-Cano disclination lines in wedge-like cells.

The design trend in tissue-engineering scaffolds based on nanomechanical properties of individual electrospun nanofibers.

This paper especially highlights the finding that the mechanical properties of polymeric nanofibers can be tuned by changing the fiber size as well as the composition. For this purpose, the bending Young's modulus was determined using atomic force microscope by involving single-material (polyvinyl alcohol (PVA), polyethylene oxide (PEO 400K)) and composite nanofibers (polyvinyl alcohol/hyaluronic acid (PVA/HA), polyethylene oxide/chitosan (PEO 400K/CS)). The mechanical property, namely the bending Young's modulus, increases as the diameter of the fibers decreases from the bulk down to the nanometer regime (less than 200 nm).

Consolidation trend design based on Young's modulus of clarithromycin single crystals.

The key aim of this study was to determine single mechanical properties of clarithromycin polymorphic forms in order to select some of them as more suitable for the tableting process. For this purpose, AFM single-point nanoindentation was used. The Young's moduli of clarithromycin polymorphs were substantially different, which was consistent with the structural variations in their packing motifs.

Transport of particles by a thermally induced gradient of the order parameter in nematic liquid crystals.

We demonstrate manipulation and transport of microparticles and even fluorescent molecules by the thermally induced gradient of the order parameter in the nematic liquid crystal. We use IR light absorption of the tightly focused beam of laser tweezers to heat locally a thin layer of the nematic liquid crystal by several degrees. This creates a spatial gradient of temperature of the nematic liquid crystal over separations of several tens of micrometers.

Chirality screening and metastable states in chiral nematic colloids.

We show that forces between two colloidal particles in a thin layer of a chiral nematic liquid crystal strongly depend on the chirality of the liquid crystal. The observed pair potentials are attractive, but are oscillatory functions of colloidal separation. The number and the position of local energy minima increase with increasing chirality.