Fingerprint Texture Research Articles

Branched-arm macromolecule liquid crystals-containing fluorine and isosorbide-structure and properties

A new series of cholesteric fluorated branched-arm liquid crystals (CHFBALCs) compound (MFA1–MFA4), with isosorbide as chiral core, was synthesized. Four precursors of branched-arm FA1–FA4 were obtained firstly and then were esterized separately with isosorbide to get four chiral branched-arm liquid crystalline (MFA1–MFA4). The structures and properties were characterized by conventional spectrum methods, thermal analysis and texture analysis. The results showed that FA1–FA4 all were nematic phase with schlieren, threaded-like or droplet texture. When the isosorbide was successfully inducted, the phase of FA1–FA4 turned into cholesteric phase with oily streak texture, finger print texture or cholesteric droplets. The values of melting point and clearing point for FA1–FA4 and MFA1–MFA4 all changed irregularly, which may be due to the effect of different branched arm, warping of chiral agent and fluorine atom. MFA1–MFA4 had the same handedness as isosorbide core and did not show selective reflection. MFA3 and MFA4 were hopeful to realize the combination of the processability of polymers and the mobility of small molecules.

Flexibility and color monitoring of cellulose nanocrystal iridescent solid films using anionic or neutral polymers.

One property of sulfated cellulose nanocrystals (CNCs) is their ability to self-assemble from a concentrated suspension under specific drying conditions into an iridescent film. Such colored films are very brittle, which makes them difficult to handle or integrate within an industrial process. The goal of this study is (i) to produce flexible films using neutral poly(ethylene glycol) (PEG) and (ii) to modulate their coloration using an anionic polyacrylate (PAAS). The first part is dedicated to studying the physicochemical interactions of the two polymers with CNCs using techniques such as zeta potential measurements, dynamic light scattering (DLS), quartz crystal microbalance (QCM), and atomic force microscopy (AFM). Iridescent solid films were then produced and characterized using scanning electron microscopy (SEM) and UV-visible spectroscopy. The mechanical and thermal properties of films incorporating CNC were measured to evaluate improvements in flexibility. The addition of 10 wt % of PEG makes these films much more flexible (with a doubling of the elongation), with the coloration being preserved and the temperature of degradation increasing by almost 35 °C. Up to 160 μmol/gCNC PAAS can be added to tune the coloration of the CNC films by producing a more narrow, stronger coloration in the visible spectrum (higher absorption) with a well-pronounced fingerprint texture.

Pyrene-Naphthalene Diimide-Pyrene Triad의 합성 및 물성에 대한 연구

In this study, we presented a newly synthesized pyrene-naphthalene diimide(NDI)-pyrene triad. The optical and structural properties were examined using various characterization techniques. A donor-acceptor-donor triad molecule exhibited a strong charge transfer, though there existed neither intramolecular nor intermolecular hydrogen bonding sites, due to the formation of preferential complementary complex between pyrene and NDI. Powder XRD measurement revealed a sharp and distinctive X-ray patterns, indicating the presence of microcrystalline-like structure. POM images showed anisotropic fingerprint texture similar to that of cholesteric phase, and SEM images showed numerous columnar structures with length of 1 to 10μm. Above observation clearly demonstrated that π-complementary NDI-pyrene interactions in the traid was strong enough to form columnar aggregates in the long range.

Electrically switchable multi-stable cholesteric liquid crystal based on chiral ionic liquid.

A multi-stable and electrically switchable cholesteric liquid crystal based on chiral ionic liquid is demonstrated. The cholesteric liquid crystal can be switched among the planar texture, focal conic texture, wide-band reflected state, and fingerprint texture by applying specific electric fields. Each of these four states exists stably for several hours without any obvious change observed at room temperature. The electro-optical properties and driving scheme of the cholesteric liquid crystal are also reported.

Influence of spacer moiety and length of end chain for the phase stability in complementary, double hydrogen bonded liquid crystals, MA:nOBAs

Supra molecular liquid crystals formed by the Hydrogen Bonding interaction between a non-mesogenic aliphatic dicarboxylic acid viz., COOHCH2COOH (Malonic Acid, MA); and mesogenic aromatic, N-(p-n-alkoxy benzoic)Acids, (i.e., nOBAs) for n=3, 4, 5, 7, 8, 9, 10, 11 and 12, labeled as nOBA:COOH[CH2]mCOOH:nOBAs, abbreviated as MA:nOBAs are reported. 1H NMR and 13C NMR studies confirm the formation of HBLC complexes. Infrared (IR) studies confirm the complementary, double, alternative type of HB. Polarized Optical Microscopy (POM) and Differential Scanning Calorimetry (DSC) studies infer N, SmC, SmX, SmCRE, SmF, SmG LC phase variance. SmX phase exhibiting finger print texture grows in MA:nOBAs for n=10, 11 and 12 by the interruption of SmC phase with decreasing temperature. Re-Entrant SmC (SmCRE) grows by the cooling of SmX. I–N, N–C, X–CRE, C–G, CRE–F, F–G and G–Solid transitions exhibit first order nature. C–X is found to be second order nature in n=10 and 11. C–X in n=12 and X–CRE and CRE–F transitions are found to be weak first order nature. Influence of lengths of end chain (n) and spacer (m) for the overall LC phase [ΔT]LC; tilted phase [ΔT]Tilt; SmC phase [ΔT]C and SmX phase [ΔT]X stabilities is discussed in the wake of data on other HBLCs with similar molecular structure. Prevalence of SmX phase in MA:nOBAs with m=1 infers repulsive interaction between the π-electronic cloud of aromatic boards of nOBAs. Model molecule predicts a twisted configuration of π-cloud around the molecular long axis. Finger print texture of SmX validates the model.

Morphology and optical properties of chiral polymer films containing hetero-atoms prepared by electrochemical polymerisation in a cholesteric liquid crystal

Synthesis of chiral films in chiral liquid crystal is reported. The monomers (3, 3′-hexylsilane-2, 2′-bithiophene and 3,6-bis(3, 4-ethylenedioxythienyl)pyridazine) in cholesteric liquid crystal (CLC) electrolyte solution were elecropolymerised by the application of voltage to yield a thin film. Circular dichroism measurements display the Cotton effect for the films. The polymers show a fingerprint texture very similar to that of the CLC. The structure developed during polymerisation was preserved even after washing. Note that no chiral molecule reacted chemically with the monomer during polymerisation. The electrolyte functioned as a chiral matrix. This simple method can be defined as asymmetric polymerisation in chiral environment.

カ イ ラ ルネマチッ ク 液晶の指紋状組織パタ ーンの縞方向情報による類似度評価

カ イ ラ ルネマチッ ク 液晶の指紋状組織パタ ーンの縞方向情報による類似度評価

Syntheses and Characterization of Chiral Branched-Arm Liquid Crystals-Basing on Isosorbide as Chiral Core

A new series of two-arm (MB1, MB2), four-arm (MB3), six-arm (MB4) chiral liquid crystalline compound containing isosorbide as chiral core were first synthesized. Four precursors of branched-arm B1~B4 were obtained at first and then were esterized separately with isosorbide and got four chiral branched-arm liquid crystals (MB1~MB4). The chemical structures and LC properties of the liquid crystalline molecule were measured by spectrum and thermal analysis techniques. XRD curves of MB1~MB4 samples only showed broad peaks at wide-angle, but no sharp peak was seen for all the samples. The results showed that MB1~MB4 appeared cholesteric phase with oily streak texture or lined texture and finger print texture. Isosorbide successfully induced cholesteric phase. The values of melting point and clearing point for MB1~MB4 decreased. The quantity of branched-arm and chiral core had effects on their liquid crystalline properties.

Influence of degree of sulfation on the rheology of cellulose nanocrystal suspensions

The rheology and microstructure of two different cellulose nanocrystals (CNC) samples possessing different degrees of sulfation are studied over a broad concentration range of 1 to 15 wt%. CNC suspensions are isotropic at low concentration and experience two different transitions as concentration increases. First, they form chiral nematic liquid crystals above a first critical concentration where the samples exhibit a fingerprint texture and the viscosity profile shows a three-region behavior, typical of liquid crystals. By further increasing the concentration, CNC suspensions form gels above a second critical concentration, where the viscosity profile shows a single shear-thinning behavior over the whole range of shear rates investigated. It has been found that the degree of sulfation of CNC particles has a significant effect on the critical concentrations at which transitions from isotropic to liquid crystal and liquid crystal to gel occur. Rheological properties and microstructure of these suspensions have been studied using polarized optical microscopy combined with rheometry.

Cholesteric liquid crystal–carbon nanotube composites with photo-settable reversible and memory electro-optic modes

The photoresponsive electro-optical composites based on cholesteric liquid crystal (CLC) with optically controlled chirality and a minute amount of carbon nanotubes (CNTs) are studied. In cells with homeotropic anchoring, these composites exhibit a transition from fingerprint texture to homeotropic nematic texture in the course of photoinduced unwinding of the cholesteric helix. Compared with the CLC counterpart, this transition is much delayed, because of the stabilization of cholesteric filamentary domains by CNTs. The CLC-CNT composites demonstrate dual-mode operation with optical switching between reversible and memory mode. It is found that the memory response is associated with the elastic network of filamentary cholesteric domains that stabilizes the planar CLC texture reached in an electric field. In turn, the reversible mode corresponds to the unwound cholesteric state. Potential applications of this effect are discussed.

Stereochemical Control of Nonamphiphilic Lyotropic Liquid Crystals: Chiral Nematic Phase of Assemblies Separated by Six Nanometers of Aqueous Solvents

Unlike conventional thermotropic and lyotropic liquid crystals, nonamphiphilic lyotropic liquid crystals consist of hydrated assemblies of nonamphiphilic molecules that are aligned with a separation of about 6 nm between assemblies in an aqueous environment. This separation raises the question of how chirality, either from chiral mesogens or chiral dopants, would impact the phase as the assemblies that need to interact with each other are about 6 nm apart. Here, we report the synthesis of three stereoisomers of disodium chromonyl carboxylate, 5'DSCG-diviol, and the correlation between the molecular structure, bulk assembly, and liquid crystal formation. We observed that the chiral isomers (enantiomers 5'DSCG-(R,R)-diviol and 5'DSCG-(S,S)-diviol) formed liquid crystals while the achiral isomer 5'DSCG-meso-diviol did not. Circular dichroism indicated a chiral conformation with bisignate cotton effect. The nuclear Overhauser effect in proton NMR spectroscopy revealed conformations that are responsible for liquid crystal formation. Cryogenic transmission electron microscopy showed that chiral 5'DSCG-diviols form assemblies with crossings. Interestingly, only planar alignment of the chiral nematic phase was observed in liquid crystal cells with thin spacers. The homeotropic alignment that permitted a fingerprint texture was obtained only when the thickness of the liquid crystal cell was increase to above ~500 μm. These studies suggest that hydrated assemblies of chiral 5'DSCG-diviol can interact with each other across a 6 nm separation in an aqueous environment by having a twist angle of about 0.22° throughout the sample between the neighboring assemblies.

Rheology of Nanocrystalline Cellulose Aqueous Suspensions

The rheological properties and microstructure of nanocrystalline cellulose (NCC) aqueous suspensions have been investigated at different concentrations. The suspension is isotropic up to 3 wt %, and phase separates to liquid crystalline and isotropic domains at higher concentrations where the samples exhibit a fingerprint texture and the viscosity profile shows a three-region behavior, typical of liquid crystals. The suspension behaves as a rheological gel at even higher concentrations where the viscosity profile shows a single shear thinning behavior over the whole range of shear rates investigated. The effects of ultrasound energy and temperature on the rheological properties and structure of these suspensions were studied using polarized optical microscopy and rheometry. Our results indicate that the amount of applied ultrasound energy affects the microstructure of the suspensions and the pitch of the chiral nematic domains. The viscosity profile is changed significantly at low shear rates, whereas the viscosity of biphasic suspensions at intermediate and high shear rates decreased with increasing temperature. This suggests that, between 30 and 40 °C, structural rearrangement takes place. At higher concentrations of about 10 wt %, the temperature has no significant effect on viscosity; however, a marked increase in viscosity has been observed at around 50 °C. Finally, the Cox-Merz rule was found to fail after a critical concentration, thereby implying significant structural formation. This critical concentration is much higher for sonicated compared to unsonicated suspensions.

Friction and wear durability studies on the 3D negative fingerprint and honeycomb textured SU-8 surfaces

The effects of two different textures (a 3D negative fingerprint texture and a honeycomb texture) on the tribological performance of SU-8 polymer surface have been investigated with a ball-on-disc tribometer. Friction and wear behaviors of the textured surfaces are conducted against a 4mm diameter silicon nitride (Si3N4) ball counterface. The coefficient of friction for the negative fingerprint textured surface (μ=∼0.08) is much lower than that of the untextured surface (∼0.2) and the honeycomb textured surface (∼0.41) under a normal load of 100mN and a rotational speed of 2rpm. The coefficients of friction of the textured surfaces decrease with increasing normal loads between 100mN and 300mN. Above the normal load of 300mN, the coefficient of friction of the negative fingerprint textured surface increases due to the occurrence of plastic deformation. The honeycomb textured surface has shown the highest coefficient of friction. The wear durability tests are also conducted at a normal load of 100mN and a rotational speed of 500rpm on the untextured/textured surfaces on SU-8 in the presence of an overcoat of a nano-lubricant, perfluoropolyether(PFPE). Six samples i.e. the untextured surface (Si/SU-8 and Si/SU-8/PFPE), the 3D negative fingerprint textured surface (Si/SU-8/FP and Si/SU-8/FP/PFPE) and the honeycomb textured surface (Si/SU-8/HC and Si/SU-8/HC/PFPE), each with and without PFPE nano-lubricant, have been investigated for their tribological behaviours. The negative fingerprint pattern on SU-8 with PFPE coating has shown the highest wear life of 60,000 cycles under a normal load of 100mN. The reasons for excellent tribological performance of 3D fingerprinted SU-8 surface are analyzed using the Hertzian contact area calculation.

Biometric cryptosystem based on discretized fingerprint texture descriptors

This paper focuses on a biometric cryptosystem implementation and evaluation based on a number of fingerprint texture descriptors. The texture descriptors, namely, the Gabor filter-based FingerCode, a local binary pattern (LBP), and a local direction pattern (LDP), and their various combinations are considered. These fingerprint texture descriptors are binarized using a biometric discretization method and used in a fuzzy commitment scheme (FCS). We constructed the biometric cryptosystems, which achieve a good performance, by fusing discretized fingerprint texture descriptors and using effective error-correcting codes. We tested the proposed system on a FVC2000 DB2a fingerprint database, and the results demonstrate that the new system significantly improves the performance of the FCS for texture-based fingerprints.

Preparation, characterization and cytocompatibility of polyurethane/cellulose based liquid crystal composite membranes

Two types of polyurethane/liquid crystal (PU/LC) composite membranes with different LC contents, namely polyurethane/octyl hydroxypropyl cellulose ester (PU/OPC) and polyurethane/propyl hydroxypropyl cellulose ester (PU/PPC), were prepared and studied. The effects of surface properties on cell compatibility of the membranes were elucidated. PPC tended to assemble to independent phases in the composite membranes, while OPC formed uniformly distributed LC domains. As the introduction of LC, phase separation occurred, and the crystallization of PU was disrupted. The surface of PU/LC composite membranes showed fingerprint texture and two-phase morphology. Hydrophilicity of the two types of composite membranes exhibited a reversal tendency with the increase of LC contents. Cells seeded on the composite membranes presented favorable growth when the content of LC was over 30%, especially on PU/OPC complex. The surface morphology, phase separation between LC and PU as well as the type of LC showed significant effects on the cell behaviors.

The effect of different arms on the properties of chiral branched-arm liquid crystals based on isosorbide as the chiral core

A new series of two-arm ( MA1 , MA2 ), four-arm ( MA3 ) and six-arm ( MA4 ) chiral liquid crystalline compounds containing isosorbide as the chiral core were synthesised. Four precursors of branched-arm A1–A4 were first obtained, and then were esterised separately with isosorbide to obtain four chiral branched-arm liquid crystals ( MA1–MA4 ). The structure and properties have been characterised. The results show that MA1 was smectic–cholesteric phase with a fan-like and oily streak texture; MA2–MA4 showed a cholesteric phase with oily streak texture, or lined texture and finger print texture. Isosorbide successfully induced a cholesteric phase. The melting point and clearing point values for MA1–MA4 first increased and then decreased. The branched-arm and chiral core quantity affected the liquid crystalline properties. At the same time, the difference in side-arms resulted in different directions of rotation. MA1–MA2 showed right-handed rotation and had selective reflection; MA3–MA4 demonstrated left-handed rotation and did not have selective reflection.

Optical security device providing fingerprint and designed pattern indicator using fingerprint texture in liquid crystal

An optical security device providing the function of a fingerprint for authentication along with a designed pattern storage function has been proposed. The proposed device uses the random fingerprint texture in the chiral nematic phase of an ultraviolet-curable liquid crystal. Using photopolymerization along with a mask of the designed pattern, a unique pattern can be fixed in the shape of the designed pattern. The random patterns can be used as a fingerprint for such devices. This proposed device has the potential to be an optical security device and an authenticity or information indicator for the user.

Polymer Composites Reinforced by Locking-In a Liquid-Crystalline Assembly of Cellulose Nanocrystallites

An attempt was made to synthesize novel composites comprising poly(2-hydroxyethyl methacrylate) (PHEMA) and cellulose nanocrystallites (CNC) (acid-treated cotton microfibrils) from suspensions of CNC in an aqueous 2-hydroxyethyl methacrylate (HEMA) monomer solution. The starting suspensions (∼5 wt % CNC) separated into an isotropic upper phase and an anisotropic bottom one in the course of quiescent standing. By way of polymerization of HEMA in different phase situations of the suspensions, we obtained films of three polymer composites, PHEMA-CNC(iso), PHEMA-CNC(aniso), and PHEMA-CNC(mix), coming from the isotropic phase, anisotropic phase, and embryonic nonseparating mixture, respectively. All the composites were transparent and, more or less, birefringent under a polarized optical microscope. A fingerprint texture typical of cholesteric liquid crystals of longer pitch spread widely in PHEMA-CNC(aniso) but rather locally appeared in PHEMA-CNC(iso). Any of the CNC incorporations into the PHEMA matrix improved the original thermal and mechanical properties of this amorphous polymer material. In dynamic mechanical measurements, the locking-in of the respective CNC assemblies gave rise to an increase in the glass-state modulus E' of PHEMA as well as a marked suppression of the E'-falling at temperatures higher than T(g) (≈ 110 °C) of the vinyl polymer. It was also observed for the composites that their modulus E' rerose in a range of about 150-190 °C, which was attributable to a secondary cross-linking formation between PHEMA chains mediated by the acidic CNC filler. The mechanical reinforcement effect of the CNC dispersions was ensured in a tensile test, whereby PHEMA-CNC(aniso) was found to surpass the other two composites in stiffness and strength.

Fast Gabor Filterbank and its Application in Fingerprint Texture Analysis

Minutiae-based matching is the main method of fingerprint recognition. Anil K. Jain brought forward a method (FingerCode) which use Gabor filter to extract the texture feature of fingerprint and match it. In order to get a faster algorithm of fingerprint identification, the properties of the real part of Gabor filter are analyzed and the Gabor filter algorithm is accelerated in special conditions and is validated by experiment, which decreases the computational complexity from O(n2) to O(n).

Colloidal particles at the interface between an isotropic liquid and a chiral liquid crystal

We create an interface between a cholesteric liquid crystal (CLC) and an isotropic liquid (silicone oil) at which homeotropic anchoring leads to a well aligned cholesteric layer and the formation of the fingerprint texture. Fluorescent colloidal particles with planar surface anchoring are dispersed in the CLC and subsequently imaged using confocal microscopy. A majority of these particles decorate the interface between the CLC and the silicone oil. We present a detailed study of the position of the particles along the direction perpendicular to the interface: the final distribution of particles perpendicular to the interface has a clear dependence on the ratio between the particle size and the pitch of the CLC. This suggests, supported by simulations, that there is a particle size and pitch length dependent drive to expel particles, due to the elastic energy cost of remaining in the CLC. We use polarizing optical microscopy to observe changes to the fingerprint texture as the particles perturb the interface. This is combined with a qualitative study of the in-plane ordering of the particles. Chains of particles form perpendicular to the helical axis (parallel to the cholesteric layers), whereas disordered aggregates are seen where the direction of the helical axis is not uniform.