Birefringence Patterns Research Articles

Dynamic Photoelastic Analysis of Stress Distribution in Simulated Canals Using Rotary Instruments with Varied Tip and Taper Sizes: A Quasi-3D Approach

IntroductionTo compare the stress produced on the walls of simulated canals by rotary instruments with varied tip and taper sizes. MethodsNinety isotropic transparent blocks, each containing a 60-degree curved canal, were distributed into 18 groups (n = 5) based on the instrument tip (sizes 10, 15, 20, 25, 30, and 35) and taper (sizes 0.02, 0.04, and 0.06). The blocks were fixed in a circular polariscope setup for dark field analysis. A digital camera was employed to capture the real-time birefringence patterns generated by each instrument. Digital image frames, corresponding to the instrument reaching the end of each canal third, were extracted and evaluated by 2 independent observers for the stress generation on canal walls. The data analysis employed a semi-quantitative scale ranging from 0 to 5. Cohen's Kappa coefficient test was used to determine the inter-observer agreement while the results were compared using Kruskal–Wallis test followed by an all-pairwise posthoc procedure (α = 5%). ResultsInter-observer agreement was 0.95. A significant influence of the tip size on stress was observed across the coronal (P = .011), middle (P = .006), and apical (P = .026) thirds. In contrast, taper size did not affect the stress induced at the coronal (P = .509), middle (P = .958), or apical (P = .493) thirds. The variations in tip and taper sizes did not result in a significant stress differences among the thirds (P = .181). ConclusionsThe stress significantly increased across all canal thirds with larger tip sizes of rotary instruments, whereas the taper sizes did not influence the stress when compared to the canal thirds.

Mitigation of BMP-induced inflammation in craniofacial bone regeneration and improvement of bone parameters by dietary hesperidin

Based on anti-inflammatory and osteogenic properties of hesperidin (HE), we hypothesized its systemic administration could be a cost-effective method of improving BMP-induced bone regeneration. Sprague–Dawley rats were allocated into 4 groups (n = 10/group): a 5-mm critical-sized mandible defect + collagen scaffold or, scaffold + 1 µg of BMP2 with and without dietary HE at 100 mg/kg. HE was administered by oral gavage 4 weeks prior to surgeries until euthanasia at day 7 or 14 post-surgery. The healing tissue within the defect collected at day 7 was subjected to gene expression analysis. Mandibles harvested at day 14 were subjected to microcomputed tomography and histology. HE + BMP2-treated rats had a statistically significant decrease in expression of inflammatory genes compared to BMP2 alone. The high-dose BMP2 alone caused cystic-like regeneration with incomplete defect closure. HE + BMP2 showed virtually complete bone fusion. Collagen fibril birefringence pattern (red color) under polarized light indicated high organization in BMP2-induced newly formed bone (NFB) in HE-supplemented group (p < 0.05). Clear changes in osteocyte lacunae as well as a statistically significant increase in osteoclasts were found around NFB in HE-treated rats. A significant increase in trabecular volume and thickness, and trabecular and cortical density was found in femurs of HE-supplemented rats (p < 0.05). Our findings show, for the first time, that dietary HE has a remarkable modulatory role in the function of locally delivered high-dose BMP2 in bone regeneration possibly via control of inflammation, osteogenesis, changes in osteocyte and osteoclast function and collagen maturation in regenerated and native bone. In conclusion, HE had a significant skeletal bone sparing effect and the ability to provide a more effective BMP-induced craniofacial regeneration.

Preparation and Characterization of PVA/ CNC/ ε-Polylysine Biocomposites for Potential Food Packaging Application

In recent years, there has been an increasing focus on creating sustainable and biodegradable materials for use in food packaging. The purpose of this study is to examine the impact of incorporating Cellulose Nanocrystals (CNC)/ε-Polylysine (ε-PL) additives into a Polyvinyl Alcohol (PVA) matrix for food packaging. Different filler concentrations and PVA/ε-PL ratios (5:0.3 wt%), (5:0.6 wt.%), and (5:0.9 wt.%) were used to produce the PVA/CNC/ε -PL nanocomposite films through solvent casting. Additionally, PVA and PVA/CNC were prepared for control purposes. The thin film samples were then characterized using a visual inspection, thickness, optical microscopy, FTIR-ATR and XRD. Visual inspection of the nanocomposite films against the logo showed that the increasing weight ratio of CNC/ε-PL did not significantly affect the transparency of the nanocomposites, while those under the polarized optical microscopy exhibited the birefringent patterns observed in the samples with CNC. The FTIR-ATR analysis of the nanocomposite films revealed the functional groups associated with the PVA, CNC, ε-PL, and the mixtures are consistent. The tensile test demonstrated a substantial enhancement in the presence of CNC and CNC/ε-PL. In summary, the PVA/CNC/ε-PL nanocomposites present a promising potential as biodegradable materials for food packaging applications.

Liquid crystal-based label-free low-cost sensing platform: Engineering design based on interfacial interaction and transport phenomena

Typically, the detection methods of chemical species in sensing platform involves the use of labelling agents. Even though it is selective, the process is complex and time consuming. Liquid crystals (LC) are sensitive and rapidly responsive to the presence of any foreign species. When a LC layer interacts with aqueous (ionic surfactant) solution, there is homeotropic alignment of the director orientation due to the anisotropic interactions at the interface. This leads to the dark birefringence patterns observed in polarised microscope under cross polarisation. In the presence of H+ in the aqueous layer, the LC orientation is distorted resulting in a change of the birefringence patterns in the polarised micrographs. We have prepared an optical cell where the aqueous solution can interact with the LC layer confined within micrometre sized grids. The flow arrangement and the associated mass transfer process is optimised for enhanced interaction. The elastic interactions of the LC layer with H+ at the interface distorts the director orientation, and the birefringence pattern is captured with polarised microscope (cross-polarisation). There is a correlation between the polarised micrographs and the concentration of the H+, which forms the basis of detection principle. The detection of H+ has no interference with salts. The present method can be used for recognition of (bio-) chemical reactions releasing H+. The developed optical flow cell is inexpensive, less than $1. The outcome of the present work may be useful for technological adaption and prospective use in point-of-care devices and field test kits.

Iridescent Features Correlating with Periodic Assemblies in Custom-Crystallized Arylate Polyesters

In this study, five different aryl polyesters, i.e., poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), poly(octamethylene terephthalate) (POT), poly(nonamethylene terephthalate) (PNT), and poly(decamethylene terephthalate) (PDT), upon crystallization at a suitable temperature range, all exhibit ring-banded spherulites with universal characteristics. Previous research has revealed some fundamental mechanisms underlying the formation of periodic hierarchical structures. Additionally, this study further explored correlations among micro/nanocrystal assemblies in the top surface and internal grating architectures and the structural iridescent properties. The interior lamellar assembly of arylate polyesters’ banded spherulites is shown to exhibit periodic birefringence patterns that are highly reminiscent of those found in a variety of biological structures, with the capacity for iridescence from light interference. A laser diffraction analysis was also used to support confirmation of this condition, which could result in an arc diffraction pattern indicative of the presence of ringed spherulites. Among the five arylate polyesters, only PET is incapable of regularly producing ring-banded morphology, and thus cannot produce any iridescent color.

Decoding Optical Responses of Contact-Printed Arrays of Thermotropic Liquid Crystals Using Machine Learning: Detection and Reporting of Aqueous Amphiphiles with Enhanced Sensitivity and Selectivity.

Surfactants and other amphiphilic molecules are used extensively in household products, industrial processes, and biological applications and are also common environmental contaminants; as such, methods that can detect, sense, or quantify them are of great practical relevance. Aqueous emulsions of thermotropic liquid crystals (LCs) can exhibit distinctive optical responses in the presence of surfactants and have thus emerged as sensitive, rapid, and inexpensive sensors or reporters of environmental amphiphiles. However, many existing LC-in-water emulsions require the use of complicated or expensive instrumentation for quantitative characterization owing to variations in optical responses among individual LC droplets. In many cases, the responses of LC droplets are also analyzed by human inspection, which can miss subtle color or topological changes encoded in LC birefringence patterns. Here, we report an LC-based surfactant sensing platform that takes a step toward addressing several of these issues and can reliably predict concentrations and types of surfactants in aqueous solutions. Our approach uses surface-immobilized, microcontact-printed arrays of micrometer-scale droplets of thermotropic LCs and hierarchical convolutional neural networks (CNNs) to automatically extract and decode rich information about topological defects and color patterns available in optical micrographs of LC droplets to classify and quantify adsorbed surfactants. In addition, we report computational capabilities to determine relevant optical features extracted by the CNN from LC micrographs, which can provide insights into surfactant adsorption phenomena at LC-water interfaces. Overall, the combination of microcontact-printed LC arrays and machine learning provides a convenient and robust platform that could prove useful for developing high-throughput sensors for on-site testing of environmentally or biologically relevant amphiphiles.

Voxelated opto-physically unclonable functions via irreplicable wrinkles

The increased prevalence of the Internet of Things (IoT) and the integration of digital technology into our daily lives have given rise to heightened security risks and the need for more robust security measures. In response to these challenges, physical unclonable functions (PUFs) have emerged as promising solution, offering a highly secure method to generate unpredictable and unique random digital values by leveraging inherent physical characteristics. However, traditional PUFs implementations often require complex hardware and circuitry, which can add to the cost and complexity of the system. We present a novel approach using a random wrinkles PUF (rw-PUF) based on an optically anisotropic, facile, simple, and cost-effective material. These wrinkles contain randomly oriented liquid crystal molecules, resulting in a two-dimensional retardation map corresponding to a complex birefringence pattern. Additionally, our proposed technique allows for customization based on specific requirements using a spatial light modulator, enabling fast fabrication. The random wrinkles PUF has the capability to store multiple data sets within a single PUF without the need for physical alterations. Furthermore, we introduce a concept called ‘polyhedron authentication,’ which utilizes three-dimensional information storage in a voxelated random wrinkles PUF. This approach demonstrates the feasibility of implementing high-level security technology by leveraging the unique properties of the rw-PUF.

Testing charge quantization with axion string-induced cosmic birefringence

We demonstrate that the Peccei-Quinn-electromagnetic anomaly coefficient 𝒜 can be directly measured from axion string-induced cosmic birefringence by applying scattering transform to the anisotropic polarization rotation of the cosmic microwave background. This breaks the degeneracy between 𝒜 and the effective number of string loops in traditional inference analyses that are solely based on the spatial power spectrum of polarization rotation. Carrying out likelihood-based parameter inference on mock rotation realizations generated according to phenomenological string network models, we show that scattering transform is able to extract enough non-Gaussian information to clearly distinguish a number of discrete 𝒜 values, for instance 𝒜=1/9, 1/3, 2/3, in the ideal case of noise-free rotation reconstruction, and, to a lesser but interesting degree at reconstruction noise levels comparable to that expected for the proposed CMB-HD concept. In the event of a statistical detection of cosmic birefringence by Stage III or IV CMB experiments, our technique can be applied to test the stringy nature of the birefringence pattern and extract fundamental information about the smallest unit of charge in theories beyond the Standard Model.

A Comparative Evaluation of Collagen in Ameloblastoma and Oral Squamous Cell Carcinoma using Picrosirius Red Staining with Polarizing Microscopy and CD44v6 Immunoreactivity.

Solid multicystic ameloblastoma (SMA) is a locally aggressive, benign odontogenic tumor of odontogenic origin with greater rate of recurrence. Epithelial-mesenchymal interaction plays an important role in tooth morphogenesis that shows complete differentiation of epithelial and ectomesenchymal components to the level of tooth formation. Tumor stroma in ameloblastoma is normal mature collagen that prevents differentiation to the level of tooth formation. Current study evaluates the role of stromal elements in aggressive behavior of SMA using picrosirius red staining with polarizing microscopy and CD44v6 immunohistochemistry (IHC). To compare nature of collagen using picrosirius red staining under polarized microscope and IHC expression of CD44v6 marker in SMA and oral squamous cell carcinoma (OSCC). Thirty blocks were retrieved from departmental archives and subjected to picrosirius red staining and CD44v6 IHC staining. Slides stained with picrosirius red were observed under polarized microscope to report the birefringence pattern. IHC slides were annotated for intensity of staining of tumor cells. In contrast to OSCC's 40% red, 40% yellowish-red, and 20% greenish-yellow birefringence, SMA displayed 87% red, 13% yellowish-red, and 0% greenish-yellow. Compared to OSCC, which had tumor cells stained 9% strongly, 64% moderately, 27% mildly, and 0% negatively, SMA revealed 0% strong, 10% moderate, 60% weak, and 30% negative staining. As opposed to OSCC, which exhibited a greater quantity of greenish-yellow birefringence of immature collagen, SMA showed predominantly red birefringence, which is suggestive of mature collagen with a lack of metastasis. Comparing SMA to OSCC, the lack of significant CD44v6 positivity suggests that there has not been perineural invasion or regional metastases in SMA.

Birefringence properties of human immotile spermatozoa and ICSI outcome

Research questionIn sperm samples with complete asthenozoospermia, pregnancies are achieved by intracytoplasmic sperm injection (ICSI), but this condition has a negative impact on fertilization and embryo development owing to the difficulty of identifying viable cells for oocyte injection. Is the selection of sperm cells with head birefringence properties under polarizing light a successful strategy to identify viable spermatozoa? DesignThis study included 192 ICSI cycles with complete asthenozoospermia (83 ejaculated and 109 testicular samples) performed under polarized light. Two types of sperm head birefringence were distinguished: partial (presumably reacted spermatozoa) and total (presumably intact acrosome). In some sperm cells, no birefringence was present. The main outcome of the study was the cumulative live birth rate (cLBR) per ICSI cycle. ResultsSeventy-three deliveries resulted with 38.0% cLBR per ICSI cycle. The injection of birefringent spermatozoa led to significantly higher rates of fertilization, embryo development and implantation compared with the absence of birefringence (P < 0.001). Similarly, the resulting cLBR were 53.6% and 9.0%, respectively (P < 0.001). Spermatozoa with partial head birefringence yielded significantly higher fertilization and embryo utilization rates compared with total birefringence. The cLBR showed the same trend (62.7% and 46.7%, respectively, P = 0.048). Multiple logistic regression analysis showed the pattern of partial birefringence to be strongly associated with live birth rate. ConclusionsImmotile sperm cells with birefringence properties under polarized light have higher chances of inducing fertilization and embryo development compared with non-birefringent cells. In addition, a pattern of partial birefringence, associated with a reacted acrosome, is the strongest predictive factor for live birth delivery, both in ejaculated and testicular samples.

Corresponding relationship between characteristic birefringence, strain, and impurities in Zimbabwean mixed-habit diamonds revealed by mapping techniques

Abstract. Birefringence in diamond is an optical phenomenon related to strain and various defects in crystal lattices. Despite extensive investigations being done to characterize and quantify it, there is still controversy about its origin in diamond lattices. Here we report the relationship between the distribution of birefringence patterns observed under cross-polarized light, strain features analyzed by Raman mapping, and the impurity characteristics revealed by Fourier transform infrared spectroscopy (FTIR) mapping in natural mixed-habit diamonds. It was deduced that the plastic deformation was enhanced with higher tensile residual stress, and nitrogen and VN3H defects were more enriched as a result of the temperature increase during crystallization, at growth bands showing straight birefringence patterns and the relative enrichment of graphite inclusions. These results provided solid data and insights for birefringence-related properties in diamond and correlated the occurrence of birefringence with diamond spectroscopic properties, which promoted the understanding of the formation of birefringence in natural diamonds and would be helpful for the synthesis of high-quality, birefringence-free diamonds.

Dynamic and Static Assembly of Sulfated Cellulose Nanocrystals with Alkali Metal Counter Cations.

Sulfate groups on cellulose particles such as cellulose nanocrystals (CNCs) provide colloidal stability credit to electrostatic repulsion between the like-charged particles. The introduction of sodium counter cations on the sulfate groups enables drying of the CNC suspensions without irreversible aggregation. Less is known about the effect of other counter cations than sodium on extending the properties of the CNC particles. Here, we introduce the alkali metal counter cations, Li+, Na+, K+, Rb+, and Cs+, on sulfated CNCs without an ion exchange resin, which, so far, has been a common practice. We demonstrate that the facile ion exchange is an efficient method to exchange to any alkali metal cation of sulfate half esters, with exchange rates between 76 and 89%. The ability to form liquid crystalline order in rest was observed by the presence of birefringence patterns and followed the Hofmeister series prediction of a decreasing ability to form anisotropy with an increasing element number. However, we observed the K-CNC rheology and birefringence as a stand-out case within the series of alkali metal modifications, with dynamic moduli and loss tangent indicating a network disruptive effect compared to the other counter cations, whereas observation of the development of birefringence patterns in flow showed the absence of self- or dynamically-assembled liquid crystalline order.

Programmable Birefringent Patterns from Modulating the Localized Orientation of Cellulose Nanocrystals.

Birefringence has been attracting broad attention due to its strong potential for applications in biomedicine and optics, such as biomedical diagnosis, colorimetric sensing, retardant, and polarization encoding. However, engineering architectures with precisely controllable birefringence remains a challenge due to the lack of effective modulation of the localized orientation. Here, by taking advantage of the inherently one-dimensional (1D) anisotropic structure of cellulose nanocrystals (CNCs), we demonstrate an approach to tune the alignment of CNCs with a well-controllable orientation at localized preciseness, which is in contrast to the previously reported unidirectional/radical orientation of CNC-based birefringent structures. The localized modulation of CNC orientation is facilitated by directing the 1D nanocrystals to align along the template periphery and the migrated three-phase contact line during the evaporation. The resultant CNC films exhibit birefringent extinction patterns under polarized light, in which versatile pattern designs can be obtained by employing templates with different shapes and template arrays with varied layouts. Due to the locally modulated orientation of CNCs, the films indicate "kaleidoscope-like" dynamically transformable designs of the birefringent patterns depending on the polarized angle, which has barely been observed previously. Furthermore, an N-nary encoding system for abundant information storage is demonstrated based on the sunlight-transparent CNC films, but with visible extinction patterns under polarized light, which is promising for encryptions, anticounterfeiting, and imaging, enriching the attractive research area of bio-based photonics.

Magneto-Orientation of Magnetic Double Stacks for Patterned Anisotropic Hydrogels with Multiple Responses and Modulable Motions.

Reported here is a multi‐response anisotropic poly(N‐isopropylacrylamide) hydrogel developed by using a rotating magnetic field to align magnetic double stacks (MDSs) that are fixed by polymerization. The magneto‐orientation of MDSs originates from the unique structure with γ‐Fe2O3 nanoparticles sandwiched by two silicate nanosheets. The resultant gels not only exhibit anisotropic optical and mechanical properties but also show anisotropic responses to temperature and light. Gels with complex ordered structures of MDSs are further devised by multi‐step magnetic orientation and photolithographic polymerization. These gels show varied birefringence patterns with potentials as information materials, and can deform into specific configurations upon stimulations. Multi‐gait motions are further realized in the patterned gel through dynamic deformation under spatiotemporal light and friction regulation by imposed magnetic force. The magneto‐orientation assisted fabrication of hydrogels with anisotropic structures and additional functions should bring opportunities for gel materials in biomedical devices, soft actuators/robots, etc.

Magneto‐Orientation of Magnetic Double Stacks for Patterned Anisotropic Hydrogels with Multiple Responses and Modulable Motions

AbstractReported here is a multi‐response anisotropic poly(N‐isopropylacrylamide) hydrogel developed by using a rotating magnetic field to align magnetic double stacks (MDSs) that are fixed by polymerization. The magneto‐orientation of MDSs originates from the unique structure with γ‐Fe2O3 nanoparticles sandwiched by two silicate nanosheets. The resultant gels not only exhibit anisotropic optical and mechanical properties but also show anisotropic responses to temperature and light. Gels with complex ordered structures of MDSs are further devised by multi‐step magnetic orientation and photolithographic polymerization. These gels show varied birefringence patterns with potentials as information materials, and can deform into specific configurations upon stimulations. Multi‐gait motions are further realized in the patterned gel through dynamic deformation under spatiotemporal light and friction regulation by imposed magnetic force. The magneto‐orientation assisted fabrication of hydrogels with anisotropic structures and additional functions should bring opportunities for gel materials in biomedical devices, soft actuators/robots, etc.

Stabilized director buckling patterns in nematic elastomers and their dynamic optical effects

AbstractPearlescence and iridescence, which are a class of light diffusion effects that exhibit sharp viewing-angle-dependent brightness and colors, are important material properties for notification purposes and lighting devices. Here we report elastomeric materials with self-organized periodic birefringent patterns that exhibit these optical effects, with additional dynamic and reversible tunability. A stack of micron-thick layers, each of which has a nematic director tilted from the layer normal in a different direction, assembles a birefringence-pattern-based anisotropic diffuser in a nematic liquid-crystal elastomer. The periodic pattern is formed after buckling induced by the uniaxial thermal shrinkage, and the associated rotation of an initially uniform director state. The patterns can be stabilized by secondary crosslinking. Upon deformation or increasing the temperature, the light diffusion with viewing-angle-dependent colors reversibly fades owing to the diminishing of optical effects via strain-induced alignment or thermal randomization of birefringence, respectively. Such elastomers with tunable self-organized birefringence patterns can be used for reconfigurable optical elements and strain/temperature detection in the form of films, tapes, rods, and fibers.

Ultrasonic Anisotropy in Composites: Effects and Applications

Stiffness anisotropy is a natural consequence of a fibrous structure of composite materials. The effect of anisotropy can be two-fold: it is highly desirable in some cases to assure a proper material response, while it might be even harmful for the applications based on “isotropic” composite materials. To provide a controllable flexibility in material architecture by corresponding fibre alignment, the methodologies for the precise non-destructive evaluation of elastic anisotropy and the fibre orientation are required. The tasks of monitoring the anisotropy and assessing the fibre fields in composites are analyzed by using the two types of ultrasonic waves suitable for regular plate-shaped composite profiles. In the plate wave approach, the effect of “dispersion of anisotropy” has been shown to make the wave velocity anisotropy to be a function of frequency. As a result, the in-plane velocity pattern measured at a certain frequency is affected by the difference in the wave structure, which activates different elasticity against the background of intrinsic material anisotropy. Phase velocity anisotropy and its frequency dependence provide a frequency variation of the beam steering angle for plate waves (dispersion of beam steering). In strongly anisotropic composite materials, the beam steering effect is shown to provide a strong focusing of ultrasonic energy (phonon focusing). For bulk shear waves, the orthotropic composite anisotropy causes the effect of acoustic birefringence. The birefringent acoustic field provides information on stiffness anisotropy which can be caused by internal stresses, texture, molecular or/and fibre orientation. On this basis, a simple experimental technique is developed and applied for mapping of fibre orientation in composite materials. Various modes of acoustic birefringence are analyzed and applied to assessing the fibre fields in injection moulding composites and to identify the fibre lay-ups in multiply materials. The birefringence pattern is also shown to be sensitive and applicable to characterizing impact- and mechanical stress-induced damage in composites.

Polymerizable channel-like stacks derived from cyclic tetrameric diacetylenes

A small series of cyclic diacetylenes has been synthesized and tested by scanning electron microscopy (SEM), single crystal X-ray diffraction, and atomic force microscopy (AFM) to examine their ability to form arrangements of discrete molecules in the solid state. Examining solid state structures clearly demonstrated propensity of diacetylene tetramers to form channel-like stacks. Remarkably, cyclotetradiyne DA-4 monomer tends to produce two types of nano-tubular motifs (i.e., the channel-like arrangement with solvent matrix inside and unprecedented flattened nano-tube incorporated no solvent guest molecules) which is indicative of the weak C–H/π interactions dominating and directing the stacking in such simplistic diacetylene cyclic systems. Noteworthy, DA-4 molecules may be crystallized from organic solvents into birefringent branchy patterns revealed by Polarized Optical Microscopy (POM) and twisted ribbons of both handedness as evidenced by SEM data. We hypothesize that all these secondary structures may arise from the bundling the individual stacks discovered by single crystal X-ray analysis. Overall, engineering the elongated motifs may open up new opportunities for the future applications such as a rational design of synthetic ion channels and carriers, synthesis of the covalent polymeric nanotubes, etc.

Capillary Flow Characterizations of Chiral Nematic Cellulose Nanocrystal Suspensions.

Studying the flow-induced alignment of anisotropic liquid crystalline materials is of major importance in the 3D printing of advanced architectures. However, in situ characterization and quantitative measurements of local orientations during the 3D printing process are challenging. Here, we report a microfluidic strategy integrated with polarized optical microscopy (POM) to perform the in situ characterization of the alignment of cellulose nanocrystals (CNCs) under the shear-flow condition of the 3D printer's nozzle in the direct ink writing process. To quantify the alignment, we exploited birefringence measurements under white and monochromatic light. We show that the flow-induced birefringence patterns are significantly influenced by the initial structure of the aqueous CNC suspensions. Depending on the CNC concentration and sonication treatment, various structures can form in the CNC suspensions, such as isotropic, chiral nematic (cholesteric), and nematic (gel-like) structures. In the chiral nematic phase, in particular, the shear flow in the microfluidic capillary has a distinct effect on the alignment of the CNC particles. Our experimental results, complemented by hydrodynamic simulations, reveal that at high flow rates (Er ≈ 1000), individual CNC particles align with the flow exhibiting a weak chiral structure. In contrast, at lower flow rates (Er ≈ 241), they display the double-twisted cylinder structure. Understanding the flow effect on the alignment of the chiral liquid crystal can pave the way to designing 3D printed architectures with internal chirality for advanced mechanical and smart photonic applications.

Photoinduced birefringence pattern based on selective induction of photoreactivity with inkjet technology

A random copolymethacrylate containing benzoic acid and benzaldehyde side groups (P1), and a diblock copolymer of P1 and a polymer with heptadecafluorodecyl side groups (P2) were synthesized by means of reversible addition-fragmentation chain transfer (RAFT) polymerization. The linearly polarized (LP) UV light exposure initiated the thermally stimulated photoinduced reorientation of P1(P2)/4-methoxyaniline (AN) films due to the axis-selective photoisomerization of in situ formed N-benzylideneaniline (NBA) groups. A photoinduced birefringent pattern was achieved by sublimation or inkjet coating with AN on the P1(P2) film, which formed NBA moieties in the desired region. Clear birefringent pattern was attained when using P2 because the fluorine-containing block improved the NBA formation at the AN-coated region.