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a) Pluronic F‐127 in cylindrical cross‐section, b) self‐assembled cylinders in a hexagonal 2D lattice with cylinder interdistance, d. c) At rest, the self‐assembled cylinders form microdomains with different orientations. d) Pluronic F‐127 can also form bilayers which are e) self‐assembled in a lamellar structure with interlamellar distance, D. f) They can form extended lamellae or close themselves as multilamellar vesicles. The pink and yellow parts in (a) and (d) corresponds to the hydrophilic and hydrophobic blocks, respectively, in the triblock copolymer. g) Integrated intensity along the azimuthal angle for the hexagonal and lamellar phases of the lyotropic liquid crystals. The insets show the 2D scattering signal recorded by the detector for h) hexagonal and i) lamellar. The anisotropy in the rings shows the orientation of the self‐assembled structure. The highlighted zones for H1 (blue) and Lα (orange) indicate the q‐ranges used for the orientation and angle calculation as well as for the peak fitting analysis.
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Self‐assembled materials such as lyotropic liquid crystals offer a wide variety of structures and applications by tuning the composition. Understanding materials behavior under flow and the induced alignment is wanted in order to tailor structure related properties. A method to visualize the structure and anisotropy of ordered systems in situ under...
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Citations
... As compared with thermotropic liquid crystals, the advantages of microfluidics for characterizing the behavior of lyotropic liquid crystals also attracted attention in the last decade [32,33]. Related research activities are more fundamental and recent and are mostly represented by publications of the last several years [34][35][36][37][38][39], where authors discussed the general aspects of orientation and the phase behavior of confined LLC systems. An interesting feature of LLC in microchannels is that they can be convenient models of biological anisotropic liquids in living capillary systems [40,41]. ...
Lyotropic liquid crystals represent an important class of anisotropic colloid systems. Their integration with optically active nanoparticles can provide us with responsive luminescent media that offer new fundamental and applied solutions for biomedicine. This paper analyzes the molecular-level behavior of such composites represented by tetraethylene glycol monododecyl ether and nanoscale carbon dots in microfluidic channels. Microfluidic confinement allows for simultaneously applying multiple factors, such as flow dynamics, wall effects, and temperature, for the precise control of the molecular arrangement in such composites and their resulting optical properties. The microfluidic behavior of composites was characterized by a set of analytical and modeling tools such as polarized and fluorescent microscopy, dynamic light scattering, and fluorescent spectroscopy, as well as image processing in Matlab. The composites were shown to form tunable anisotropic intermolecular structures in microchannels with several levels of molecular ordering. A predominant lamellar structure of the composites was found to undergo additional ordering with respect to the microchannel axis and walls. Such an alignment was controlled by applying shear and temperature factors to the microfluidic environment. The revealed molecular behavior of the composite may contribute to the synthesis of hybrid organized media capable of polarized luminescence for on-chip diagnostics and biomimetics.
... Spatial characterization techniques such as Raman spectroscopy and x-ray scattering have demonstrated the powerful capability of tracking technique in tailoring structure-related properties. [1][2][3] However, when studying material's structure evolution using Raman spectroscopy and x-ray measurements, reliance on bulk measurements provide only average information about sample properties. 4,5 Furthermore, due to the requirement for high spatial and temporal resolution and precision instruments, [5][6][7] the application of atomic tracking characterizations is still limited. ...
Advanced atomic tracking techniques play a critical role in characterizing structural evolution, elucidating fundamental mechanisms of exotic phenomena and tailoring delicate properties. Thermally driven structural modulation in 2D crystals, such as the charge density wave (CDW), often leads to intriguing quantum properties, making them a valuable platform for exploring fundamental physics and potential device applications. However, despite their significance, experimental studies addressing atomic tracking of thermally‐driven structural evolution in 2D crystals have been limited. Herein, we utilize high‐accuracy variable‐temperature atomic tracking measurements with scanning tunneling microscopy (STM) to directly observe a series of structural transitions in a model 2D crystal, namely NbSe 2 . With the atomic tracking technique, we confirm the existence of the universal thermally‐driven CDW transition hysteresis between the heating and cooling cycles. This transition hysteresis, characterized by a constant temperature offset, represents a new phenomenon of structural evolution. Our findings provide a feasible method to track CDW transitions at the atomic scale in 2D crystals, significantly contributing to a better understanding and the potential modulation of these materials' functions in nanodevices.
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... Scanning S/ WAXS is an imaging method where a focused X-ray beam is used to spatially resolve the scattering of a sample. With this technique, a sample is scanned through the focused beam, collecting a scattering pattern in each scan point in order to derive information on the nanostructure distribution over a sample (Arboleda et al., 2019;Giannini et al., 2014;Rodriguez-Palomo et al., 2021). The methodology is here applied to a partly crystalline solid dispersion of carbamazepine in ethyl cellulose prepared through hot-melt extrusion to demonstrate the capability of spatially resolving the distribution and composition of different phases in the sample and determining the polymorphic form of the drug. ...
A correlative, multiscale imaging methodology for visualising and quantifying the morphology of solid dosage forms by combining ptychographic X-ray computed nanotomography (PXCT) and scanning small- and wide-angle X-ray scattering (S/WAXS) is presented. The methodology presents a workflow for multiscale analysis, where structures are characterised from the nanometre to millimetre regime. Here, the method is demonstrated by characterising a hot-melt extruded, partly crystalline, solid dispersion of carbamazepine in ethyl cellulose. Characterisation of the morphology and solid-state phase of the drug in solid dosage forms is central as this affects the performance of the final formulation. The 3D morphology was visualised at a resolution of 80 nm over an extended volume through PXCT, revealing an oriented structure of crystalline drug domains aligned in the direction of extrusion. Scanning S/WAXS, showed that the nanostructure is similar over the cross section of the extruded filament, with minor radial changes in domain sizes and degree of orientation. The polymorphic forms of carbamazepine were qualified with WAXS, showing a heterogeneous distribution of the metastable forms I and II. This demonstrates the methodology for multiscale structural characterization and imaging to enable a better understanding of the relationships between morphology, performance, and processing conditions of solid dosage forms.
... The effect is most pronounced in the outlet channel due to the elevated shear rates. The finding was confirmed experimentally by Rodriguez-Palomo et al. [55], who found that the order parameter increases downstream of the contraction and associated the phenomenon with an increased shear rate in the smaller channel. The 20 J o u r n a l P r e -p r o o f Journal Pre-proof degree of molecular alignment affects the Leslie angle, which need not be constant in the BE model [46]: ...
Extrusion is an essential element in the production of nematic soft solids, ensuring that the final formulation is sufficiently refined and compacted. The interplay between complex microstructure and processing conditions affects the final product performance and may even lead to material degradation. This paper investigates the flow of nematic liquid crystals in a 4:1 planar contraction as a precursor for material extrusion. We compare two different frameworks for modelling the evolution of the nematic microstructure. The Leslie-Ericksen model represents the liquid crystal microstructure through a lower order (vector) field, where nematic elements are treated as headless rods. We find that the polar nature of the description leads to ambiguity in microstructure orientation on the boundary. As a result, boundary conditions with the same notional interpretation are found to produce significantly varying flow and microstructure distributions. The orientability issue is avoided in the higher-order Beris-Edwards model, where the local orientation and degree of molecular alignment are captured in a single tensor. We find that matching flow and microstructure predictions obtained from both approaches is possible, provided that the boundary orientation is correctly chosen in the Leslie-Ericksen theory. In the lower order framework, a poor choice of boundary condition is found to produce poorer pressure loss predictions in flows through the contraction. The effect is particularly pronounced at low Ericksen numbers, where significant over-prediction of pressure losses can arise.
... It is worth also noting that the flow strains and the employed shear stresses in microfluidics may lead to the alignment of vesicles and affect the orientation of lamellar and hexagonal phases under shear flow, resulting in the appearance of anisotropic SAXS (or SANS) patterns [31,71,74,79]. For instance, a slight alignment was detected during the microfluidic synthesis of MLVs on increasing TFR from 5 to 15 μL/min ( Figure 4A,B). ...
... It is worth also noting that the flow strains and the employed shear stresses in microfluidics may lead to the alignment of vesicles and affect the orientation of lamellar and hexagonal phases under shear flow, resulting in the appearance of anisotropic SAXS (or SANS) patterns [31,71,74,79]. For instance, a slight alignment was detected during the microfluidic synthesis of MLVs on increasing TFR from 5 to 15 µL/min ( Figure 4A,B). ...
... A shear-induced deformation of MLVs was also detected under shear flow during their formation from a lamellar phase [79]. Through a microfluidic SAXS scanning study, Liebi and co-workers [74] reported on the flow-induced transformation of the lamellar (L α ) phase to an aligned lamellae region via MLVs to an extended lamellae region by increasing the shear rates ( Figure 4D). A significant effect of the microfluidic constriction, leading to an orientation of the lamellar phase under flow, was also reported ( Figure 4E,F) in another study [71]. ...
With the ability to cross biological barriers, encapsulate and efficiently deliver drugs and
nucleic acid therapeutics, and protect the loaded cargos from degradation, different soft polymer and lipid nanoparticles (including liposomes, cubosomes, and hexosomes) have received considerable interest in the last three decades as versatile platforms for drug delivery applications and for the design of vaccines. Hard nanocrystals (including gold nanoparticles and quantum dots) are also attractive for use in various biomedical applications. Here, microfluidics provides unique opportunities for the continuous synthesis of these hard and soft nanomaterials with controllable shapes and sizes, and their in situ characterization through manipulation of the flow conditions and coupling to synchrotron small-angle X-ray (SAXS), wide-angle scattering (WAXS), or neutron (SANS) scattering techniques, respectively. Two-dimensional (2D) and three-dimensional (3D) microfluidic devices are attractive not only for the continuous production of monodispersed nanomaterials, but also for improving our understanding of the involved nucleation and growth mechanisms during the formation of hard nanocrystals under confined geometry conditions. They allow further gaining insight into the involved dynamic structural transitions, mechanisms, and kinetics during the generation of self-assembled nanostructures (including drug nanocarriers) at different reaction times (ranging from fractions of seconds to minutes). This review provides an overview of recently developed 2D and 3D microfluidic platforms for the continuous production of nanomaterials, and their simultaneous use in in situ characterization investigations through coupling to nanostructural characterization techniques (e.g., SAXS, WAXS, and SANS).
... Buscema and coworkers [115] employed a contraction device to explore the flow-induced structural changes of liposomes. Very recently, Rodriguez-Palomo et al. [116] employed SAXS to study the structure of lyotropic liquid crystals and their behaviour in contraction microfluidic devices. Few other studies were also reported to explore the flow behaviour of complex fluids in geometries substantially different from the contraction one, including serpentine channels and microfluidic pillars [111,117]. ...
... Integration of such novel methods into existing or new microrheometers can lead to the development of efficient platforms for detailed rheological study, as well as for rapid, order-of-magnitude, estimations of rheological parameters, useful in the medical or industrial practice. [111,111,[113][114][115][116][117][118] Funding: The author acknowledges funding from EPSRC New Investigator Award (Grant EP/S036490/1). ...
The rheological characterisation of liquids finds application in several fields ranging from industrial production to the medical practice. Conventional rheometers are the gold standard for the rheological characterisation; however, they are affected by several limitations, including high costs, large volumes required and difficult integration to other systems. By contrast, microfluidic devices emerged as inexpensive platforms, requiring a little sample to operate and fashioning a very easy integration into other systems. Such advantages have prompted the development of microfluidic devices to measure rheological properties such as viscosity and longest relaxation time, using a finger-prick of volumes. This review highlights some of the microfluidic platforms introduced so far, describing their advantages and limitations, while also offering some prospective for future works.
... The core-shell structure can be explained by a higher local shear rate in the proximities of the walls than in the middle, which significantly influences the viscosity and the orientation parameter in lyotropic liquid crystals [37]. In addition, an apparent wall slip effect could be detected in the liquid crystals in simple shear flow for shear rates above γ = 0.01 s -1 . ...
Extrusion-based 3D printing of hexagonal and lamellar lyotropic liquid crystals is a powerful technique to produce hierarchical materials with well-defined anisotropic structure. Tailoring the properties of 3D printed objects requires a precise control of the nanostructure; however, a sufficiently high degree of anisotropy is often not achieved. In this study, scanning small angle X-ray scattering was performed in situ at the exit of the needle during 3D printing. We study the induced anisotropy and nanostructure in hexagonal and lamellar lyotropic liquid crystals. Mapping of extruded filaments during printing revealed that narrower nozzle diameters (370 μm) resulted in less anisotropic structures with a wider distribution of orientation angles across the cross section, while larger nozzle diameters (550 μm) resulted in more anisotropic structures with an overall higher degree of orientation. The wall shear rate is higher for the narrower nozzle, which produces wall slip, resulting in a highly anisotropic shell, and a less aligned filament core. Further examination of the filaments revealed phase transitions due to solvent evaporation. The time scales were of 10 – 20 min of exposure to atmospheric conditions. Simultaneously, a loss in the macroscopic anisotropy of the hexagonal self-assembled structure was observed. These processes occur during and after extrusion-based 3D printing of liquid crystals and limit the fine control of the final structure. The variability of structures achieved for our different systems highlights the importance of structural characterization during and after extrusion to guarantee high anisotropy and well-defined structures.
Benefiting from the development of high-brilliance synchrotron radiation sources, microbeam X-ray scattering has become a well established scattering-based imaging technology. This article describes the newly constructed time-resolved microbeam small-angle X-ray scattering (µSAXS) experimental station at the BL10U1 beamline at the Shanghai Synchrotron Radiation Facility. The µSAXS endstation provides SAXS/WAXS measurements with a 10 µm hard X-ray beam and a flux of ∼10¹² photons s⁻¹. A multi-axis sample stage, an on-axis viewer and in situ experimental apparatus are incorporated to facilitate multi-method scientific experiments in various material fields. As scientific examples, this article explores 1D tomography, 2D mapping and tomographic sectioning based on X-ray scattering to investigate the micro–nanostructures of polymer fiber, spherulite and bamboo samples.
A gas mixture is introduced into the in situ TEM sample area during gas solid catalysis to monitor the evolution of the surface dynamics of the catalyst and to explore the catalytic mechanism as well.
