Microgel-Guided MXene Assembly for High-Performance, Low-Solid Content Conductive Inks.

Rapid evolution of smart devices necessitates high-performance, lightweight materials for effective electromagnetic interference (EMI) shielding. TiCT MXene nanosheets are promising for such applications, yet the high solid content typically required for 3D-printable MXene inks limits their scalability and cost efficiency. In this study, we present an MXene-based ink with an ultralow solid content (0.

Geometrical impacts of platonic particles on nematic liquid crystal dynamics.

Platonic-solid-like particles in liquid crystals offer intriguing opportunities for engineering complex materials with tailored properties. Inspired by platonic solids' geometric simplicity and symmetry, these particles possess well-defined shapes such as cubes, tetrahedra, octahedra, dodecahedra, and icosahedra. When dispersed within nematic liquid-crystalline media, these particles interact with the surrounding medium in intricate ways, influencing the local orientational order of liquid crystal molecules.

Engineering Nano/Microscale Chiral Self-Assembly in 3D Printed Constructs.

Helical hierarchy found in biomolecules like cellulose, chitin, and collagen underpins the remarkable mechanical strength and vibrant colors observed in living organisms. This study advances the integration of helical/chiral assembly and 3D printing technology, providing precise spatial control over chiral nano/microstructures of rod-shaped colloidal nanoparticles in intricate geometries. We designed reactive chiral inks based on cellulose nanocrystal (CNC) suspensions and acrylamide monomers, enabling the chiral assembly at nano/microscale, beyond the resolution seen in printed materials.

Size-dependent viscoelasticity in hybrid colloidal gels based on spherical soft nanoparticles and two-dimensional nanosilicates of varying size.

Hypothesis: Hetero-aggregation of oppositely charged colloidal particles with controlled architectural and interactional asymmetry allows modifying gel nanostructure and properties. We hypothesize the relative size ratio between cationic nanospheres and varied-size anionic two-dimensional nanoclays will influence the gel formation mechanisms and resulting rheological performance.

Experiments: Hybrid colloidal gels formed via hetero-aggregation of cationic gelatin nanospheres (∼400 nm diameter) and five types of nanoclays with similar 1 nm thickness but different lateral sizes ranging from ∼ 30 nm to ∼ 3000 nm.

Photonic features of blue phase liquid crystals under curved confinement.

Blue phase (BP) liquid crystals represent a fascinating state of soft matter that showcases unique optical and electro-optical properties. Existing between chiral nematic and isotropic phases, BPs are characterized by a three-dimensional cubic lattice structure resulting in selective Bragg reflections of light and consequent vivid structural colors. However, the practical realization of these material systems is hampered by their narrow thermal stability and multi-domain crystalline nature.

3D printing of responsive chiral photonic nanostructures.

Finely controlled flow forces in extrusion-based additive manufacturing can be exploited to program the self-assembly of malleable nanostructures in soft materials by integrating bottom-up design into a top-down processing approach. Here, we leverage the processing parameters offered by direct ink-writing (DIW) to reconfigure the photonic chiral nematic liquid crystalline phase in hydroxypropyl cellulose (HPC) solutions prior to deposition on the writing substrate to direct structural evolution from a particular initial condition. Moreover, we incorporate polyethylene glycol (PEG) into iridescent HPC inks to form a physically cross-linked network capable of inducing kinetic arrest of the cholesteric/chiral pitch at length scales that selectively reflect light throughout the visible spectrum.

3D Printing-Assisted Self-Assembly to Bio-Inspired Bouligand Nanostructures.

Architected materials with nano/microscale orders can provide superior mechanical properties; however, reproducing such levels of ordering in complex structures has remained challenging. Inspired by Bouligand structures in nature, here, 3D printing of complex geometries with guided long-order radially twisted chiral hierarchy, using cellulose nanocrystals (CNC)-based inks is presented. Detailed rheological measurements, in situ flow analysis, polarized optical microscopy (POM), and director field analysis are employed to evaluate the chiral assembly over the printing process.

Director Distortion and Phase Modulation in Deformable Nematic and Smectic Liquid Crystal Spheroids.

The growing interest in integrating liquid crystals (LCs) into flexible and miniaturized technologies brings about the need to understand the interplay between spatially curved geometry, surface anchoring, and the order associated with these materials. Here, we integrate experimental methods and computational simulations to explore the competition between surface-induced orientation and the effects of deformable curved boundaries in uniaxially and biaxially stretched nematic and smectic microdroplets. We find that the director field of the nematic LCs upon uniaxial strain reorients and forms a larger twisted defect ring to adjust to the new deformed geometry of the stretched droplet.

Tuning the Self-Assembled Morphology of TiCT MXene-Based Hybrids for High-Performance Electromagnetic Interference Shielding.

Hybrid materials based on transition metal carbide and nitride (MXene) nanosheets have great potential for electromagnetic interference (EMI) shielding due to their excellent electrical conductivity. However, the performance of final products depends not only on the properties of constituent components but also on the morphology of the assembly. Here, via the controlled diffusion of positively charged poly(allylamine hydrochloride) (PAH) chains into the negatively charged TiCT MXene suspension, MXene/PAH hybrids in the forms of thin films, porous structures, and fibers with distinguished internal morphologies are obtained.

Elastic Instability of Cubic Blue Phase Nano Crystals in Curved Shells.

Many crystallization processes, including biomineralization and ice-freezing, occur in small and curved volumes, where surface curvature can strain the crystal, leading to unusual configurations and defect formation. The role of curvature on crystallization, however, remains poorly understood. Here, we study the crystallization of blue phase (BP) liquid crystals under curved confinement, which provides insights into the mechanism by which BPs reconfigure their three-dimensional lattice structure to adapt to curvature.

Hybrid colloidal gels with tunable elasticity formed by charge-driven assembly between spherical soft nanoparticles and discotic nanosilicates.

Colloidal gels based on electrostatic interparticle attractions hold unexploited potential for tailoring their microstructure and properties. Here, we demonstrate that hetero-aggregation between oppositely charged particles with different geometries is a viable strategy for controlling their properties. Specifically, we studied hybrid colloidal gels prepared by the charge-driven assembly of oppositely charged spherical gelatin nanoparticles and two-dimensional (2D) nanosilicates.

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.

Control of Monodomain Polymer-Stabilized Cuboidal Nanocrystals of Chiral Nematics by Confinement.

Liquid crystals are important components of optical technologies. Cuboidal crystals consisting of chiral liquid crystals-the so-called blue phases (BPs), are of particular interest due to their crystalline structures and fast response times, but it is critical that control be gained over their phase behavior as well as the underlying dislocations and grain boundaries that arise in such systems. Blue phases exhibit cubic crystalline symmetries with lattice parameters in the 100 nm range and a network of disclination lines that can be polymerized to widen the range of temperatures over which they occur.

Prolate and oblate chiral liquid crystal spheroids.

Liquid crystals are known to exhibit intriguing textures and color patterns, with applications in display and optical technologies. This work focuses on chiral materials and examines the palette of morphologies that arises when microdroplets are deformed into nonspherical shapes in a controllable manner. Specifically, geometrical confinement and mechanical strain are used to manipulate orientational order, phase transitions, and topological defects that arise in chiral liquid crystal droplets.

A pH-Triggered, Self-Assembled, and Bioprintable Hybrid Hydrogel Scaffold for Mesenchymal Stem Cell Based Bone Tissue Engineering.

Effective bone tissue engineering can restore bone and skeletal functions that are impaired by traumas and/or certain medical conditions. Bone is a complex tissue and functions through orchestrated interactions between cells, biomechanical forces, and biofactors. To identify ideal scaffold materials for effective mesenchymal stem cell (MSC)-based bone tissue regeneration, here we develop and characterize a composite nanoparticle hydrogel by combining carboxymethyl chitosan (CMCh) and amorphous calcium phosphate (ACP) (designated as CMCh-ACP hydrogel).

Water Flux Induced Reorientation of Liquid Crystals.

It is well understood that the adsorption of solutes at the interface between a bulk liquid crystal phase and an aqueous phase can lead to orientational or anchoring transitions. A different principle is introduced here, whereby a transient reorientation of a thermotropic liquid crystal is triggered by a spontaneous flux of water across the interface. A critical water flux can be generated by the addition of an electrolyte to the bulk aqueous phase, leading to a change in the solvent activity; water is then transported through the liquid crystal phase and across the interface.

Mesoscale martensitic transformation in single crystals of topological defects.

Liquid-crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of double-twisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by the existence of grain boundaries between randomly oriented crystalline nanodomains.

Gelatin-Derived Graphene-Silicate Hybrid Materials Are Biocompatible and Synergistically Promote BMP9-Induced Osteogenic Differentiation of Mesenchymal Stem Cells.

Graphene-based materials are used in many fields but have found only limited applications in biomedicine, including bone tissue engineering. Here, we demonstrate that novel hybrid materials consisting of gelatin-derived graphene and silicate nanosheets of Laponite (GL) are biocompatible and promote osteogenic differentiation of mesenchymal stem cells (MSCs). Homogeneous cell attachment, long-term proliferation, and osteogenic differentiation of MSCs on a GL-scaffold were confirmed using optical microscopy and scanning electron microscopy.

Molecular Structure of Canonical Liquid Crystal Interfaces.

Numerous applications of liquid crystals rely on control of molecular orientation at an interface. However, little is known about the precise molecular structure of such interfaces. In this work, synchrotron X-ray reflectivity measurements, accompanied by large-scale atomistic molecular dynamics simulations, are used for the first time to reconstruct the air-liquid crystal interface of a nematic material, namely, 4-pentyl-4'-cyanobiphenyl (5CB).

Understanding Atomic-Scale Behavior of Liquid Crystals at Aqueous Interfaces.

The ordered environment presented by liquid crystals at interfaces enables a range of novel functionalities that is only now beginning to be exploited in applications ranging from light focusing devices to biosensors. One key feature of liquid crystals is that molecular events occurring at an interface propagate over large distances through the bulk. In spite of their importance, our fundamental understanding of liquid crystal-water and liquid crystal-air interfaces remains limited.

Mesoscale structure of chiral nematic shells.

There is considerable interest in understanding and controlling topological defects in nematic liquid crystals (LCs). Confinement, in the form of droplets, has been particularly effective in that regard. Here, we employ a Landau-de Gennes formalism to explore the geometrical frustration of nematic order in shell geometries, and focus on chiral materials.

Glass-like dynamics in the cell and in cellular collectives.

Prominent fluctuations, heterogeneity, and cooperativity dominate the dynamics of the cytoskeleton as well as the dynamics of the cellular collective. Such systems are out of equilibrium, disordered, and remain poorly understood. To explain these findings, we consider a unifying mechanistic rubric that imagines these systems as comprising phases of soft condensed matter in proximity to a glass or jamming transition, with associated transitions between solid-like versus liquid-like phases.