Supramolecular bending and twisting in the hierarchical self-assembly of monodisperse mesogenic oligomers.

Understanding how different forms of supramolecular curvature arise during assembly is crucial to designing and tuning the microstructure of hierarchically self-assembled materials. Here, we show that in crystalline phases of mesogenic oligomers, the oligomer length is a critical parameter that determines the type of curvature (Gaussian or cylindrical) exhibited by the self-assembled structures. We use iterative exponential growth to synthesize monodisperse mesogenic oligomers ranging from dimer to octamer.

Evaporation of a Reactive Nanofluid Sessile Drop: .

Mechanisms for surface pattern formation from evaporation of a nanofluid sessile drop are not well understood. In contrast to the coffee-ring effect from inert particles, rapid chemical and morphological transformation of reactive nanoparticles upon rapid evaporative drying are challenging to probe experimentally. Here, using grazing-incidence X-ray surface scattering, the nanostructure of nascent surface patterns has been probed as a ZnO nanofluid sessile drop rapidly dries.

Spatially programmed alignment and actuation in printed liquid crystal elastomers.

Liquid crystal elastomers (LCEs) exhibit reversible shape morphing behavior when cycled above their nematic-to-isotropic transition temperature. During extrusion-based 3D printing, LCE inks are subjected to coupled shear and extensional flows that can be harnessed to spatially control the alignment of their nematic director along prescribed print paths. Here, we combine experiment and modeling to elucidate the effects of ink composition, nozzle geometry, and printing parameters on director alignment.

Programming liquid crystal elastomers for multistep ambidirectional deformability.

Ambidirectionality, which is the ability of structural elements to move beyond a reference state in two opposite directions, is common in nature. However, conventional soft materials are typically limited to a single, unidirectional deformation unless complex hybrid constructs are used. We exploited the combination of mesogen self-assembly, polymer chain elasticity, and polymerization-induced stress to design liquid crystalline elastomers that exhibit two mesophases: chevron smectic C (cSmC) and smectic A (SmA).

Structural maturation of myofilaments in engineered 3D cardiac microtissues characterized using small angle x-ray scattering.

Understanding the structural and functional development of human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) is essential to engineering cardiac tissue that enables pharmaceutical testing, modeling diseases, and designing therapies. Here we use a method not commonly applied to biological materials, small angle x-ray scattering, to characterize the structural development of hiPSC-CMs within three-dimensional engineered tissues during their preliminary stages of maturation. An x-ray scattering experimental method enables the reliable characterization of the cardiomyocyte myofilament spacing with maturation time.

High-density stable glasses formed on soft substrates.

Enabled by surface-mediated equilibration, physical vapour deposition can create high-density stable glasses comparable with liquid-quenched glasses aged for millions of years. Deposition is often performed at various rates and temperatures on rigid substrates to control the glass properties. Here we demonstrate that on soft, rubbery substrates, surface-mediated equilibration is enhanced up to 170 nm away from the interface, forming stable glasses with densities up to 2.

Effects of Erucamide on Fiber "Softness": Linking Single-Fiber Crystal Structure and Mechanical Properties.

Erucamide is known to play a critical role in modifying polymer fiber surface chemistry and morphology. However, its effects on fiber crystallinity and mechanical properties remain to be understood. Here, synchrotron nanofocused X-ray Diffraction (nXRD) revealed a bimodal orientation of the constituent polymer chains aligned along the fiber axis and cross-section, respectively.

Bénard-Marangoni Dendrites upon Evaporation of a Reactive ZnO Nanofluid Droplet: Effect of Substrate Chemistry.

Evaporation of a particle laden sessile drop can lead to complex surface patterns with structural hierarchy. Most commonly, the dispersed particles are inert. We have recently reported that when the sessile drop contains reactive ZnO nanoparticles, solidified Bénard-Marangoni (BM) cells with dendritic micromorphology were formed in the residual surface pattern from in situ-generated nanoclusters.

Dendritic surface patterns from Bénard-Marangoni instabilities upon evaporation of a reactive ZnO nanofluid droplet: A fractal dimension analysis.

We present a box counting fractal dimension (FD) analysis of the dendritic patterns obtained under conditions far from equilibrium via rapid evaporation of a sessile drop containing reactive ZnO nanoparticles. These dendrites were manifestations of solidified Bénard-Marangoni (BM) instability convection cells, and we previously noted that their complex hierarchical morphologies were superficially analogous to the foliage of red algae, Spanish dagger, or spider plant. The fractal dimension of the Bénard-Marangoni dendrites was found to vary in the range of 1.

Hierarchical Surface Patterns upon Evaporation of a ZnO Nanofluid Droplet: Effect of Particle Morphology.

Surface structures with tailored morphologies can be readily delivered by the evaporation-induced self-assembly process. It has been recently demonstrated that ZnO nanorods could undergo rapid chemical and morphological transformation into 3D complex structures of Zn(OH) nanofibers as a droplet of ZnO nanofluid dries on the substrate via a mechanism very different from that observed in the coffee ring effect. Here, we have investigated how the crystallinity and morphology of ZnO nanoparticles would affect the ultimate pattern formation.

Spectroscopic study of ionic liquid adsorption from solution onto gold.

Gold was exposed to ethanol solutions containing 0.1 wt% 1-hexyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide (HMIM NTf2), an ionic liquid (IL). The resulting adsorbed layers were interrogated using X-ray photoelectron spectroscopy (XPS - both conventional and synchrotron-based) and spectroscopic ellipsometry.