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Self-assembly of colloidal particles enables the versatile fabrication of highly ordered structures and materials for optical, sensing, and other applications. Nevertheless, many traditional assembly processes are inefficient, because there exists an inevitable contradiction between time efficiency and crystalline quality. In this work, we introduce an ultrafast, robust, and scalable approach of imbibition-induced assembly. We assume that the instantaneous solvent imbibition induced by the nanoporous media could direct ultrafast self-assembly of colloidal particles into ordered structures.Self-assembly of colloidal particles from a droplet on a nanoporous substrate was firstly observed and investigated. A phase diagram of the thickness of the colloidal crystal as a function of the printing speed and the particle volume fraction was presented through systematic experiments.The nanoporous substrate can induce strong capillary flow that will directthe rapid self-assemblyof particles intocolloidalcrystals. The imbibition-induced assembly was spatially and temporally combined with the meniscus-guided printing approach, and the printing speed can be improved by two orders of magnitude than the traditional evaporative assembly methods. We finally demonstrate an effective and ultrafast approach for assembling colloidal particles into photonic crystals with controllable sizes and shapes on the macroscale.

The strength of polycrystal increases as the grain diameter l decreases, i.e. the Hall–Petch behaviour. This trend reverses at about 3 l l l to merely a few particles, resulting in ultrafine-grained solids termed as glass-crystal composites. Beyond the conventional Hall–Petch strengthening and inverse-Hall–Petch softening, we observe a power-law strengthening at l l = 14 particles featured with peaks of various quantities, which deepens the understanding on softening–strengthening transition.

Edible bird’s nest (EBN) is a Chinese delicacy possessing skin rejuvenating functions. To verify skin anti-inflammatory function of EBN, water extract and enzymatic digest of EBN, as well as the major sialic acid, N-acetyl neuraminic acid (NANA), were probed in TNF-α-treated HaCaT keratinocytes. The mRNA expressions of pro-inflammatory cytokines, e.g., IL-1β, IL-6, TNF-α, and an enzyme responsible for inflammatory response, i.e., Cox-2, as well as filaggrin and filaggrin-2, were markedly altered after treating with different preparations of EBN. The EBN-mediated responses could be accounted by its robust reduction of reactive oxygen species (ROS), NF-κB signaling and phosphorylation of p38 MAPK and JNK, as triggered by TNF-α-induced inflammation. The anti-inflammatory response of EBN was further supported in animal model. In 2,4-dinitrochlorobenzene (DNCB)-induced dermatitic mice, the effects on skin thickness, severity level of damage and scratching behavior, exerted by DNCB, were reversed after EBN treatments, in dose-dependent manners. In parallel, the levels of immune cells and pro-inflammatory cytokines in dermatitic skin were markedly reduced by treatment of EBN preparations. In general, NANA and enzymatic digest of EBN showed better anti-inflammatory responses in both models of in vitro and in vivo. These lines of evidence therefore suggest the possible application of EBN in treating atopic dermatitis.

The hydrodynamic interactions (HIs) of two colloidal spheres characterized by the translation–translation (T–T) couplings have been studied under various confinements, but little is known regarding the HIs of anisotropic particles and rotational motions, which are common in nature and industry. Here, we study the T–T, rotation–rotation (R–R) and translation–rotation (T–R) hydrodynamic couplings of two colloidal ellipsoids sediment on the bottoms of channels in experiment, theory and simulation. We find that the degree of confinement and the particle shape anisotropy are critical tuning factors resulting in anomalous hydrodynamic and diffusive behaviours. The negative R–R coupling reflects the tendency of opposite rotations of two neighbouring ellipsoids. The positive T–R coupling reflects that an ellipsoid rotates away from the channel axis as another ellipsoid approaches. As the channel width increases, the positive T–T coupling changes to an abnormal negative coupling, indicating that the single-file diffusion can exist even in wide channels. By contrast, only positive T–T couplings were observed for spheres in channels. The T–T coupling increases with the aspect ratio p. The R–R coupling is the maximum at a moderate p ~ 2.8. The T–R coupling is the maximum at a moderate degree of confinement. The spatial range of HIs is longer than that of spheres and increases with p. We propose a simple model which reproduces some coupling phenomena between two ellipsoids, and it is further confirmed by low-Reynolds-number hydrodynamic simulation. These findings shed new light on anisotropic particle diffusion in porous media, transport through membranes, microfluidics and microrheology.

Acetylcholinesterase (AChE) hydrolyses acetylcholine to choline and acetate, playing an important role in terminating the neurotransmission in brain and muscle. Recently, the non-neuronal functions of AChE have been proposed in different tissues, in which there are various factors to regulate the expression of AChE. In mammalian skin, AChE was identified in melanocytes and keratinocytes. Our previous study has indicated that AChE in keratinocyte affects the process of solar light-induced skin pigmentation; however, the expression of AChE in keratinocytes in responding to sunlight remains unknown. Here, we provided several lines of evidence to support a notion that AChE could be upregulated at transcriptional and translational levels in keratinocytes when exposed to solar light. The light-mediated AChE expression was triggered by Ca2+, supported by an induction of Ca2+ ionophore A23187 and a blockage by Ca2+ chelator BAPTA-AM. In addition, this increase on AChE transcriptional expression was eliminated by mutagenesis on the activating protein 1 (AP1) site in ACHE gene. Hence, the solar light-induced AChE expression is mediated by Ca2+ signalling through AP1 site. This finding supports the role of solar light in affecting the cholinergic system in skin cells, and which may further influence the dermatological function.

Two critical behaviors in glasses of ellipsoids show thermodynamic and dynamic glass transitions with distinct relaxation., Critical-like behaviors have been found in translational degrees of freedom near the glass transition of spherical particle systems mainly with local polycrystalline structures, but it is not clear if criticality exists in more general glassy systems composed of nonspherical particles without crystalline structures. Here, through experiments and simulations, we show critical-like behaviors in both translational and rotational degrees of freedom in monolayers of monodisperse colloidal ellipsoids in the absence of crystalline orders. We find rich features of the Ising-like criticality in structure and slow dynamics at the ideal glass transition point ϕ0, showing the thermodynamic nature of glass transition at ϕ0. A dynamic criticality is found at the mode-coupling critical point ϕc for the fast-moving clusters whose critical exponents increase linearly with fragility, reflecting a dynamic glass transition. These results cast light on the glass transition and explain the mystery that the dynamic correlation lengths diverge at two different temperatures.

The thermal stability and decomposition kinetics analysis of 1-alkyl-2,3-dimethylimidazole nitrate ionic liquids with different alkyl chains (ethyl, butyl, hexyl, octyl and decyl) were investigated by using isothermal and nonisothermal thermogravimetric analysis combined with thermoanalytical kinetics calculations (Kissinger, Friedman and Flynn-Wall-Ozawa) and density functional theory (DFT) calculations. Isothermal experiments were performed in a nitrogen atmosphere at 240, 250, 260 and 270 °C. In addition, the nonisothermal experiments were carried out in nitrogen and air atmospheres from 30 to 600 °C with heating rates of 5, 10, 15, 20 and 25 °C/min. The results of two heating modes, three activation energy calculations and density functional theory calculations consistently showed that the thermal stability of 1-alkyl-2,3-dimethylimidazolium nitrate ionic liquids decreases with the increasing length of the alkyl chain of the substituent on the cation, and then the thermal hazard increases. This study could provide some guidance for the safety design and use of imidazolium nitrate ionic liquids for engineering.

A defect-free crystal can be superheated into a metastable state above its melting point and eventually melts via homogeneous nucleation. Further increasing the temperature leads to the metastable crystal becoming unstable and melting catastrophically once beyond its superheat limit. The homogeneous melting is not well studied near the superheat limit and this limit is difficult to measure accurately, even for the simplest model of hard-sphere crystals. Here our molecular-dynamics simulations identify its superheat limit at volume fraction φlimit = 0.494 ± 0.003, which is higher than the previous theoretical estimations. We found that the hard-sphere crystal at the superheat limit does not satisfy Born's melting criterion, but has a vanishing bulk modulus, i.e. a spinodal instability, which preempts other thermodynamic or mechanical instabilities. At the strong superheating regime, the nucleation deviates from the assumptions in the classical nucleation theory. In contrast to crystallization which often develops nuclei with various intermediate structures, the melting of face-centered cubic (fcc) hard-sphere crystal does not produce intermediate structures such as body-centered cubic (bcc) crystallites although bcc is more stable than fcc at the strong superheating regime. Moreover, we found that the time evolutions of the order parameters and the pressure all exhibit a compressed exponential function, in contrast to the stretched exponential relaxation of supercooled liquids. The compressed exponential functions have the same exponent, which poses a new challenge to theory.

Background Melanoma is a lethal cancer. NF-κB has been validated as a molecular target for melanoma treatment. Current therapies for melanoma have limitations. Novel targeted therapeutics are needed. Arnicolide D (Ar-D), a sesquiterpene lactone isolated from the dried whole plant of Centipeda minima (L.) A. Br. et Aschers., has been reported to inhibit NF-κB activity in colorectal cancer cells. Purpose To investigate the anti-melanoma effects of Ar-D in vitro and in vivo; and to determine whether Ar-D inhibits the NF-κB pathway in melanoma cells. Methods A B16F10 allograft mouse model and two melanoma cell lines (A375 and B16F10) were used to investigate the anti-melanoma effects of Ar-D in vivo and in vitro. Dacarbazine was used as a positive control. Cell viability was assessed by MTT and crystal violet staining assays. Cell cycle arrest and apoptosis were analyzed by flow cytometry. Protein levels were determined by Immunoblotting. Results In vivo assays showed that the average tumor weight in Ar-D-treated group (4 mg/kg, i.p, 15 days) was reduced by 53.7%, when compared with the control group. In vitro studies demonstrated that Ar-D reduced cell viability, induced G2/M cell cycle arrest and apoptosis, elevated levels of cell cycle regulatory proteins p53 and p21, and lowered levels of G2/M checkpoint proteins Cdc2 and Cyclin B1 in melanoma cells. Mechanistically, Ar-D inhibited the activity of IKKα/β, the degradation of IκBα, and the phosphorylation and expression of NF-κB p65 in melanoma cells. Conclusion Ar-D has anti-melanoma effects, and inhibition of the IKK/IκBα/NF-κB p65 pathway is involved in the effects.

Homogeneous Melting The nucleation and melting of crystals are primarily driven by surfaces and defects, which can lower the thermodynamic barrier to a phase transition. A harder problem to study is when the transition occurs uniformly. Wang et al. (p. 87 ; see the Perspective by Weeks ) imaged the homogeneous melting of superheated colloidal crystals using a laser to initiate the melting at the interior of the crystal. The authors were then able to track nucleation precursors and nucleus evolution and to find where defects and instabilities limited the homogeneous melting process.

Glass formers constitute of anisotropic particles was mainly studied by simulations in three dimensions with incomplete phase diagrams. Here we studied the structures and the glassy dynamics for translational and rotational motions in quasi-two dimensional (2D) suspensions of colloidal ellipsoids at the single-particle level. At high densities, ellipsoids with large aspect ratio formed psuedo-nematic domains. Video microscopy revealed a two-step glass transition: rotational motion first becomes glassy due to the inter-domain freezing, then translational motion become glassy at a higher density due to inner-domain freezing. Between the two transitions, ellipsoids formed an "orientational glass". Below and near the respective glass transition densities, the rotational and translational fastest-moving particles moved cooperatively and formed clusters with power-law size distributions. The mean cluster sizes diverge in power law as approaching the glass transitions. The fast translational particles concentrated in pseudonematic domains and form band-like clusters while the fast rotational particles mainly located around domain boundaries and form branch-like clusters.

We directly observed the kinetics of homogeneous melting in 3D superheated colloidal crystals at single-particle resolution by video microscopy. We found that the precursor of nuclei is in fact local particle exchanges surrounded by particles with large displacement amplitudes rather than any types of defects. The critical size, incubation time, shape evolution of nucleus were measured under different degrees of superheating.

We observed a two-step glass transition in monolayers of colloidal ellipsoids by video microscopy. The glass transition in the rotational degree of freedom was at a lower density than that in the translational degree of freedom. Between the two transitions, ellipsoids formed an orientational glass. Approaching the respective glass transitions, the rotational and translational fastest-moving particles in the supercooled liquid moved cooperatively and formed clusters with power-law size distributions. The mean cluster sizes diverge in power law as approaching the glass transitions. The clusters of translational and rotational fastest-moving ellipsoids formed mainly within pseudo-nematic domains, and around the domain boundaries, respectively.

In this paper, cooperative self-assembly (CSA) of colloidal spheres with different sizes was studied. It was found that a complicated jamming effect makes it difficult to achieve an optimal self-assembling condition for construction of a well-ordered stacking of colloidal spheres in a relatively short growth time by CSA. Through the use of a characteristic infrared (IR) technique to significantly accelerate local evaporation on the growing interface without changing the bulk growing environment, a concise three-parameter (temperature, pressure, and IR intensity) CSA method to effectively overcome the jamming effect has been developed. Mono- and multiscale inverse opals in a large range of lattice scales can be prepared within a growth time (15-30 min) that is remarkably shorter than the growth times of several hours for previous methods. Scanning electron microscopy images and transmittance spectra demonstrated the superior crystalline and optical qualities of the resulting materials. More importantly, the new method enables optimal conditions for CSA without limitations on sizes and materials of multiple colloids. This strategy not only makes a meaningful advance in the applicability and universality of colloidal crystals and ordered porous materials but also can be an inspiration to the self-assembly systems widely used in many other fields, such as nanotechnology and molecular bioengineering.

To better understand the laser drilling process and especially to clarify keyhole dynamics in metal drilling, a quasi-two-dimensional drilling assembly was set up with a thin sandwich structure. Keyhole dynamics coupling multiple physical processes were recorded using high-speed photography, and clear images were obtained. The formation of keyholes was found not to be a single unified process, and the whole drilling process could be divided into five stages: an initial melt ejection, mild melting, rapid drilling, hole expansion, and backflow and recasting. As the keyhole evolved, the removal of material changed.

We studied the self-diffusion of colloidal ellipsoids in a monolayer near a flat wall by video microscopy. The image processing algorithm can track the positions and orientations of ellipsoids with sub-pixel resolution. The translational and rotational diffusions were measured in both the lab frame and the body frame along the long and short axes. The long-time and short-time diffusion coefficients of translational and rotational motions were measured as functions of the particle concentration. We observed sub-diffusive behavior in the intermediate time regime due to the caging of neighboring particles. Both the beginning and the ending times of the intermediate regime exhibit power-law dependence on concentration. The long-time and short-time diffusion anisotropies change non-monotonically with concentration and reach minima in the semi-dilute regime because the motions along long axes are caged at lower concentrations than the motions along short axes. The effective diffusion coefficients change with time t as a linear function of (lnt)/t for the translational and rotational diffusions at various particle densities. This indicates that their relaxation functions decay according to 1/t which provides new challenges in theory. The effects of coupling between rotational and translational Brownian motions were demonstrated and the two time scales corresponding to anisotropic particle shape and anisotropic neighboring environment were measured.

A concise pressure controlled isothermal heating vertical deposition (PCIHVD) method is developed, which provides an optimal growing condition with better stability and reproducibility for fabricating photonic crystals (PCs) without the limitation of colloidal sphere materials and sizes. High quality PCs are fabricated with PCIHVD from polystyrene spheres with diameters ranging from 200 nm to 1 mu m. The deep photonic band gap and steep photonic band edge of the samples are most favorable for realizing ultrafast optical devices, photonic chips, and communications. This method makes a meaningful advance in the quality and diversity of PCs and greatly promotes their wide applications.