Obstacle-enhanced spontaneous oscillation of confined active granules.

Spontaneous oscillation in particle numbers has been reported recently, in which two chambers connected by a narrow channel are alternately filled and emptied by self-propelled particles. The challenge in realizing the application of this oscillation lies in promotion of the oscillatory periodicity. By placing an asymmetric obstacle at an appropriate position near a channel opening, we can significantly improve the oscillation quality, which approaches the quality of an ideal oscillation.

Robo-Matter towards reconfigurable multifunctional smart materials.

Maximizing materials utilization efficiency via enhancing their reconfigurability and multifunctionality offers a promising avenue in addressing the global challenges in sustainability. To this end, significant efforts have been made in developing reconfigurable multifunctional smart materials, which can exhibit remarkable behaviors such as morphing and self-healing. However, the difficulty in efficiently manipulating and controlling matter at the building block level with manageable cost and complexity, which is crucial to achieving superior responsiveness to environmental clues and stimuli, has significantly hindered the further development of such smart materials.

Facile Preparation of Irradiated Poly(vinyl alcohol)/Cellulose Nanofiber Hydrogels with Ultrahigh Mechanical Properties for Artificial Joint Cartilage.

In this study, Poly(vinyl alcohol)/cellulose nanofiber (PVA/CNF) hydrogels have been successfully prepared using γ-ray irradiation, annealing, and rehydration processes. In addition, the effects of CNF content and annealing methods on the hydrogel properties, including gel fraction, micromorphology, crystallinity, swelling behavior, and tensile and friction properties, are investigated. Consequently, the results show that at an absorbed dose of 30 kGy, the increase in CNF content increases the gel fraction, tensile strength, and elongation at break of irradiated PVA/CNF hydrogels, but decreases the water absorption.

Alginate-based hydrogels mediated biomedical applications: A review.

With the development in the field of biomaterials, research on alternative biocompatible materials has been initiated, and alginate in polysaccharides has become one of the research hotspots due to its advantages of biocompatibility, biodegradability and low cost. In recent years, with the further understanding of microscopic molecular structure and properties of alginate, various physicochemical methods of cross-linking strategies, as well as organic and inorganic materials, have led to the development of different properties of alginate hydrogels for greatly expanded applications. In view of the potential application prospects of alginate-based hydrogels, this paper reviews the properties and preparation of alginate-based hydrogels and their major achievements in delivery carrier, dressings, tissue engineering and other applications are also summarized.

Biomimetic Synchronization in Biciliated Robots.

Direct mechanical coupling is known to be critical for establishing synchronization among cilia. However, the actual role of the connections is still elusive-partly because controlled experiments in living samples are challenging. Here, we employ an artificial ciliary system to address this issue.

Odd Response-Induced Phase Separation of Active Spinners.

Due to the breaking of time-reversal and parity symmetries and the presence of non-conservative microscopic interactions, active spinner fluids and solids respectively exhibit nondissipative odd viscosity and nonstorage odd elasticity, engendering phenomena unattainable in traditional passive or active systems. Here, we study the effects of odd viscosity and elasticity on phase behaviors of active spinner systems. We find the spinner fluid under a simple shear experiences an anisotropic gas-liquid phase separation driven by the odd-viscosity stress.

Morphology-Tailored Dynamic State Transition in Active-Passive Colloidal Assemblies.

Mixtures of active self-propelled and passive colloidal particles promise rich assembly and dynamic states that are beyond reach via equilibrium routes. Yet, controllable transition between different dynamic states remains rare. Here, we reveal a plethora of dynamic behaviors emerging in assemblies of chemically propelled snowman-like active colloids and passive spherical particles as the particle shape, size, and composition are tuned.

Regulation of Photogenerated Redox Species through High Crystallinity Carbon Nitride for Improved C-S Coupling Reactions.

A novel and efficient approach for the synthesis of α, β-unsaturated sulfones through heterogeneous photocatalyzed C-S coupling reactions have been developed. The use of molten-salt method derived carbon nitride (MCN), a transition metal-free polymeric photocatalyst, combined with enhanced crystallinity and potassium iodide as an additive, effectively modulates photogenerated reactive redox species, markedly increasing the overall reaction selectivity. This method achieves the shortest reaction time (2 h) with high yield (up to 95 %) among the reported heterogeneous catalytic C-S bond formation reactions, matching the efficiency of the homogeneous photocatalysts.

Active self-assembly of colloidal machines with passive rotational parts coordination of phoresis and osmosis.

The organization of microscopic objects into specific structures with movable parts is a prerequisite for building sophisticated micromachines with complex functions, as exemplified by their macroscopic counterparts. Here we report the self-assembly of active and passive colloids into micromachinery with passive rotational parts. Depending on the attachment of the active colloid to a substrate, which varies the degrees of free freedom of the assembly, colloidal machines with rich internal rotational dynamics are realized.

Hydrodynamics-Induced Long-Range Attraction between Plates in Bacterial Suspensions.

We perform optical-tweezers experiments and mesoscale fluid simulations to study the effective interactions between two parallel plates immersed in bacterial suspensions. The plates are found to experience a long-range attraction, which increases linearly with bacterial density and decreases with plate separation. The higher bacterial density and orientation order between plates observed in the experiments imply that the long-range effective attraction mainly arises from the bacterial flow field, instead of the direct bacterium-plate collisions, which is confirmed by the simulations.

Orientational Order in Dense Colloidal Liquids and Glasses.

We construct structural order parameters based on local angular and radial distribution functions in dense colloidal suspensions. All the order parameters show significant correlations to local dynamics in the supercooled and glass regime. In particular, the correlations between the orientational order and dynamical heterogeneity are consistently higher than those between the conventional two-body structural entropy and local dynamics.

Constraint dependence of pressure on a passive probe in an active bath.

Mechanical pressure in active matter is generally not a state variable and possesses abnormal properties, in stark contrast to equilibrium systems. We here show that the pressure on a passive probe exerted by an active fluid even depends on external constraints on the probe by means of simulation and theory, implying that the mechanical pressure is not an intrinsic physical quantity of active systems. The active mechanical pressure on the passive probe significantly increases and saturates as its elastic constraint (realized by a trap potential) or kinematic constraint (realized by environmental friction) strengthens.

High-Resolution Volumetric Imaging and Classification of Organisms with Standard Optical Microscopy.

Three-dimensional (3D) characterization of organisms is important for the study of cellular phenotypes, structural organization, and mechanotransduction. Existing optical techniques for 3D imaging rely on focus stacking or complex multiangle projection. Focus stacking has deleterious axial resolution due to the one-angle optical projection.

Evidence for growing structural correlation length in colloidal supercooled liquids.

Using video microscopy, we measure the long-time diffusion coefficients of colloidal particles at different concentrations. The measured diffusion coefficients start to deviate from theoretical predictions based on random collision models upon entering the supercooled regime. The theoretical diffusion relation is recovered by assigning an effective mass proportional to the size of structurally correlated clusters to the diffusing particles, providing an indirect method to probe the growth of static correlation length scales approaching the glass transition.

Odd viscosity-induced Hall-like transport of an active chiral fluid.

Broken time-reversal and parity symmetries in active spinner fluids imply a nondissipative "odd viscosity," engendering phenomena unattainable in traditional passive or active fluids. Here we show that the odd viscosity itself can lead to a Hall-like transport when the active chiral fluid flows through a quenched matrix of obstacles, reminiscent of the anomalous Hall effect. The Hall-like velocity depends significantly on the spinner activity and longitudinal flow due to the interplay between odd viscosity and spinner-obstacle collisions.

Learned irrelevant stimulus-response associations and proportion congruency effect: A diffusion model account.

The increased Simon effect with increasing the ratio of congruent trials may be interpreted by both attention modulation and irrelevant stimulus-response (S-R) associations learning accounts, although the reversed Simon effect with increasing the ratio of incongruent trials provides evidence supporting the latter account. To investigate if learning irrelevant S-R associations is a common mechanism underlying the proportion congruency (PC) effect of the Simon task, we employed a variant of diffusion model, diffusion model for conflict tasks (DMC), to test which theory can simultaneously account for the mean reaction time (RT) and RT distribution patterns of the Simon effect in different PC conditions. Simulation results showed that the DMC modulating starting point according to learned irrelevant S-R associations rather than drift criterion or attention-related parameters (i.

A Chemotactic Colloidal Motor.

Chemotaxis plays a crucial role in the realization of various functions of human life such as fertilization, immune function, inflammatory response, regeneration processes, etc. Inspired by the natural chemotaxis, colloidal motors with chemotactic ability can realize intelligent sense and targeted navigation, which bring a revolutionary method to biomedical applications like precision medicine. However, the application in the biomedical field requires the colloidal motors with submicrometer scale, strong chemotactic ability and clear chemotactic mechanism.

Photocatalytic cyclization of nitrogen-centered radicals with carbon nitride through promoting substrate/catalyst interaction.

The use of metal-free carbon nitride and light to drive catalytic transformations constitutes a sustainable strategy for organic synthesis. At the moment, enhancing the intrinsic activity of CN catalysts by tuning the interfacial coupling between catalyst and substrate remains challenging. Herein, we demonstrate that urea-derived carbon nitride catalysts with the abundant -NH groups and the relative positive charged surface could effectively complex with the deprotonated anionic intermediate to improve the adsorption of organic reactants on the catalyst surface.

Light-driven single-cell rotational adhesion frequency assay.

Unlabelled: The interaction between cell surface receptors and extracellular ligands is highly related to many physiological processes in living systems. Many techniques have been developed to measure the ligand-receptor binding kinetics at the single-cell level. However, few techniques can measure the physiologically relevant shear binding affinity over a single cell in the clinical environment.

Lattice Induced Short-Range Attraction between Like-Charged Colloidal Particles.

We perform experiments and computer simulations to study the effective interactions between like-charged colloidal tracers moving in a two-dimensional fluctuating background of colloidal crystal. By a counting method that properly accounts for the configurational degeneracy of tracer pairs, we extract the relative probability of finding a tracer pair in neighboring triangular cells formed by background particles. We find that this probability at the nearest neighbor cell is remarkably greater than those at cells with larger separations, implying an effective attraction between the tracers.

Transparent, photothermal and stretchable alginate-based hydrogels for remote actuation and human motion sensing.

Multifunctional hydrogels show potential applications in actuators and wearable sensors. However, it is still a challenge to develop a photothermal responsive conductive hydrogel with high transparency, mechanical properties, broad sensing range, and low-temperature resistance. In this work, a transparent, photothermal responsive, and highly stretchable alginate-based hydrogels was feasibly constructed by adding two-dimensional non-layered molybdenum dioxide nanosheets (2D-MoO) to sodium alginate/polyacrylamide mixture and then soaking into the calcium chloride solution.