Water-in-water (W/W) emulsions are unique colloidal systems composed of two immiscible aqueous phases, featuring ultra-low interfacial tension, mild preparation conditions, and excellent biocompatibility. Owing to their distinctive interfacial properties and non-toxic aqueous environment, W/W emulsions have attracted extensive attention across colloid and interface science, food science, biomedicine, and pharmaceutical engineering, and have gradually become a hot research topic in interdisciplinary fields. In particular, recent advances have highlighted the importance of nanoparticle-stabilized Pickering W/W emulsions, which provide enhanced stability despite the intrinsically ultralow interfacial tension of such systems. This paper reviews the formation and phase separation mechanisms of W/W emulsions, summarizes the characteristics and stabilization strategies of Pickering stabilizers, discusses the regulatory rules of colloidal particle intrinsic properties, interfacial characteristics, and external environmental factors on emulsion stability, and explores their applications in the environment, medicine, food, and other fields. Finally, current challenges and future perspectives for the development of stable and functional W/W Pickering emulsions are discussed.

Robust hydrogel composites were fabricated through a one-step chemical gelation route using carboxymethyl cellulose, acrylamide, and a fixed gold nanoparticle-containing formulation platform to obtain impact-resistant materials with composition-dependent swelling and mechanical responses. Increasing cellulose content progressively reinforced the network, raising tensile strength from 3.68 to 10.79 MPa, increasing compressive strength by 3.3 MPa, and enabling complete resilience recovery of 100%, while dynamic mechanical analysis showed concurrent increases in storage modulus and loss modulus, consistent with improved energy storage and dissipation. Wettability and swelling were likewise governed by network density, with cellulose-rich formulations showing lower equilibrium water uptake and higher water contact angles, whereas swelling remained stimulus-responsive, decreasing at 65 °C relative to 25 °C and increasing markedly at pH 13. Swelling kinetics were well described by Higuchi and Korsmeyer-Peppas behavior, indicating coupled diffusion and network relaxation during water uptake. To predict swelling ratio, a machine learning workflow was implemented using grouped cross-validation that held out complete formulation, pH, and temperature condition groups, with formulation percentage, pH, temperature, and time as inputs. Under this conservative protocol, the random forest model delivered the best mean fold performance, with a mean R2 of 0.652 ± 0.257, while the aggregated held-out prediction series reached an R2 of 0.842. The CEL4 composite also protected glass from shattering in bottle, ball, and hammer impact demonstrations, highlighting strong cushioning behavior. These results establish cellulose-tuned p(CEL/AAm)/Au hydrogel composites as promising protective layers with predictable swelling behavior, while Au nanoparticle-specific contributions remain to be isolated by future control studies.

A novel strategy for eradicating biofilms by enhancing antibiotic penetration is presented through the development of a photo-responsive, micropump-engineered surface. This surface features black titanium oxide (B-TiO2) colloidal particles immobilized on a titanium substrate, a material commonly used in biomedical implants. When exposed to near-infrared (NIR) light, the engineered surface induces localized thermal convection flows within the biofilm and simultaneously generates reactive oxygen species (ROS). These physical and chemical effects act synergistically to disrupt the biofilm architecture. Remarkably, only 20 min of NIR irradiation leads to a significant reduction in the biomass of Staphylococcus aureus biofilms on the micropump surface. This effect is mediated by two complementary mechanisms: thermal convection-driven water flow and ROS-induced degradation of the extracellular polymeric substance (EPS), which forms the structural scaffold of the biofilm. As a result, the antibacterial activity of gentamicin is enhanced by approximately five-fold in vitro and ten-fold in vivo in a rat subcutaneous infection model. Furthermore, the B-TiO2 micropump exhibits excellent biocompatibility, showing no adverse effects in either in vitro or in vivo assessments. This innovative photo-responsive approach provides a promising solution for addressing biofilm-related infections on medical device surfaces by effectively disrupting biofilms and markedly improving antibiotic efficacy.

Bacteria-derived carbon-quantum-dots (CQDs) have been proposed for different applications, amongst which biofilm control. Anti-biofilm activities of bacteria-derived CQDs result from generation of reactive-oxygenspecies (ROS), but the key-chemical pathways of carbonization of bacterial components and ROS-generation by bacteria-derived CQDs are unknown. Formation of low-yield, bacteria-derived CQDs (diameter 2-3 nm) upon hydrothermal-carbonization was confirmed using UV-vis absorption and fluorescence-emission spectroscopy. Amide-bands characteristic in FTIR spectra of source-bacteria remained visible in bacteria-derived CQDs. XPS indicated an N1s photo-electron binding energy peak at 399.5 eV in source-bacteria due to amines that were converted upon carbonization into pyrrolic (400.5 eV) and graphitic (401.8 eV) nitrogen in bacteria-derived CQDs. A C1s peak at 288.4 eV in source-bacteria due to carboxyl-groups related with the occurrence of amines in bacteria, but disappeared upon carbonization. Relations between the occurrence of amine nitrogen in source-bacteria with pyrrolic and graphitic nitrogen in bacteria-derived CQDs confirm that bacterial proteins are converted into pyrrolic and graphitic nitrogen-species upon hydrothermal carbonization. Relations between ROS-generation with the occurrence of pyrrolic and graphitic nitrogen-species identified these nitrogen-species in bacteria-derived CQDs as being responsible for enhanced ROS-generation and accompanying anti-biofilm activity. These findings enable selection of source-bacteria for preparing bacteria-derived CQDs with optimized ROS-generation and anti-biofilm activity.

The limitations of conventional hydrogels have spurred a growing interest in enhancing polymeric compounds with inorganic nanoparticles to create hydrogel composites with multifunctional properties for various applications. This study reports a one-step chemical gelation system for fabricating hydrogel composites consisting of carboxymethyl cellulose, acrylamide, and gold nanoparticles. The hydrogel composites exhibited significant mechanical and adhesive strength attributed to the strong hydrogen-bonding interaction within the polymer network. Remarkably, the composites achieved a tensile strength of 22.8 MPa with a yield strain of 877.1%, a compressive strength of 346.8 MPa with a yield strain of 120%, and an adhesion strength of 246 kPa. The materials also demonstrated remarkable adhesion performance on different biological and inorganic substrates, maintaining higher adhesion stress across a range of displacements. Furthermore, the hydrogel composites exhibited superior bactericidal activity, achieving up to 98.2% efficacy against E. coli and 99.1% against S. aureus, while showing non-toxicity to mammalian cells. These findings highlight the practical potential of these hydrogel composites in applications such as wound healing and antibacterial bioadhesives.

Using video microscopy, we experimentally investigate how a periodic potential landscape influences the dynamics of colloidal monolayers. The potential is generated by a layer of densely packed particles immobilized on the substrate, creating a spatially periodic gravitational field. In the absence of this external landscape, the monolayer behaves as a supercooled liquid: particles are temporarily confined by cages formed by neighboring particles but can escape over long time scales, allowing diffusive motion and structural rearrangement. As the strength of the imposed potential increases, the system undergoes a dynamical arrest. Particles become increasingly trapped in local minima of the external potential, leading to a dramatic slowdown of particle dynamics and a suppression of structural rearrangements. This strong spatial localization also hinders the cooperative motion of particles. As a result, dynamical heterogeneity is significantly reduced during the dynamical arrest. Our results show the critical role of the energy landscape in tuning colloidal dynamics and offer insight into dynamical arrest processes in complex environments.

Coagulation within blood vessels is a major cause of cardiovascular disease and global mortality, highlighting the urgent need for effective anticoagulant strategies. In this study, we introduce a dynamic and highly efficient anticoagulant platform, achieved through the fabrication of a novel colloidal microrobot with unique functional properties. The microrobot is a Janus colloidal sphere with one hemisphere coated with heparin-mimicking polymers and the other with gold. This structure endows the microrobot with self-propulsion capabilities, powered by biocompatible near-infrared (NIR) irradiation, without the need for chemical fuel. The heparin-mimicking polymers not only prevent blood clotting but also promote endothelial cell growth while inhibiting the proliferation of smooth muscle cells. Additionally, the self-propulsion feature allows the microrobot to travel long distances within blood vessels and precisely target sites for anticoagulation. Our work validates an approach for the production of biofunctionalized microrobots, which introduces a novel avenue for anticoagulation application through the development of innovative biofunctionalized colloidal devices.

We report the synthesis of SiO2 colloidal rings coated with TiO2, which enable photoresponsive self-assembly into porous ordered structures and hybrid assembly for the capture and release of non-active colloids in a hydrogen peroxide (H2O2) solution. Such assemblies originate from a concentration gradient generated by the TiO2-mediated decomposition of H2O2 under ultraviolet (UV) irradiation. The work provides a straightforward strategy to fabricate active colloids with ring-like shapes for the controlled assembly of open crystalline colloidal materials.

Harmful planktonic bacteria pose significant threats to human health and industrial productivity. While various methods have been developed to eliminate bacteria in solution, effective and straightforward strategies for both killing bacteria and subsequently removing them remain challenging. In this study, we propose a versatile strategy that combines killing and aggregation of planktonic bacteria using colloidal particles with charges opposite those of the bacteria. The electrostatic attraction between the colloids and bacteria enhances close contact, enabling the colloids to effectively disrupt bacterial membranes and compromise their structural integrity. Additionally, this interaction induces the generation of reactive oxygen species, which further damages bacterial DNA. Notably, the colloidal particles also function as bacteria linkers, promoting the aggregation of bacteria through electrostatic attraction and thereby facilitating their separation from the solution. However, an excessively high concentration of the colloidal particles was found to eliminate bacterial aggregates and restore a dispersed state, as the bacteria become completely coated by the particles, thus disrupting the particles' linker function. This work highlights the significant potential of charged colloidal particles in antibacterial applications and provides a simple and effective approach for killing and removing planktonic bacteria.

Aggregation-induced emission (AIE) materials have gained significant attention for their unique fluorescence enhancement in the aggregated state. However, combining rigid polymers with AIE molecules to enhance luminescent properties remains to be investigated. In this work, two novel AIE-active polyarylethersulfone (PAES) derivatives are synthesized by incorporating tetraphenylethene (TPE) into either the side chain or main chain of PAES, resulting in side-chain polyarylethersulfone-tetraphenylethene (PAES-TPE) and main-chain polyarylethersulfone-tetraphenylethene (m-PAES-TPE), respectively. These derivatives are designed to investigate the influence of the rigid polymer backbone on the AIE properties of TPE. The incorporation of TPE into PAES resulted in a notable redshift in fluorescence emission compared to pure TPE. Notably, m-PAES-TPE50%, a polymer with 50% molar content of TPE, exhibited a fluorescence quantum yield to 57.43%, more than twice that of TPE powder. Thermal analysis showed that both PAES-TPE and m-PAES-TPE have excellent thermal stability and temperature-dependent fluorescence. Additionally, these materials are processed into hydrophobic nanoparticles, and in vitro experiments demonstrated good fluorescence properties and biocompatibility for cancer cell bioimaging. This work highlights the potential of rigid AIE-active PAES derivatives for advanced bioimaging applications.

The integration of machine learning (ML) in materials fabrication has seen significant advancements in recent scientific innovations, particularly in the realm of 3D/4D printing. ML algorithms are crucial in optimizing the selection, design, functionalization, and high-throughput manufacturing of materials. Meanwhile, 3D/4D printing with responsive material components has increased the vast design flexibility for printed hydrogel composite materials with stimuli responsiveness. This review focuses on the significant developments in using ML in 3D/4D printing to create hydrogel composites that respond to stimuli. It discusses the molecular designs, theoretical calculations, and simulations underpinning these materials and explores the prospects of such technologies and materials. This innovative technological advancement will offer new design and fabrication opportunities in biosensors, mechatronics, flexible electronics, wearable devices, and intelligent biomedical devices. It also provides advantages such as rapid prototyping, cost-effectiveness, and minimal material wastage.

We investigate the Brownian motion of isolated snowman-shaped particles consisting of pairs of large and small spheres by video microscopy. Our observations reveal that the particle exhibits varying degrees of anisotropic translational diffusion depending on the reference point used for tracking. In particular, when tracking the snowman's geometrical center, the diffusion coefficient along the particle's long axis (Da) is greater than that along the short axis (Db). When tracking the large sphere's center, Da and Db are identical, while tracking the small sphere's center results in Da being smaller than Db. Since Da remains constant across these geometrical centers, the higher Db thus leads to the fastest diffusion for the small sphere's center. These differences in diffusion arise from the varying coupling between translational and rotational motions, determined by the tracking points relative to the center of hydrodynamic stress (CoH). The CoH has been experimentally confirmed to be the geometrical center of the snowman-shaped particle. Our findings are consistent with the Langevin theory for the Brownian motion of anisotropic particles.

Traditional antimicrobial strategies usually indiscriminately target both harmful and beneficial microorganisms, leading to the development of microbial resistance and reducing bactericidal efficacy. Therefore, the pressing challenge lies in the precise and efficient targeting and elimination of pathogenic microorganisms, while minimizing the development of drug resistance, and ensuring the prompt transportation of neutralized microorganisms to prevent further growth and proliferation. In this study, we propose an innovative antimicrobial approach by designing and preparing magnetic, bowl-shaped colloids for bacterial capture and transport. The colloids were found to capture S. aureus of a complementary shape and size when depletion agents were presented. In addition, due to the magnetic components, these colloids enable directional movement and transport of bacteria under a magnetic field, thereby achieving decontamination and antibacterial functions. This study underscores the potential of these bowl-shaped colloids for targeted capture, controlled transportation, and efficient elimination of bacteria, highlighting the unique promise of anisotropic colloids in developing new antimicrobial strategies.

Directional light source not only helps to advance scientific progresses but also has great potentials in many application fields. However, it is still challenging to achieve the directional white light without optical elements. Here, we report a highly directional white-light emitter driven by 1064 nm near-infrared laser with 1/60 solid angle that does not require the introduction of optical elements. The emitter which consists of binary components, i.e. carbon dot and titanium oxide, possesses a microlens-shape surface formed during the synthesis process. Upon near-infrared light excitation, carbon dot emits white light based on a fundamentally different mechanism, which may involve a process similar to bremsstrahlung, multiphoton and thermal processes. The emitted white light is then regulated in the near field by the microlens-shape surface due to the confinement effect, resulting in the high directionality. The highly directional white-light emitter exhibits excellent stability and repeatability, making it promising for applications including targeted illumination and projection.

Light and magnetic responsive hydrogels, which demonstrate distinct responses by incorporating magnetic particles into photochromic hydrogels, have attracted considerable interest for their potential applications in smart optical devices. This study employs WO3 nanocomposites, derived from magneto-centric deep eutectic solvents (DES), to modulate the magnetic and photochromic behavior of hydrogel system containing hydroxyethyl methacrylate (HEMA) and acrylamide (Am), i.e. p(HEMA/Am). The well-dispersed WO3 nanocomposites in p(HEMA/Am)@WO3 hydrogel lead to a 15-fold increase in its magnetization. Furthermore, the incorporation of the DES-based WO3 nanocomposites enables a rapid photochromic response under UV-light irradiation, due to intermolecular charge transfer (ICT) between the WO3 nanocomposites and the hydrogel matrix. Computational studies based on DFT calculations elucidate the charge transfer mechanism and validate the experimental results. The molecular orbital and the energy gap calculations confirm that WO3 greatly improves electron transport in the hydrogel. The p(HEMA/Am)@WO3 hydrogel exhibits excellent light-responsive, reversible pattern formation on its surface under UV irradiation, thereby evidencing its superior repeatability in writing and erasing information. The study highlights the significant contribution of DES-based nanocomposites in synthesizing photo- chromic hydrogels, underscoring their importance in advancing optical materials. Moreover, this research lays the foundation for designing photochromic materials for rewritable displays and information storage systems.

Structure-dynamics correlation is one of the major ongoing debates in the glass transition, although a number of structural features have been found connected to the dynamic heterogeneity in different glass-forming colloidal systems. Here, using colloidal experiments combined with coarse-grained molecular dynamics simulations, we investigate the glass transition in monolayers of rough colloidal ellipsoids. Compared with smooth colloidal ellipsoids, the surface roughness of ellipsoids is found to significantly change the nature of glass transition. In particular, we find that the surface roughness induced by coating only a few small hemispheres on the ellipsoids can eliminate the existence of orientational glass and the two-step glass transition found in monolayers of smooth ellipsoids. This is due to the surface roughness-induced coupling between the translational and rotational degrees of freedom in colloidal ellipsoids, which also destroys the structure-dynamics correlation found in glass-forming suspensions of colloidal ellipsoids. Our results not only suggest a new way of using surface roughness to manipulate the glass transition in colloidal systems, but also highlight the importance of detailed particle shape on the glass transition and structure-dynamics correlation in suspensions of anisotropic colloids.

Owing to their extremely small size, carbon-quantum-dots (CQDs) can cross biological barriers, which makes them attractive for many biomedical and other applications. CQDs can retain key-chemical features and associated functionalities of the molecular sources they are derived from, provided a suitable synthesis method is used at relative mild carbonization temperatures. Here we demonstrate that CQDs hydrothermally-derived from chitosan or 2-hydroxypropyltrimethyl ammonium-chloride (HAC)-chitosan under pressurized conditions at 180 degrees C have a comparable elemental and molecular composition, as determined using X-ray photoelectron spectroscopy and Fourier-transform-infrared spectroscopy. In addition, both types of CQDs generated reactiveoxygen-species as an added functionality alien to their molecular carbon sources. As a result, CQDs exhibited stronger antibacterial properties against a Gram-positive Staphylococcus aureus and a Gram-negative Escherichia coli strain, while both molecular HAC-chitosan as well as CQDs derived from it had stronger antibacterial properties than molecular chitosan and chitosan CQDs due to the possession of quaternary ammonium groups in HAC-chitosan. Therewith, carbonization of chitosan and HAC-chitosan yields enhanced properties that can be beneficial in a high variety of different applications, including promotion of healing and bacterial infection control, preservation of food and beverages, pesticide control in agriculture and horticulture, water treatment and in many cosmetics and personal care products.

Planktonic bacterial presence in many industrial and environmental applications and personal health-care products is generally countered using antimicrobials. However, antimicrobial chemicals present an environmental threat, while emerging resistance reduces their efficacy. Suspended bacteria have no defense against mechanical attack. Therefore, we synthesized silica hexapods on an alpha-Fe 2 O 3 core that can be magneticallyrotated to inflict lethal cell-wall-damage to planktonic Gram -negative and Gram -positive bacteria. Hexapods possessed 600 nm long nano -spikes, composed of SiO 2 , as shown by FTIR and XPS. Fluorescence staining revealed cell wall damage caused by rotating hexapods. This damage was accompanied by DNA/protein release and bacterial death that increased with increasing rotational frequency up to 500 rpm. Lethal puncturing was more extensive on Gram -negative bacteria than on Gram -positive bacteria, which have a thicker peptidoglycan layer with a higher Young ' s modulus. Simulations confirmed that cell-wall-puncturing occurs at lower nanospike penetration levels in the cell walls of Gram -negative bacteria. This approach offers a new way to kill bacteria in suspension, not based on antimicrobial chemicals.

The global demand for data storage and information security has risen to frightening levels. This is due to the global population's paradigm shift toward digital technologies. Over the years, many materials have been explored with significant success and efficiency to drive a digital economy, however, research on stimuli-responsive materials (typically hydrogels) has been an interesting innovation in modern materials science and polymer chemistry. These developed materials are declared smart owing to their unique property and mode of design which incorporates stimuli-responsive moieties into the material structure. The external stimuli that alter the properties of the developed materials sensitive to them are largely grouped into the physical stimuli (e.g., magnetic field, light, temperature, mechanical stress, electrical field) and the chemical (e.g., pH, chemical reactions, ionic strength) stimuli. Thus, the review presents studies on stimuli-responsive hydrogel composite materials with an overview of their functional characteristics, reactions to various environmental stimuli, environmental implications, and potential uses in digital technologies. The scientific breakthrough in the production of stimuli-responsive hydrogel composites is an eye-opener for the development of novel material for improved data security, data authenticity, anti-counterfeiting devices, etc.

Bacteria can be dead, alive, or exhibit slowed or suspended life forms, making bacterial death difficult to establish. Here, agar-plating, microscopic-counting, SYTO9/propidium-iodide staining, MTT-conversion, and bioluminescence-imaging were used to determine bacterial death upon exposure to different conditions. Rank correlations between pairs of assay outcomes were low, indicating different assays measure different aspects of bacterial death. Principal-component analysis yielded two principal components, named “reproductive-ability” (PC1) and “metabolic-activity” (PC2). Plotting of these principal components in two-dimensional space revealed a dead region, with borders defined by the PC1 and PC2 values. Sensu stricto implies an unpractical reality that all assays determining PC1 and PC2 must be carried out in order to establish bacterial death. Considering this unpracticality, it is suggested that at least one assay determining reproductive activity (PC1) and one assay determining metabolic activity (PC2) should be used to establish bacterial death. Minimally, researchers should specifically describe which dimension of bacterial death is assessed, when addressing bacterial death.