Janus Particles Research Articles

Green Nanoengineered Fabrics: Waste-Derived Polyphenol-Zinc@ Silica Core-Shell Reactive Janus Nanoparticles for Functional Fabrics.

Fabricating Janus nanoparticle-functionalized fabrics with UV protection, strength enhancement, self-cleaning properties, and wash durability, with a biocompatible nature, is crucial in modern functional fabrics engineering. Particularly, tailoring multifunctional nanoparticles capable of exhibiting several distinct properties, utilizing low-cost raw materials, and adhering to green chemistry principles is pivotal. A fabrication strategy for developing multifunctional reactive Janus nanoparticles, utilizing waste-derived natural polyphenol (quercetin-3-glucuronide, myricetin-3-galactoside, gossypin, phlorizin, kaempferol, myricetin-3-arabinoside)-integrated zinc-silica core-shell Janus nanoparticles with UV protection, strength enhancement, and self-cleaning properties, is proposed. Polyphenols were utilized as sustainable precursors for synthesizing zinc-polyphenol complexes, which were then encapsulated within a silica shell to form a core-shell structure. Furthermore, Janus particles were created by introducing a bifunctional layer with half amine/carboxylic acid and half methyl terminals, imparting reactive hydrophilic and hydrophobic properties. Janus-coated textiles and leather exhibited significant attenuation of harmful UV radiation, with water contact angle measurements confirming improved water repellency. The coexistence of natural phenols and bifunctional groups within a material bolstered textile strength, fostering superior adhesion and markedly enhancing wash durability. This eco-friendly approach, utilizing waste-derived materials, presents a promising solution for sustainable textile engineering with enhanced performance in UV protection and water resistance, thereby contributing to the advancement of green nanotechnology in textile applications.

Tunable Dual Self-Healing Composite Coatings with Self-Assembled Structures Regulated by Janus Nanoparticles.

The durability of concrete structures can be enhanced in a convenient and permanent manner through the surface protection of cementitious materials with composite polymer coatings. However, polymer coatings are susceptible to various mechanical and physical deterioration in complex and variable environments. In this paper, the theory of polymer microstructure regulation was employed to improve the sustainability of the protective performance of composite coatings. The self-assembled core-shell structure regulated by amphiphilic Janus nanoparticles is employed to modify the tunable polystyrene acrylate-polysiloxane self-healing coatings. The results demonstrate that the adhesion strength of the prepared self-assembled coating reached 3.7 MPa, which is sufficient to resist the damage to the microstructure of cementitious materials caused by physical erosion, seepage, and ionic corrosion. The self-healing coating, regulated by Janus particles, exhibited a residual creep of only 57.03% and a maximum loss angle tangent of 0.381. Furthermore, the material exhibited a superior shape memory function due to the presence of strong hydrogen bonding. The regulated self-healing coating repaired the polymer structural damage under mechanical and thermal deformation by bridging and filling effects. The coating demonstrated a tensile strength recovery of up to 71.23% in a wetted state, accompanied by a rapid restoration of its electrochemical properties and corrosion resistance. Furthermore, the self-healing emulsion penetrates the substrate defects and forms numerous polymer crystalline particles that effectively fill the microcracks.

The Valence-Dependent Activity of Colloidal Molecules as Ice Recrystallization Inhibitors.

Inspired by advances in cryopreservation techniques, which are essential for modern biomedical applications, there is a special interest in the ice recrystallization inhibition (IRI) of the antifreeze protein (AFPs) mimics. There are in-depth studies on synthetic materials mimicking AFPs, from simple molecular structure levels to complex self-assemblies. Herein, we report the valence-dependent IRI activity of colloidal organic molecules (CMs). The CMs were prepared through polymerization-induced particle-assembly (PIPA) of the ABC-type triblock terpolymer of poly(acryloxyethyl trimethylammonium chloride)-b-poly(benzyl acrylate)-b-poly(diacetone acrylamide) (PATAC-b-PBzA-b-PDAAM) at high monomer conversions. Stabilized by the cationic block of PATAC, the strong intermolecular H-bonding and incompatibility of the PDAAM block with PBzA contributed to the in situ formation of Janus particles (AX1) beyond the initial spherical seed particles (AX0), as well as the high valency clusters of linear AX2 and trigonal AX3. Their distribution was controlled mainly by the polymerization degrees (DPs) of PATAC and PDAAM blocks. IRI activity results of the CMs suggest that the higher fraction of AX1 results in the better IRI activity. Increasing the fraction of AX1 from 27% to 65% led to a decrease of the mean grain size from 39.8% to 10.9% and a depressed growth rate of ice crystals by 58%. Moreover, by replacing the PDAAM block with the temperature-responsive one of poly(N-isopropylacrylamide) (PNIPAM), temperature-adjustable IRI activity was observed, which is well related to the reversible transition of AX0 to AX1, providing a new idea for the molecular design of amphiphilic polymer nanoparticle-based IRI activity materials.

Arrays of Bowl-Shaped Janus Particle Film with Structured Colors.

Structural colors generated via total internal reflection (TIR) using nanostructure-free micro-concave shapes have garnered increasing attention. However, the application of large micro-concave structures for structural coloration remains limited. Herein, a flexibly tunable structural color film fabricated by casting polydimethylsiloxane (PDMS) on an array of large poly(glycidyl methacrylate) (PGMA) bowl-shaped particles is reported. The resultant film exhibits tunable red to green structural colors with changing observation angles. Moreover, the color can be further tailored by altering the shape of the film itself. The incorporation of the PDMS layer not only facilitates a shift in the locus of TIR from the bottom surface to the top concave surface of the particles, thereby enabling the generation of structural color, but also confers enhanced flexibility to the film. Further decoration with silver nanoparticles imparts antimicrobial properties, yielding a novel antimicrobial coating material with structural colors. The simple and cost-effective strategy for the production of structural color films provides potential applications in antimicrobial coatings, enabling accessible and customizable structural coloration using big-size micro-concave particles.

Design of Janus Particles by Bipolar Electrochemistry at the Water–Organic Interface

Design of Janus Particles by Bipolar Electrochemistry at the Water–Organic Interface

DNA sensing based on aggregation of Janus particles using dynamic light scattering

BackgroundThe aggregation of isotropic particles through interparticle reactions poses a challenge in control due to the ability of all surfaces to bind to each other, rendering the quantitative detection of such interparticle reactions based on particle size difficult. Here, we proposed a novel detection scheme for DNA utilizing an assembly of Janus particles (JPs) employing dynamic light scattering (DLS). DNA molecules are tethered on one hemisphere of the JP, while the other hemisphere retains its hydrophobic properties. ResultsAggregation of JPs was induced by the sandwich hybridization of target DNA between them. The assembly of JPs was effectively monitored by the changes in hydrodynamic diameter detected by DLS, revealing that aggregation peaks at 2–3 particles and further reaction was hindered due to the inability of one hemisphere of the JP to interact with another JP. The target DNA demonstrated detectability at concentrations as low as several tens of pM to several nM using a digital sensing method. The two types of target DNA, such as simple (14 base pairs) and HIV-2 specific sequences (20 base pairs) were detectable at nM and pM levels, respectively. Moreover, we substantiated the robustness of our detection scheme through stoichiometric calculations based on an equilibrium model. The present detection mechanism was well explained based on the binding affinity of DNA hybridization. SignificanceThis detection method harnesses the anisotropic nature of JPs and represents the first detection approach based on aggregation. By altering the modification molecules on JPs to match target molecules, such as proteins and organic compounds, a wide range of versatile molecules can be detected using this scheme with high sensitivity. This underscores the broad applicability of the present method.

Biocompatible Janus microparticle synthesis in a microfluidic device.

Janus particles are popular in recent years due to their anisotropic physical and chemical properties. Even though there are several established synthesis methods for Janus particles, microfluidics-based methods are convenient and reliable due to low reagent consumption, monodispersity of the resultant particles and efficient control over reaction conditions. In this work a simple droplet-based microfluidic technique is utilized to synthesize magnetically anisotropic TiO2-Fe2O3 Janus microparticles. Two droplets containing reagents for Janus particle were merged by using an asymmetric device such that the resulting droplet contained the constituents within its two hemispheres distinct from each other. The synthesized Janus particles were observed under the optical microscope and the scanning electron microscope. Moreover, a detailed in vitro characterization of these particles was completed, and it was shown that these particles have a potential use for biomedical applications.

Controlled Surface Textures of Elastomeric Polyurethane Janus Particles: A Comprehensive Review.

Colloidal particle research has witnessed significant advancements in the past century, resulting in a plethora of studies, novel applications, and beneficial products. This review article presents a cost-effective and low-tech method for producing Janus elastomeric particles of varied geometries, including planar films, spherical particles, and cylindrical fibers, utilizing a single elastomeric material and easily accessible chemicals. Different surface textures are attained through strain application or solvent-induced swelling, featuring well-defined wavelengths ranging from sub-microns to millimeters and offering easy adjustability. Such versatility renders these particles potentially invaluable for medical applications, especially in bacterial adhesion studies. The coexistence of "young" regions (smooth, with a small surface area) and "old" regions (wrinkled, with a large surface area) within the same material opens up avenues for biomimetic materials endowed with additional functionalities; for example, a Janus micromanipulator where micro- or nano-sized objects are grasped and transported by an array of wrinkled particles, facilitating precise release at designated locations through wrinkle pattern adjustments. This article underscores the versatility and potential applications of Janus elastomeric particles while highlighting the intriguing prospects of biomimetic materials with controlled surface textures.

Discovering dynamic laws from observations: The case of self-propelled, interacting colloids.

Active matter spans a wide range of time and length scales, from groups of cells and synthetic self-propelled colloids to schools of fish and flocks of birds. The theoretical framework describing these systems has shown tremendous success in finding universal phenomenology. However, further progress is often burdened by the difficulty of determining forces controlling the dynamics of individual elements within each system. Accessing this local information is pivotal for the understanding of the physics governing an ensemble of active particles and for the creation of numerical models capable of explaining the observed collective phenomena. In this work, we present ActiveNet, a machine-learning tool consisting of a graph neural network that uses the collective motion of particles to learn active and two-body forces controlling their individual dynamics. We verify our approach using numerical simulations of active Brownian particles, active particles undergoing underdamped Langevin dynamics, and chiral active Brownian particles considering different interaction potentials and values of activity. Interestingly, ActiveNet can equally learn conservative or nonconservative forces as well as torques. Moreover, ActiveNet has proven to be a useful tool to learn the stochastic contribution to the forces, enabling the estimation of the diffusion coefficients. Therefore, all coefficients of the equationof motion of Active Brownian Particles are captured. Finally, we apply ActiveNet to experiments of electrophoretic Janus particles, extracting the active and two-body forces controlling colloids' dynamics. On the one side, we have learned that the active force depends on the electric field and area fraction. On the other side, we have also discovered a dependence of the two-body interaction with the electric field that leads us to propose that the dominant force between active colloids is a screened electrostatic interaction with a constant length scale. We believe that the proposed methodological tool, ActiveNet, might open a new avenue for the study and modeling of experimental suspensions of active particles.

Analysis of In Situ Electroporation Utilizing Induced Electric Field at a Wireless Janus Microelectrode.

In situ electroporation, a non-invasive technique for enhancing the permeability of cell membranes, has emerged as a powerful tool for intracellular delivery and manipulation. This method allows for the precise introduction of therapeutic agents, such as nucleic acids, drugs, and proteins, directly into target cells within their native tissue environment. Herein, we introduce an innovative electroporation strategy that employs a Janus particle (JP)-based microelectrode to generate a localized and controllable electric field within a microfluidic chip. The microfluidic device is engineered with an indium tin oxide (ITO)-sandwiched microchannel, where the electric field is applied, and suspended JP microelectrodes that induce a stronger localized electric field. The corresponding simulation model is developed to better understand the dynamic electroporation process. Numerical simulations for both single-cell and chain-assembled cell electroporation have been successfully conducted. The effects of various parameters, including pulse voltage, duration medium conductivity, and radius of Janus microelectrode, on cell membrane permeabilization are systematically investigated. Our findings indicate that the enhanced electric intensity near the poles of the JP microelectrode significantly contributes to the electroporation process. In addition, the distribution for both transmembrane voltage and the resultant nanopores can be altered by conveniently adjusting the relative position of the JP microelectrode, demonstrating a selective and in situ electroporation technique for spatial control over the delivery area. Moreover, the obtained differences in the distribution of electroporation between chain cells can offer insightful directives for the electroporation of tissues or cell populations, enabling the precise and targeted modulation of specific cell populations. As a proof of concept, this work can provide a robust alternative technique for the study of complex and personalized cellular processes.

Immune Cell-Based Microrobots for Remote Magnetic Actuation, Antitumor Activity, and Medical Imaging.

Translating medical microrobots into clinics requires tracking, localization, and performing assigned medical tasks at target locations, which can only happen when appropriate design, actuation mechanisms, and medical imaging systems are integrated into a single microrobot. Despite this, these parameters are not fully considered when designing macrophage-based microrobots. This study presents living macrophage-based microrobots that combine macrophages with magnetic Janus particles coated with FePt nanofilm for magnetic steering and medical imaging and bacterial lipopolysaccharides for stimulating macrophages in a tumor-killing state. The macrophage-based microrobots combine wireless magnetic actuation, tracking with medical imaging techniques, and antitumor abilities. These microrobots are imaged under magnetic resonance imaging and optoacoustic imaging in soft-tissue-mimicking phantoms and ex vivo conditions. Magnetic actuation and real-time imaging of microrobots are demonstrated under static and physiologically relevant flow conditions using optoacoustic imaging. Further, macrophage-based microrobots are magnetically steered toward urinary bladder tumor spheroids and imaged with a handheld optoacoustic device, where the microrobots significantly reduce the viability of tumor spheroids. The proposed approach demonstrates the proof-of-concept feasibility of integrating macrophage-based microrobots into clinic imaging modalities for cancer targeting and intervention, and can also be implemented for various other medical applications.

Adsorption characteristics of Janus tadpole polymers

The shape of Janus particles is directly connected to their adsorption behavior. Janus tadpole polymers offer a unique topological architecture that includes competition between entropic, enthalpic, and topological terms in the adsorption free energy; accordingly, non-trivial adsorption behavior patterns are expected. We study the surface adsorption of Janus tadpole polymers by means of Monte Carlo simulations, finding that, depending on which part of the tadpole polymers is preferentially adsorbing on the surface, very different types of behavior for both the adsorbed polymeric phase and of the brush arise. The adsorbed phase and the brush mutually influence each other, leading to a variety of phenomena such as nematic ordering of the adsorbed stiff tadpole tails and intriguing changes in the territoriality of adsorbed ring polymers on the surface. We analyze in detail our findings, revealing the mechanisms behind the organization and ordering, and opening up new possibilities to tune and control the structure of such systems.

Modified Janus silica-based sheets stable stimulus-responsive Pickering emulsion: An excellent recycling platform for tandem reaction

To accommodate the advancement of green chemistry and further enhance hydrogen utilization efficiency and organic compound conversion in reactions, a smart Pickering emulsion stabilized by modified Janus silica particles was successfully prepared for the tandem reaction of ammonia borane hydrolysis and organic hydrogenation reduction. The emulsion has been confirmed to possess high stability and rapid stimulus responsiveness. The high stability and large oil-water interface area of Pickering emulsions, along with their low energy demulsification method, provide an excellent reaction platform and catalyst in situ recovery strategy for tandem reactions. Moreover, the anisotropy of Janus particles facilitates the progression of tandem reactions, mitigating the waste associated with "sacrifice" mechanisms and averting hydrogen loss. Experimental results demonstrate that even when the molar amount of hydrogen released from ammonia borane is comparable to that of organic compounds, organic compounds still achieve a conversion rate of 99 %, with a hydrogen utilization efficiency 3–4 times higher than that of conventional two-phase systems. By simply adjusting the pH, the catalyst can be recovered in situ for the next cycle. Even after 5 cycles, a high conversion rate of organic compounds is maintained.

Integrating machine learning with -SAS for enhanced structural analysis in small-angle scattering: applications in biological and artificial macromolecular complexes.

Small-Angle Scattering (SAS), encompassing both X-ray (SAXS) and Neutron (SANS) techniques, is a crucial tool for structural analysis at the nanoscale, particularly in the realm of biological macromolecules. This paper explores the intricacies of SAS, emphasizing its application in studying complex biological systems and the challenges associated with sample preparation and data analysis. We highlight the use of neutron-scattering properties of hydrogen isotopes and isotopic labeling in SANS for probing structures within multi-subunit complexes, employing techniques like contrast variation (CV) for detailed structural analysis. However, traditional SAS analysis methods, such as Guinier and Kratky plots, are limited by their partial use of available data and inability to operate without substantial a priori knowledge of the sample's chemical composition. To overcome these limitations, we introduce a novel approach integrating -SAS, a computational method for simulating SANS with CV, with machine learning (ML). This approach enables the accurate prediction of scattering contrast in multicomponent macromolecular complexes, reducing the need for extensive sample preparation and computational resources. -SAS, utilizing Monte Carlo methods, generates comprehensive datasets from which structural invariants can be extracted, enhancing our understanding of the macromolecular form factor in dilute systems. The paper demonstrates the effectiveness of this integrated approach through its application to two case studies: Janus particles, an artificial structure with a known SAS intensity and contrast, and a biological system involving RNA polymerase II in complex with Rtt103. These examples illustrate the method's capability to provide detailed structural insights, showcasing its potential as a powerful tool for advanced SAS analysis in structural biology.

Hydrodynamic behavior of Janus particles in a finite inertial flow

Hydrodynamic behavior of Janus particles in a finite inertial flow is studied numerically using the lattice Boltzmann method (LBM) in the range of Reynolds number 0.05 ⩽ Re⩽ 10 and swimming parameter −3 ⩽ β ⩽ 3. Some results are validated by comparing with the existing results. The effects of Re, β on the hydrodynamic behavior of Janus particles are analyzed. The results show that the velocity of a pusher (a type of Janus particles) monotonically increases with the increase of Re, while the velocity of a puller (another type of Janus particles) exhibits a non-monotonic change. At high Re, the puller is unstable and presents a lateral displacement, while the pusher remains stable. The power consumption for the pusher and puller, the hydrodynamic efficiency for the pusher increase monotonically with increasing Re, while the hydrodynamic efficiency for the puller exhibits a non-monotonic change. At low Re, the power consumption and hydrodynamic efficiency of Janus particles exhibit symmetry with the variation of surface velocity distribution. This symmetry is disrupted with the increase of Re, similar to the velocity changing with the surface angle.

Evolution Kinetics of Stabilizing Pickering Emulsion by Brush-Modified Janus Particles: DPD Simulation and Experimental Insights.

In the present study, we report the evolution of stabilizing Pickering emulsions using brush-modified Janus particles (JPs), utilizing the dissipative particle dynamics (DPD) simulation technique. Our results are subsequently corroborated with experimental findings. Each JP has one-half of the hydrophobic surface, with the other half embedded with hydrophilic polymer brushes grown via atom transfer radical polymerization (ATRP). Our generic simulation model analyzes the chemical kinetics of polymer brush growth on one-half of the initiator-embedded microparticle (MP) surface, resulting in the formation of JP. This involves evaluating monomer conversion and reaction rates. Our results exhibit a substantial influence of the number of JPs, grafted brush density, and brush length on oil-in-water emulsion stability. We studied the evolution kinetics and stability of emulsion formation by analyzing the growth of average domain size and corresponding scaling functions up to a late time limit. This study aims to clarify the connection between the size, quantity, and functionality of JPs and the stability of Pickering emulsions.

Construction of Polysiloxane Induced Multilevel Bowl-shaped Janus Particles for Fabrication of Photoluminescent, Enhanced, Heat-insulative Poly(styrene-co-butyl acrylate) Latex Coating

Silica-based nanoparticles (SNPs) are highly regarded as advantageous nanofillers for composite coating, owing to their high surface area, robust mechanical properties, chemical stability, and adaptability for surface modification. Recent studies have unveiled the potential photoluminescence of SNPs induced by intrinsic defect sites, eliminating the need for additional fluorescein molecules. However, the inadequate quantum yield and complex preparation processes for generating defect sites within SNPs have constrained their broader applications. Herein, we propose a facile method to prepare Janus silicon-based nanoparticles with a hierarchical bowl-shaped structure (JHSNPs) through the emulsification of methyltriethoxysilane hydrolysis and condensation products, coupled with the capillary force during nanoparticle formation. The distinctive structure enhances the formation of dioxasilyrane (=Si(O2)) and silylene (=Si:) defects, thereby exhibiting strong blue photoluminescence. The JHSNPs then serve as nanofillers for commonly used poly(styrene-co-butyl acrylate) (SA) waterborne coatings, significantly enhancing their mechanical properties, abrasion resistance, and UV radiation resistance compared to the original SA coatings. Moreover, with just a 1% addition of JHSNPs, the composite coating exhibits visible fluorescence intensity, conferring the self-detecting monitoring properties for external scratches. Due to the hierarchical air-entrapping void structure, JHSNPs composite coatings demonstrate excellent thermal isolation performance, with a 22% reduction in thermal conductivity. The design of JHSNPs opens new avenues to expand the versatility of silica-based nanoparticles in composite coatings, especially in the optical, safety, and energy-saving fields.

A novel synthesis method of magnetic Janus particles for wastewater applications

HypothesisMagnetic particles are widely used in many adsorption and removal processes. Among the many types of magnetic colloids, magnetic Janus particles offer significant possibilities for the effective removal of several components from aqueous solutions. Nevertheless, the synthesis of structures integrating different types of materials requires scalable fabrication processes to overcome the limitations of the available methodologies. Herein, we hypothesized a fabrication process for dual-surface functionalized magnetic Janus particles. ExperimentsThe primary silica particles with surface-attached amine groups are further asymmetrically modified by iron oxide nanoparticles, exploiting Pickering emulsion and electroless deposition techniques. The dual surface functionality of the particles is designed for its versatility and demonstrated in two wastewater-related applications. FindingsWe show that our design can simultaneously remove chromium (VI) and phenol from aqueous solution. The fabricated magnetic-responsive Janus particles are also an effective adsorbent for genomic Deoxyribonucleic acid (DNA) and show superior performance to commercial magnetic beads. Thus, this study provides a novel platform for designing magnetic Janus particles with multifunctional surfaces for wastewater treatment applications.

Self-diffusiophoretic propulsion of a spheroidal particle in a shear-thinning fluid

Shear-thinning viscosity is a non-Newtonian behaviour that active particles often encounter in biological fluids such as blood and mucus. The fundamental question of how this ubiquitous non-Newtonian rheology affects the propulsion of active particles has attracted substantial interest. In particular, spherical Janus particles driven by self-diffusiophoresis, a major physico-chemical propulsion mechanism of synthetic active particles, were shown to always swim slower in a shear-thinning fluid than in a Newtonian fluid. In this work, we move beyond the spherical limit to examine the effect of particle eccentricity on self-diffusiophoretic propulsion in a shear-thinning fluid. We use a combination of asymptotic analysis and numerical simulations to show that shear-thinning rheology can enhance self-diffusiophoretic propulsion of a spheroidal particle, in stark contrast to previous findings for the spherical case. A systematic characterization of the dependence of the propulsion speed on the particle's active surface coverage has also uncovered an intriguing feature associated with the propulsion speeds of a pair of complementarily coated particles not previously reported. Symmetry arguments are presented to elucidate how this new feature emerges as a combined effect of anisotropy of the spheroidal geometry and nonlinearity in fluid rheology.

Modulating the Transmission of Light Using Asymmetric Janus Particles

AbstractThe ability to manipulate the absorption, scattering, or reflectivity of light using synthetic materials has inspired innovations in nano‐ and micro‐materials for applications ranging from geoengineering to display optics. Asymmetric materials, like Janus particles, offer one solution to meet the needs of such technologies, as composition and geometry can be optimized to maximize directional optical properties in response to magnetic and/or electric fields, light, or electrostatic charge. In this work, a gram‐scale synthesis is applied to generate Janus matchstick particles comprising a gold head with a silica rod. Conditions are explored and optimized to elicit rotation of these matchstick particles under an alternating current (AC) electric field with varying field strength and frequency to maximize particle alignment. While only modest changes in transmission (≈8%) are observed over the visible spectral region with a bare silica rod, the application of an absorbing element increased transmission changes up to ≈23% demonstrating their utility as color‐changing materials. Experimental results are supported by theory and computation and highlight an important first step in activating directional optical effects in these materials which can be optimized for future adaptive technologies.