Anisotropic Janus Research Articles

Synthesis of Janus Polydiacetylene Sensor Particles with Thermochromism and Solvatochromism Properties

The first report is presented on the fabrication of anisotropic Janus polydiacetylene (PDA) microparticles with dual colorimetric properties. Spherical proto‐PDA particles are initially created by drying an emulsion containing 10,12‐pentacosadiynoic acid (PCDA) monomers, followed by UV polymerization. By heating an aqueous dispersion of these PDA particles, the unpolymerized PCDA within the PDA particles is liquefied, inducing partial phase separation and eventually leading to the formation of a Janus morphology composed of proto‐PDA and deriv‐PDA bulbs. Notably, each bulb of the Janus particles undergoes a blue‐to‐red transition under thermal stress during the Janus formation process, with subsequent UV irradiation triggering a reversible red‐to‐blue transition. This reversibility is attributed to the formation of new self‐assembled PCDA domains from residual PCDA monomers within the particles. Interestingly, each bulb of the Janus PDA particles exhibits distinct solvatochromic properties. These findings suggest significant potential for Janus PDA particles in advanced sensing technologies, particularly as solvent sensors with enhanced sensitivity and an expanded detection range.

Design and electrospinning synthesis of red luminescent-highly anisotropic conductive Janus nanobelt hydrogel array films

A new strategy for the preparation of conductive hydrogels by a simple method with high anisotropic conductivity is proposed.

Synthesis of anisotropic Janus composite particles based on polystyrene/urushiol- lanthanum chelate polymer.

To expand the potential applications of raw lacquer, snowman-like polystyrene (PS)-urushiol lanthanum (ULa) Janus composite particles were synthesized by emulsion swelling-assisted protrusion from PS/ULa core-shell composite microspheres. The morphology and chemical composition of the PS/ULa composite microspheres and the PS-ULa Janus composite particles were investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR). The PS-ULa Janus particles were compartmentalized into two parts, each with a different morphology and chemical composition. Results showed that the intact ULa shell with appropriate thickness is a crucial factor for controllable swelling, and the thickness of the PS/ULa core-shell composite microsphere could be controlled by polymerization temperature. This anisotropic Janus particle exhibits potential applications in orienting materials, such as directional catalysis.

Tough and anisotropic Janus hydrogel for tendon injury repair with controlled release of bFGF in tendon microenvironment

To address the high complexity and challenging nature of large-scale tendon injury repair, an innovative Janus structured hydrogel patch (JAHP@bFGF) was designed in this study. The patch combines microenvironmental responsiveness with efficient repair function, aiming to optimise and accelerate the tendon healing process. The outer layer is a PVA/SA/Na3Cit hydrogel with excellent mechanical properties, protein resistance, and low friction, which provides firm support to the tendon and reduces adhesions to ensure the recovery of gliding function. The inner layer of TCSB@bFGF microgel responds intelligently to changes in the microenvironment, precisely regulates the release of bFGF, promotes cell proliferation and migration, accelerates tissue regeneration, and has high adhesion strength and antimicrobial properties, which significantly reduces the risk of postoperative infection. Experimental results show that JAHP@bFGF significantly optimises the healing process, accelerates the repair speed and improves the repair quality under simulated large-scale tendon injury conditions. The unique Janus surface design and the intelligent drug release function, in synergy, not only bring new hope to patients with large-scale tendon injuries, but also provide an important reference for the application of biomedical materials in the repair of complex tissues, which heralds the arrival of the era of more efficient and personalised tendon repair.

Chemically-Driven Autonomous Janus Electromagnets as Magnetotactic Swimmers.

An electromagnet is a particular device that takes advantage of electrical currents to produce concentrated magnetic fields. The most well-known example is a conventional solenoid, having the form of an elongated coil and creating a strong magnetic field through its center when it is connected to a current source. Spontaneous redox reactions located at opposite ends of an anisotropic Janus swimmer can effectively mimic a standard power source, due to their ability to wirelessly generate a local electric current. Herein, we propose the coupling of thermodynamically spontaneous redox reactions occurring at the extremities of a hybrid Mg/Pt Janus swimmer with a solenoidal geometry to generate significant magnetic fields. These chemically driven electromagnets spontaneously transform the redox-induced electric current into a magnetic field with a strength in the range of μT upon contact with an acidic medium. Such on-board magnetization allows them to perform compass-like rotational motion and magnetotactic displacement in the presence of external magnetic field gradients, without the need of using ferromagnetic materials for the swimmer design. The torque force experienced by the swimmer is proportional to the internal redox current, and by varying the composition of the solution, it is possible to fine-tune its angular velocity.

Chemically‐Driven Autonomous Janus Electromagnets as Magnetotactic Swimmers

AbstractAn electromagnet is a particular device that takes advantage of electrical currents to produce concentrated magnetic fields. The most well‐known example is a conventional solenoid, having the form of an elongated coil and creating a strong magnetic field through its center when it is connected to a current source. Spontaneous redox reactions located at opposite ends of an anisotropic Janus swimmer can effectively mimic a standard power source, due to their ability to wirelessly generate a local electric current. Herein, we propose the coupling of thermodynamically spontaneous redox reactions occurring at the extremities of a hybrid Mg/Pt Janus swimmer with a solenoidal geometry to generate significant magnetic fields. These chemically driven electromagnets spontaneously transform the redox‐induced electric current into a magnetic field with a strength in the range of μT upon contact with an acidic medium. Such on‐board magnetization allows them to perform compass‐like rotational motion and magnetotactic displacement in the presence of external magnetic field gradients, without the need of using ferromagnetic materials for the swimmer design. The torque force experienced by the swimmer is proportional to the internal redox current, and by varying the composition of the solution, it is possible to fine‐tune its angular velocity.

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.

Sticky and Strain-Gradient Artificial Epineurium for Sutureless Nerve Repair in Rodents and Nonhuman Primates.

The need for the development of soft materials capable of stably adhering to nerve tissues without any suturing followed by additional damages is at the fore at a time when success in postoperative recovery depends largely on the surgical experience and/or specialized microsuturing skills of the surgeon. Despite fully recognizing such prerequisite conditions, designing the materials with robust adhesion to wet nerves as well as acute/chronic anti-inflammation remains to be resolved. Herein, a sticky and strain-gradient artificial epineurium (SSGAE) that overcomes the most critically challenging aspect for realizing sutureless repair of severely injured nerves is presented. In this regard, the SSGAE with a skin-inspired hierarchical structure entailing strain-gradient layers, anisotropic Janus layers including hydrophobic top and hydrophilic bottom surfaces, and synergistic self-healing capabilities enables immediate and stable neurorrhaphy in both rodent and nonhuman primate models, indicating that the bioinspired materials strategy significantly contributes to translational medicine for effective peripheral nerve repair.

Formation of three-dimensional (3D) Self-Assembled Clusters of Anisotropic Janus Particles in Microgravity

Abstract The self-assembly of colloidal particles enables the creation of complex materials with tailored properties. This process, particularly involving anisotropic particles, can lead to the formation of structurally unique and complex assemblies that are not achievable with isotropic particles. On Earth, gravitational forces limit the investigation of these particles’ intrinsic motion and interactions, posing significant challenges to comprehensively understanding the fundamental forces governing their interactions. To overcome these limitations, this study, in collaboration with NASA’s Glenn Research Center (GRC), employs the Light Microscopy Module (LMM) aboard the International Space Station (ISS) to observe the self-assembly phenomena of anisotropic particles under microgravity conditions. Our investigation shows that anisotropic Janus particles with their distinctive properties can spontaneously organize into ordered structures under microgravity. This directional interaction among anisotropic particles is expected to enable control over assembly processes, forming three-dimensional (3D) clustered structures that are unattainable on Earth. Thus, this study not only advances our understanding of particle self-assembly in microgravity but also opens new avenues for synthesizing materials with novel functionalities through the unique assembly of anisotropic colloids.

On-Demand Sequential Release of Dual Drug from pH-Responsive Electrospun Janus Nanofiber Membranes toward Wound Healing and Infection Control.

Drugs against bacteria and abnormal cells, such as antibiotics and anticancer drugs, may save human lives. However, drug resistance is becoming more common in the clinical world. Nowadays, a synergistic action of multiple bioactive compounds and their combination with smart nanoplatforms has been considered an alternative therapeutic strategy to fight drug resistance in multidrug-resistant cancers and microorganisms. The present study reports a one-step fabrication of innovative pH-responsive Janus nanofibers loaded with two active compounds, each in separate polymer compartments for synergistic combination therapy. By dissolving one of the compartments from the nanofibers, we could clearly demonstrate a highly yielded anisotropic Janus structure with two faces by scanning electron microscopy (SEM) analysis. To better understand the distinctive attributes of Janus nanofibers, several analytical methods, such as X-ray diffraction (XRD), FTIR spectroscopy, and contact angle goniometry, were utilized to examine and compare them to those of monolithic nanofibers. Furthermore, a drug release test was conducted in pH 7.4 and 6.0 media since the properties of Janus nanofibers correlate significantly with different environmental pH levels. This resulted in the on-demand sequential codelivery of octenidine (OCT) and curcumin (CUR) to the corresponding pH stimulus. Accordingly, the antibacterial properties of Janus fibers against Escherichia coli and Staphylococcus aureus, tested in a suspension test, were pH-dependent, i.e., greater in pH 6 due to the synergistic action of two active compounds, and Eudragit E100 (EE), and highly satisfactory. The biocompatibility of the Janus fibers was confirmed in selected tests.

On the Interfacial Assembly of Anisotropic Amphiphilic Janus Particles

AbstractIt has been shown both theoretically and experimentally that amphiphilic Janus particles are the most effective solid surfactants to stabilize interfaces. In most cases, the Janus particles investigated have uniform morphologies with Janus boundaries dividing the particle into halves. However, there are many examples of Janus particles where the hydrophilic and hydrophobic domains are not equally distributed. The effects of this uneven domain distribution on the mechanism and kinetics of Janus particle assembly, and final equilibrium state are not well‐understood. Dynamic pendant drop tensiometry offers a means to probe both the equilibrium assembly and the kinetics and mechanism of assembly. Here, the interfacial kinetics and assembly of spherical anisotropic Janus particles are investigated using dynamic pendant drop tensiometry. Systematic studies quantifying the time‐dependent interfacial behavior as a function of Janus particle morphology, chemical composition, particle concentration, and NaOH and HCl concentration are performed. These studies shed light on the assembly mechanism of more complex Janus particle morphologies and highlight their effectiveness as interface stabilizers.

Synthesis of Anisotropic Magnetic Polymeric Janus Particles by In Situ Separation of Magnetic Nanoparticles in a Microfluidic Device.

Magnetic Janus particles have been studied extensively for medical and biological applications owing to their controllable mobility in fluid media. In this work, we report a novel microfluidic device designed for the synthesis of magnetically anisotropic Janus particles made of poly(ethylene glycol) diacrylate and embedded with magnetic iron oxide nanoparticles. Our method consists of a droplet generation step followed by magnetic separation using an external magnetic field and ultraviolet polymerization. The synthesized particles exhibit a monodisperse size distribution with a standard deviation of less than 3.5%, which is among the best size distributions obtained in the literature for magnetic Janus particles. The anisotropic magnetic property of the particles enable them to rotate about their own axes in the presence of an external magnetic field, introducing another degree of freedom to their motion. This microfluidic technique is simple, one-step, and versatile, offering control over the size distribution to synthesize magnetically anisotropic Janus particles.

Anisotropic Multitentacle Janus Particles Synthesized by Selective Asymmetric Growth.

Anisotropic colloidal particles with asymmetric morphology possess functionally rich heterogeneous structures, thus offering potential for intricate superstructures or nanodevices. However, it is a challenge to achieve controlled asymmetric surface partitioned growth. In this work, an innovative strategy is developed based on the selective adsorption and growth of emulsion droplets onto different regions of object which is controlled by wettability. It is found that the emulsion droplets can selectively adsorb on the hydrophilic surface but not the hydrophobic one, and further form asymmetric tentacle by the interfacial sol-gel process along its trajectory. Janus particles with an anisotropic shape and multitentacle structure are achieved via integration of emulsion droplet (soft) and seed (hard) templates. The size and number of tentacles exhibit tunability mediated by soft and hard templates, respectively. This general strategy can be expanded to a variety of planar substrates or curved particles, further confirming the correlation between tentacle growth and Brownian motion. Most interestingly, it can be employed to selectively modify one region of surface partitioned particles to achieve an ABC three-component Janus structure.

Non-Classical Self-Assembly of Anisotropic Magneto-Organosilica Janus Particles Possessing Surfactant Properties and the Field-Triggered Breakdown of Surface Activity and Amphiphilic Properties.

Using colloidal particles as models to understand processes on a smaller scale is a precious approach. Compared to molecules, particles are less defined, but their architecture can be more complex and so is their long-range interaction. One can observe phenomena that are unknown or much more difficult to realize on the molecular level. The current paper focuses on particle-based surfactants and reports on numerous unexpected properties. The main goal is creating an amphiphilic system with responsiveness in surface activity and associated self-organization phenomena depending on applying an external trigger, preferably a physical field. A key step is the creation of a Janus-type particle characterized by two types of dipoles (electric and magnetic) which geometrically stand orthogonal to each other. In a field, one can control which contribution and direction dominate the interparticle interactions. As a result, one can drastically change the system's properties. The features of ferrite-core organosilica-shell particles with grain-like morphology modified by click chemistry are studied in response to spatially isotropic and anisotropic triggers. A highly unusual aggregation-dissolution-reaggregation sequence w as discovered. Using a magnetic field, one can even switch off the amphiphilic properties and use this for the field-triggered breaking of multiphase systems such as emulsions.

Anisotropic dispersion promoting and passivation protecting of CA@JNs@Zn2+ Janus nanosheets on epoxy anticorrosive coatings

Defects in the curing process of epoxy coatings tend to deteriorate the anticorrosion performance of the coatings. An important way to enhance the anticorrosion performance of epoxy coatings is to add flaky fillers. In this paper, anisotropic Janus nanosheets (JNs) were prepared and modified by cardanol (CA) and Zn2+. Then, the obtained CA@JNs@Zn2+ Janus composite nanosheets were introduced into epoxy coatings. When the content of CA@JNs@Zn2+ is 0.2 %, the mechanical properties and corrosion resistance of the coating were effectively improved. The tensile strength of 0.2 %-CA@JNs@Zn2+/EP coating is 79 % higher than that of pure epoxy coating. The EIS analysis showed that the low-frequency impedance of the coating remained as high as 16.45 Gohm·cm2 after 35 days of immersion, and remained above 10 Gohm·cm2 during the whole immersion period, which demonstrating the optimal corrosion resistance. This paper provides a theoretical basis for the preliminary application of Janus material in the field of anticorrosion, and the prepared composite coatings are expected to be used for anticorrosion in harsh environment.

Spatially isolated magnetic-mesoporous units in one anisotropic Janus nanoparticle for rapid and selective extraction of uranium

Iron oxide with superparamagnetic property and mesoporous silica with large surface areas are both important to design multifunctional sorbents, and magnetic-mesoporous nanoparticles of asymmetric morphology may make full use of their advantages. To address this, spatially isolated magnetic-mesoporous units in one anisotropic Janus nanoparticle with abundant amidoxime (AO) groups (AO-Fe3O4@C&mSiO2) was synthesized for rapid and selective extraction of uranium. Chemically and structurally anisotropic AO-Fe3O4@C&mSiO2 was composed of one AO functionalized mesoporous silica nanorods and a carbon coated Fe3O4 nanoparticle, which displayed excellent surface area (139.9 m2 g−1) and saturation magnetization (28.79 emu g−1). Thus, AO-Fe3O4@C&mSiO2 showed fast adsorption kinetics for reaching adsorption equilibrium within 30 min, and then they were able to be collected in 3.0 s under an external magnetic field. The maximum and spontaneous adsorption capacity for uranyl ions was obtained by fitting thermodynamic data through Langmuir model at 298 K was 62.12 mg g−1, and AO-Fe3O4@C&mSiO2 achieved the highest uptake amount and removal rate of almost 100% towards uranium in the presence of competitive ions. Meanwhile, the results from ten regeneration cycles confirmed the high service lifetime of AO-Fe3O4@C&mSiO2. This work not only demonstrates a strategy for preparing multifunctional sorbents with anisotropic structure but also provides a method for selective uranium extraction.

Plant protein nanogel–based patchy Janus particles with tunable anisotropy for perishable food preservation

AbstractJanus particles with anisotropic surfaces possess considerable potential for biological functionalization. However, little is known about the effect of surface anisotropy of Janus particles on the shelf life of perishable food. Herein, plant protein–based nanogels prepared by acylated rapeseed protein isolate (ARPI) are exploited as novel building blocks to decorate the surface of latex particles for Janus particle synthesis. The surface anisotropy of patchy latex particles can be facilely tailored via the suspension polymerization of the Pickering emulsion using ARPI nanogels as stabilizers. The surface distribution of ARPI nanogel on latex particles can be controlled by varying the aqueous phase conditions, and thus, the tunable hydrophilic–lipophilic balance (viz., Janus balance) varied from 0.78 to 1.76 for resulting patchy latex particles. Patchy latex particles with varied Janus balance were further investigated for the effects of their anti‐perishable coatings on perishable fruit preservation. The anisotropic patchy latex particles can act as a novel type of antibacterial agent to inhibit Ascomycota microorganisms’ growth on the surface of fruits and reduce the dehydration and respiration of fruits, all of which devote to a lengthened shelf life while being safe. Furthermore, it is found that the patchy latex particle with a spatial pattern of a hydrophobic area on its surface occupying 51.3% (Janus balance = 0.95) extends the shelf life of perishable food more effectively than that of other spatial arrangements. Overall, the exploration of anisotropic Janus particles offers an alternative strategy to preserve perishable food without using antimicrobial agents.

Renewable pickering emulsion system based on bifunctional materials for highly efficient fuel oil desulfurization without stirring

The mass transfer resistance atliquid (oil)-liquid (extractant)interface seriouslylimits the reaction rate and desulfurization efficiency in extraction-catalytic oxidative desulfurization (ECODS), and the catalyst is difficult to be recycled in the homogeneous system. Herein, we demonstrated a renewable Pickering emulsion system with enlarged interfacial contact area to overcome the mass transfer resistance. The bifunctional materials were designed based on Janus graphene oxide (GO) 2D-sheets, amino-modified SBA-15 (NH2-SBA-15) mesoporous microspheres and H3PW12O40 (HPW), as both catalysts and emulsion stabilizers to establish the catalytic emulsion system. Excellent amphiphilicity was endowed by the anisotropic Janus structure of prepared materials, which could convert the oil/extractant bi-phase into a stable Pickering emulsion. The interfacial contact area was skillfully enlarged in emulsion due to formed micro emulsion droplets and empty channels between the droplets, and the catalyst could be easily recycled by centrifugation. Besides, the unique properties of catalyst including large specific surface area, adequate exposed catalytic active sites and high pore volume could also shorten the reaction path and facilitate the rapid diffusion of reactants and products. This opens the door to the application of Pickering emulsion in ECODS fields based on the design of bifunctional materials.

A novel gradient structured nanofiber and silver nanowire composite membrane for multifunctional air Filters, oil water Separation, and health monitoring flexible wearable devices.

Particular matter (PM), oily wastewater, and microorganisms (e.g., bacteria) have caused serious environmental, health, and safety issues. However, the development of multifunctional filtration materials to address these problems remains a great challenge. Here, we present a series of gradient structured air filters by simply spray coating poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers on nylon mesh, followed by silver nanowires (AgNWs). Interestingly, it is found that the ANF-6 air filter is an anisotropic Janus membrane with asymmetric wettability and translucency. The as-prepared ANF-6 air filter exhibits excellent water vapor transmission rate (4447.92 ± 184.78g/(m2. d)), PM filtration (96.42 ± 0.64% for PM0.3), photothermal (79.6°C under 1sun in 150s), thermal insulation, antibacterial, and oil water separation. Additionally, the obtained ANF-6 air filter was impregnated with carbon black (CB) dispersion and served as flexible pressure sensors to monitor human respiration rate (17 times/min) and wrist pulse rate (80 times/min). The gradient structured PVA-co-PE nanofibers and AgNWs network provides excellent air filtration, oil water separation, and sensitivity performance for the sensors. These results provide a new scheme for designing multifunctional filtration materials and wearable pressure sensors in the application of air filtration, oil water separation, and wearable electronics for monitoring human health.

A multifunctional and long-term waterborne anti-corrosion coating with excellent ‘hexagonal warrior’ properties

Environmentally friendly waterborne coatings tend to form polar pathways due to more hydrophilic groups, resulting in poor coating corrosion resistance and reduced coating service life. The anisotropic Janus is used as a filler for waterborne epoxy (WEP) coatings to reduce the number of hydrophilic groups and improve interface compatibility by cross-linking the hydrophilic end with the resin; at the same time, the hydrophobic groups are used to improve the water resistance of the coating. In this paper, we synthesized sheet-like silica Janus (JNS) materials by interface-induced self-assembly via sol–gel reaction in oil-in-water emulsions to prepare novel water-based JNS/WEP anticorrosion coatings. The excellent corrosion resistance of JNS/WEP coatings is explained by the fact that the hydrophilic end of JNS reduces internal defects in the coating and enhanced interfacial interaction; the hydrophobic end improves the water resistance of the coating. Similarly, the physical barrier advantage of flake JNS is brought into play to reduce the high availability of water and oxygen, inhibit electrochemical corrosion on the surface of carbon steel and form a passivation film; the active group at the hydrophilic end of JNS can be chelated with Fe3+ for active protection by synergistic. Among them, immersed in 3.5 wt% NaCl solution for 130 days, the impedance modulus of 1.0 % JNS/WEP coating is 2 orders of magnitude higher than that of WEP coating, up to 2.59 × 1010 O cm2. Therefore, it exhibits outstanding anti-corrosion performance under multiple synergistic protection.