Size Of Microcapsules Research Articles

Tuning alginate-bentonite microcapsule size and structure for the regulated release of P. putida Rs-198

In this study, different sizes of microcapsules with alginate and bentonite as natural macromolecular materials were prepared to investigate the release property of Pseudomonas putida Rs-198. The characteristics of three microcapsules were evaluated by SEM, FTIR, TG-DSC, XRD and wall thickness. The sizes of three microcapsules (MA, MB, and MC) were 1270.50, 831.79 and 42.52 μm, respectively. First, the encapsulation efficiency of three MA, MB, and MC microcapsules were 82.20%, 90.41%, and 85.84%, respectively. Second, the contact angles of MA and MB samples were similar, while smaller microcapsules MC have higher contact angle (85.05°), indicating poor hydrophilia and decreasing the swelling degrees. Third, the release cumulant of Rs-198 and macromolecule BSA linear stage was fitted to self-established mathematic model. Results show that the microcapsule size had a considerably positive effect on release detail. The large microcapsule possessed strong leak-tightness for Rs-198 as a slow-release microbial agent. Furthermore, the porosity of microcapsules determined their swelling and release and may affect bacterial growth and survival. In conclusion, the Rs-198 microcapsule with different sizes will be pertinently selected based on the characteristics of agricultural production requirements.

THE INFLUENCE OF CORE - SHELL RATIO ON CHARACTERISTICS OF MICROCAPSULES CONTAINING CINNAMON ESSENTIAL OIL APPLIED TO AROMATHERAPEUTIC TEXTILES

Microencapsulation is one of the techniques to prepare the functional textiles. In this paper the essential cinnamon oil loaded microcapsules were prepared by solvent evaporation method. In the microencapsulation process, the core - shell ratio was changed by altering the cinnamon oil content in four levels of 0.15, 0.25, 0.35 and 0.45 g while the other components remained unchanged. The microcapsule characteristics including shape and morphology, size and size distribution, microencapsulation efficiency in dependence on the core-shell ratio were investigated. The antimicrobial capacity and the fragrance durability of interlock knitted fabric coated with the elaborated microcapsules were evaluated. The results showed that cinnamon oil was microencapsulated successfully in the spherical microcapsules. When the cinnamon oil content increased, the microcapsule size decreased and the size distribution became broader, the microcapsules were more porous and more aggregate, the fragrance intensity of the fabric treated with microcapsules increased while the activity against E. coli bacteria decreased. According to the results, the microcapsules elaborated with 0.15 g of cinnamon oil was recommended for the treatment of interlock cotton knitted fabric to apply in aroma and antimicrobial textiles.

Effects of Different Environment-Friendly Gibberellic Acid Microcapsules on Herbicide Injury of Wheat.

Environmentally friendly microcapsules are becoming more and more widely used due to the increasing demand for environmental safety in pesticides. To compare the impact of differences in wheat herbicide phytotoxicity of different gibberellic acid microcapsule suspensions, two microcapsule suspensions were separately formulated using the phase transfer method and the in situ polymerization method, and the key performance indicators are the size of microcapsules and the degree of encapsulation. Meanwhile, through field trials, the pharmacological and detoxification effects of different types of microcapsule suspensions on the herbicide methyldisulfuron in wheat fields were compared. The microcapsule suspension was prepared by the phase transfer method and the particle sizes D10, D50, and D90 are 0.990, 2.136, and 5.201 μm, respectively; the microcapsule suspension was prepared by the in situ polymerization, the particle sizes D10, D50, and D90 are 4.365, 8.547, and 16.782 μm, respectively. The encapsulation rate of the microcapsules prepared by the phase transfer method and the in situ polymerization method was 86.9% and 91.2%, being higher than 80%, the national standard for capsules. Meanwhile, the release rate conforms to first-order release kinetics in 0–4 days and zero-order release kinetics in 5–28 days. The plot trials' result showed that the detoxification effect of the microcapsules prepared by the in situ polymerization method was significantly better than the detoxification effect of the microcapsules prepared by the phase transfer method and the control agent. The growth index of wheat was higher than that of the untreated check after using the agent.

Influence of acid and alkali reaction system on the morphology and thermal properties of paraffin@SiO2 phase change microcapsules for heat storage

Phase change materials are preferred in the field of thermal energy storage in low-medium temperature. Paraffin@SiO2 microcapsules were prepared by a sol–gel method at an acid and alkali reaction system. The field emission scanning electron microscope, Fourier transform infrared spectroscope, differential scanning calorimetry, and thermogravimetric analyzer were adopted to investigate the effect of the acid and alkali reaction system on the morphology, latent heat, and thermal stability of PA@SiO2 microcapsules. In the acid reaction system, the particle size and latent heat of PA@SiO2 microcapsules are in the range from 15 to 30 μm and from 132 to 174 J/g, respectively. However, comparing with the acid reaction system, there was a remarkable reduction in the particle size and latent heat of microcapsules prepared in the alkali reaction system. The initial weightlessness temperatures of PA@SiO2 microcapsules were 40 °C higher than that of paraffin, indicating that the SiO2 shell was beneficial to the microcapsule structure.

Fluidization dynamics in an impinging-jet-driven bioreactor for artificial liver system

Liquid–solid fluidized beds have been applied in the field of bioreactors for artificial liver systems. This paper uses a coupling method of computational fluid dynamics and discrete element method to numerically study the fluidization dynamics of an impinging-jet-driven bioreactor. A long tube is placed at the centerline of a cylindrical container in the bioreactor. The liquid is discharged toward the bottom of the container to form an impinging jet to drive the fluidization process of the microcapsules. The bioreactor's bed expansion height, porosity distribution, and interaction between the liquid and microcapsules are analyzed at different microcapsule densities, sizes, and flow rates. It is found that the bed expansion is proportional to the inlet flow rate and inversely proportional to the microcapsule density and size. The distribution of porosity indicates overall even fluidization, except for a dead region near the bottom periphery of the bioreactor. The dead region shrinks with increasing flow rate and expands with increasing density and size of the microcapsules. It is found that the interaction of microcapsules may play an essential role in the variations of the dead region. Understanding the fluidization dynamics of the impinging-jet-driven bioreactor is crucial in bioreactor design and optimization to improve its performance.

Microencapsulation of wheat germ oil by external gelation and its oil release characteristics

In microencapsulation, composition of wall materials defines the characteristics of microcapsules, their targeted use, and bioavailability of the core material. Sodium alginate (SA) is a good candidate as a cold method to produce microcapsules, but its high cost, sodium foot prints, and digestive intolerance are the constrains. In the present study, SA was partially substituted with starch (S), pectin (P), and whey (W) to encapsulate wheat germ oil (WGO). Encapsulation efficiency was highest at 20% and 30% replacement of SA. The angle of repose was highest for S. Oil release studies were conducted in hexane, simulated gastric and intestinal fluid (SGF and SIF) without enzymes. SA with S had highest mean release in hexane (60.07%), SFG (21.11%), and SIF (72.25%) followed by P and W. The amount of oil released was lower in lower core to coating ratios and substitution of SA with polymers caused an increase in oil release. Novelty impact statement Encapsulation efficiency was highest at 20% and 30% replacement of sodium alginate. The addition of pectin increased the mean size of microcapsules of wheat germ oil. Oil released percentage in simulated gastric and intestinal fluid was less in lower core to coating ratios.

Performance-Based Evaluation of Healing Efficiency on Mechanical Properties of Self-Healing Cementitious Materials Incorporated with PMMA/Epoxy Microcapsule.

In this study, based upon the investigation of its effect on workability and the mechanical property of cementitious materials, the Box–Behnken design was adopted to establish models describing self-healing performance on mechanical properties of cementitious materials with polymethylmethacrylate (PMMA)/epoxy microcapsule in terms of healing rate of peak strength (Y1), the recovery rate of peak strength (Y2), the healing rate of Young’s modulus (Y3), the recovery rate of Young’s modulus (Y4), the healing rate of peak strain (Y5), and recovery rate of peak strain (Y6). This was performed under the influence of the four factors, including microcapsule size (X1), microcapsule content (X2), pre-loading (X3), and curing age (X4). The results showed the four factors significantly affect the healing rate and recovery rate of the peak strength, Young’s modulus, and peak strain, except the healing rate on peak strain. Moreover, the interaction between the factors showed some influence as well. The numerically optimised values of X1, X2, X3, and X4 are 203 nm, 5.59%, 43.56%, and 21 days, respectively, and the self-healing cementitious materials with desirable mechanical characteristics (Y1 63.67%, Y2 145.22%, Y3 40.34%, Y4 132.22%, Y5 27.66%, and Y6 133.84%) with the highest desirability of 0.9050 were obtained. Moreover, the porosity of the specimen confirmed the healing performance of PMMA/epoxy microcapsules in cementitious materials.

Influence of wall material combination on the lipid oxidation of the hazelnut oil microcapsules

AbstractHazelnut oil (HO) is important in terms of fatty acid composition and bioactive substances. Although there are a few studies on hazelnut oil encapsulation, there is limited research on the investigation of different wall material combinations for hazelnut oil microencapsulation and oxidative stability of the microcapsules. This study aimed to evaluate the effects of different wall material combinations (gum Arabic, sodium caseinate, whey protein, gelatine, modified starch “Em-Cap” and pea protein with maltodextrin at a ratio of 1:9,w/w, respectively) on the oxidation degree of hazelnut oil microcapsules produced by spray drying. The feed emulsions used for microcapsule production were analyzed for emulsion stability (ES) and particle droplet size. The encapsulation efficiency (EE), moisture content, bulk density, particle size and total yield of hazelnut oil microcapsules were analyzed. Peroxide and p-Anisidine values were investigated during 15 days of storage at 50 °C. While the highest encapsulation efficiency, emulsion and oxidative stability were obtained for modified starch/maltodextrin (Em-Cap/MD), the lowest yeild was obtained for gelatine/maltodextrin (GE/MD) with the highest oxidation rate. Among the six wall material combinations evaluated, the modified starch (Em-Cap) performed best, with the highest encapsulation efficiency and lowest lipid oxidation rate. The results showed that the oxidative stability of hazelnut oil microcapsules was enhanced by combining different wall materials to increase the shelf life, which is reflected at the level of the food industry.

Experimental and numerical investigation on the effect of core-shell microcapsule sizes on mechanical properties of microcapsule-based polymers

In this study, the effect of various microcapsule sizes on the mechanical properties of microcapsule-based polymeric materials was investigated using the finite element method and validated with experimental outcomes. Specimens containing 5wt. % of microcapsules were fabricated to calculate the elastic modulus, and maximum tensile stress, and to validate numerical results. To consider the error, five tests were performed for all samples, and results were reported on average. The average errors between the numerical outcomes and experimental results were 4.74% and 5.35% for maximum tensile stress and elastic modulus, respectively. The coaxial electrospraying method was used for synthesizing microcapsules made of alginate (shell) and epoxy (core). A scanning electron microscope (SEM) was used to calculate the diameter of the capsules. To develop an empirical model for the average microcapsule diameter (AMD) and carry out the optimization process, response surface methodology (RSM) with central composite design was used. Also, analysis of variance was employed to validate the accuracy of the model. The effects of three parameters, including voltage, needle size, and the distance between the tip of the needle to the collector, on average microcapsule diameter, were investigated. The empirical model was validated by a confirmation run, and the determined error (1.93%) between the predicted and experimental results indicates the precision of the model. The numerical study indicated that microcapsule-based self-healing polymers containing smaller microcapsules tolerate higher stresses. However, the effect of the microcapsules’ size on the elastic modulus of a representative volume element was negligible.

Microfluidic Fabrication and Thermal Properties of Microencapsulated N-Hexadecane with a Hybrid Polymer Shell for Thermal Energy Storage.

In this study, a strategy based on microfluidic method is developed toward a facile fabrication of phase change material microcapsules with uniform and controllable particle size as well as high encapsulation ratio and thermal stability. N-hexadecane, as a phase change material, was successfully encapsulated by a hybrid shell of poly (methyl methacrylate) and polyurea. The fabrication process includes the following three steps: (1) Formation of oil-in-water droplets with uniform micron size in the microfluidic chip; (2) formation of the first polyurea shell to encapsulate droplets by fast interfacial polymerization when the droplets pass through the coiled transport microchannel; and (3) completion of free radical polymerization of methyl methacrylate inside the microspheres by heating to form the hybrid microcapsule shell. The average size, encapsulation ratio, and phase change enthalpy of microcapsules changed by varying the flow rate of the dispersion phase and raw material composition. The highest melting enthalpy of 222.6 J g−1 and encapsulation ratio of 94.5% of the microcapsule were obtained when the flow rates of the continuous and dispersion fluids were 600 μL min−1 and 24 μL min−1, respectively. It is shown that the phase change material microcapsules were stable after 50 heating/cooling cycles.

Spray-Drying Encapsulation of the Live Biotherapeutic Candidate Akkermansia muciniphila DSM 22959 to Survive Aerobic Storage.

Akkermansia muciniphila is regarded as a promising next-generation probiotic or live biotherapeutic candidate. Effective delivery strategies must be developed to ensure high enough viability of the probiotic strain throughout its industrial formulation, distribution chain, shelf-life, and, ultimately, the host’s gastrointestinal tract, where it should exert its beneficial effect(s). Among the possible methodologies, spray-drying is considered industrially attractive regarding its costs, efficiency, and scalability, with the due parameter customization. In this study, spray-drying was explored as a one-step process to encapsulate A. muciniphila DSM 22959, testing the drying settings and three different dairy-based matrices. Microcapsule morphology and size was assessed, and viability throughout storage at 4 or 22 °C and simulated gastrointestinal passage was determined. Akkermansia muciniphila microencapsulation by spray-drying, using 10% skim milk and inlet/outlet temperatures of 150/65 °C, is effective in terms of viability stabilization, both during prolonged aerobic storage and exposure to simulated gastrointestinal passage. Akkermansia muciniphila viability was maintained at around 107 CFU/g up to 28 days at 4 °C under aerobic conditions with viability losses inferior to 1 log reduction. This methodology provides the necessary conditions to efficiently deliver the recommended dose of live A. muciniphila in the human gut as a live biotherapeutic product.

Computational Modelling for the Effects of Capsular Clustering on Fracture of Encapsulation-Based Self-Healing Concrete Using XFEM and Cohesive Surface Technique

The fracture of microcapsules is an important issue to release the healing agent for healing the cracks in encapsulation-based self-healing concrete. The capsular clustering generated from the concrete mixing process is considered one of the critical factors in the fracture mechanism. Since there is a lack of studies in the literature regarding this issue, the design of self-healing concrete cannot be made without an appropriate modelling strategy. In this paper, the effects of microcapsule size and clustering on the fractured microcapsules are studied computationally. A simple 2D computational modelling approach is developed based on the eXtended Finite Element Method (XFEM) and cohesive surface technique. The proposed model shows that the microcapsule size and clustering have significant roles in governing the load-carrying capacity and the crack propagation pattern and determines whether the microcapsule will be fractured or debonded from the concrete matrix. The higher the microcapsule circumferential contact length, the higher the load-carrying capacity. When it is lower than 25% of the microcapsule circumference, it will result in a greater possibility for the debonding of the microcapsule from the concrete. The greater the core/shell ratio (smaller shell thickness), the greater the likelihood of microcapsules being fractured.

Pre-Pilot Scale Microencapsulation of Phase Change Materials for Thermal Energy Storage Applications

. Most of the researcher has attempted for the encapsulation of phase change materials in small scale for the thermal storage applications. However, energy conversion in field applications require enormous quantity of thermal energy storage materials. In this paper, a pre-pilot scale is developed for encapsulating of various binary mixtures using an in-situ polymerization technique.DSC, TGA, FTIR, XRD, and FE-SEM were used to delineate the thermal properties of obtained microcapsules in order to identify shape, mean size, functional groups, crystalline state, and weight loss of distinct microcapsules. The results show that the synthesized microcapsules were regular in shape and smooth and well encapsulated around cores. The thermal properties of different microcapsules are 34.9 ℃, 95.3 kJ/kg and 35.6 ℃, 98.5 kJ/kg resultant to microencapsulation of 75% Stearic acid (SA) + 25% Capric acid (CA) and 63% Capric acid (CA) + 37% Palmitic acid (PA),respectively. The encapsulation efficiencies were 78.2% and 73.09%. The yieldof the products are attained ~82%.

Preparation and characterization of Sparassis latifolia β-glucan microcapsules

Abstract In order to effectively protect the biological activity of Sparassis latifolia β-glucan, improve its stability, and realize its high-value utilization, single-factor test and orthogonal test were carried out to optimize the microencapsulation conditions of S. latifolia β-glucan prepared using spray drying method. The β-glucan microcapsules were characterized by scanning electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and laser particle size analyzer. The results showed that the optimal microencapsulation conditions were as follows: maltodextrin and whey protein with a mass ratio of 1:2, core and wall material with a mass ratio of 1:2, and monoglyceride and core material with a mass percentage of 0.3. Under these conditions, the powder yield and embedding rate of β-glucan microcapsules were 47.32 ± 0.58% and 86.76 ± 1.19%, respectively. The preparation technique was proved to be stable. The β-glucan microcapsules were spherical particles, with the characteristics of a smooth surface, no cracks. The particle size of microcapsules was smaller, and its Dv (50) was 8.43 µm. The distribution of microcapsules was more uniform, and its uniformity was 0.503. The good embedding performance and high thermal stability can effectively protect the biological activity of the core material.

Thermoresponsive semi-interpenetrating gelatin-alginate networks for encapsulation and controlled release of scent molecules

Plant-based meats, which are nutritious foods from non-animal sources, provide clues for addressing the negative externalities associated with conventional meat production. Interest in plant-based meat has increased and is driving the rapid growth of its market. Plant-based meat should be equipped with a temperature-dependent scent release system similar to the scent release mechanism of conventional meat, to deliver a desirable meat-like flavor to consumers and obtain higher market acceptance. In this study, we prepared thermoresponsive gelatin-alginate hybrid hydrogels to control the release of scent molecules. The polymer network of gelatin-alginate hydrogels was reinforced by a semi-interpenetrating network (sIPN). sIPN formation conferred resistance to external stimuli, such as shear force, swelling, and temperature, resulting in a sustained release of the meat scent. In addition, controlled size microcapsules fabricated from the same composition via an electrostatic extrusion process showed a sustained release pattern of the loaded scent at 70 °C, and the scent release rate was precisely controlled within an approximately 2-fold range by adjusting the alginate concentration. These observations suggest the potential use of edible biological macromolecules as food additives that can control the release of scent molecules from the plant-based meat during cooking.

Characterization of polyurea microcapsules synthesized with an isocyanate of low toxicity and eco-friendly esters via microfluidics: Shape, shell thickness, morphology and encapsulation efficiency

There are some studies on the synthesis of polyurea microcapsules. However, there is hardly a case where both green solvents and non-toxic isocyanates are used, especially in microfluidics. In this work, an environmentally friendly chemical system of interfacial polymerization (isocyanate: HDB-LV; solvent: octyl salicylate or dibutyl adipate) is tested for the first time to produce polyurea microcapsules. The size of microcapsules is calibrated at 78 μm by microfluidics to quantitatively analyze the relationships among shell thickness, encapsulation efficiency and isocyanate concentrations. The influences of solvent types and reactant concentrations on the shape, morphology and shell thickness of microcapsules are studied. Esters with low water miscibility and low amine concentrations (lower reaction rate) are crucial for the formation of spherical microcapsules. An ester with high water miscibility can diffuse into the continuous phase during encapsulation, which results in broken microcapsules. A high concentration of amine can probably cause cross-linking not only at the interface but also inside the droplet template, which leads to microcapsule deformation. A linear relationship is observed between the shell thickness of microcapsules and the isocyanate concentration. Overall, a high encapsulation efficiency (more than 90%) for octyl salicylate is achieved with polyurea microcapsules.

The Effect of Complex Emulsifier on the Structure of Tung Oil and Phenolic Amides Containing Microcapsules and Its Anti-Fouling and Anti-Corrosion Performances

In this study, the urea-formaldehyde (UF)-tung oil solution of phenolic amide (PA) microcapsules to realize anti-fouling and anti-corrosion integration was synthesized by the in situ polymerization method. The compounds and structures were optimized by investigating six kinds of different emulsifiers. The results showed that high-core-content and narrow-particle-size-distribution microcapsules could be synthesized with sodium dodecyl benzene sulfonate (SDBS)/polyvinyl alcohol (PVA), and the core content of the microcapsules was 75 wt% at microcapsule sizes from 24.07 to 71.33 µm. The results of self-healing coatings showed that when the content of microcapsules in the coating exceeded 10 wt%, the healing agent released from the scratched surface could cover the naked metal effectively, which could pass a 7 day neutral salt spray test without rust at the scratched area. A sufficient dose anti-fouling agent can be provided to prevent diatoms and mussels from adhering. The present work shows that the complex emulsifier can better control the particle size distribution and microstructure of the microcapsules, and the admixture of the microcapsules into the resin epoxy coating can realize excellent anti-corrosion and anti-fouling functions.

Synthesis and characterization of layered double hydroxides hybrid microcapsules for anticorrosion via self-healing and chloride ion adsorption

Self-healing and corrosion resistance microcapsule (S/CMC) was fabricated by solvent evaporation method with tung oil (TO) as core, layered double hydroxides (LDH) as corrosion inhibitor and ethyl cellulose (EC) as wall. The average particle size of microcapsule increased with the increase of LDH content when LDH was less than 20 wt%. LDH component was present in the wall of S/CMC by surface loading, the chlorine adsorption performance of microcapsule in neutral environment was superior to that in alkaline environment. LDH was hybridized in EC to form stable wall structure. The LDH embedded in hybrid wall captured chloride ion by surface adsorption and ion exchange to improve the corrosion resistance of steel bar. This study provides a solution for the compatibility of anti-corrosion and self-healing technology, and provides a new perspective for the anti-corrosion application of microcapsule.

Sustained release /self-cleaning zein-based hybrid microcapsule leather finishing material

In this study, zein, Pluronic F127, artemisia argyis essence, and butyl titanate are used to craft zein-based hybrid microcapsule by interfacial condensation and anti-solvent precipitation approach. Morphology and structure of the hybrid microcapsule were characterized by SEM, UDFM, FTIR, XRD and XPS, separately. Sustained release behavior and self-cleaning performance of the hybrid microcapsule were also observed. The results indicated that the average size of zein-based hybrid microcapsule was approximately 6 μm with stable structure. It is worth noting that, this double-shelled microcapsule possessed sustained release behaviors, only 9% of AAE was released after 9 h. Significantly, the TiO2 in the outer shell endows the composite coating with superior self-cleaning performance. The as-prepared hybrid microcapsule finishing material is a good candidate for bio-based functional coatings applied in various fields including leather, paper, painting, cosmetics and so on.

One-pot efficient preparation of microcapsules based on photopolymerization for self-healing coatings

Self-healing microcapsules are currently one of the most promising functional materials due to their excellent performance. The preparation of self-healing microcapsules via photopolymerization is quite attractive considering its efficiency and environmental-friendliness. However, the influence of the preparation process and shell-formation materials on the formation and the morphology of microcapsule have not been systematically researched. This work combines photopolymerization technology and solvent evaporation to prepare microcapsule, and comprehensively explores the influence of process conditions and shell-formation materials on the microcapsules. Two preparation processes, UV-SR (photopolymerization first and then solvent removal) and SR-UV (solvent removal first and then photopolymerization), have been employed to prepare microcapsules. The SR-UV method is more suitable for preparing microcapsules with high core content and spherical core-shell morphology. The particle size distribution of microcapsules is related to the shear strength during initial emulsion preparation, and the size of microcapsules can be effectively controlled. At the same time, the effect of the shell-formation materials is also systematically studied. The method is universal for the preparation of microcapsules based on commercial UV-curable prepolymers, but the introduction of UV-curable monomers may lead to the transformation of microcapsules from core-shell structure to multi-core structure. Microcapsules can be uniformly dispersed in water-borne epoxy, and the coating based on microcapsules exhibits excellent self-healing properties.