Influence Of Shell Thickness Research Articles

Enhancing Mechanical Characteristics of PETG Carbon Fiber Composite through Various Shell Thickness in FDM Processing

The utilization of PETG (Polyethylene Terephthalate Glycol) carbon fiber composites in Fused Deposition Modelling (FDM) processes has gained significant attention due to their enhanced mechanical properties compared to traditional PETG filaments. This study focuses on investigating the impact of varying shell thickness on the mechanical characteristics of PETG carbon fiber composites fabricated through FDM. The objective is to optimize the shell thickness to achieve superior mechanical performance while maintaining printing efficiency. A series of PETG carbon fiber composites with different shell thicknesses were manufactured using an FDM 3D printer. Mechanical tests, including tensile strength, flexural strength, and impact resistance, were conducted to evaluate the performance of the fabricated specimens. Additionally, micro-structural analysis was performed to understand the influence of shell thickness on the interfacial bonding between PETG matrix and carbon fibers. Preliminary results indicate that increasing shell thickness positively affects the mechanical properties of PETG carbon fiber composites. Tensile and flexural strength show a noticeable improvement with an increase in shell thickness, attributed to enhanced interlayer adhesion and improved load-bearing.

Thermally enhanced nanocomposite phase change material slurry for solar-thermal energy storage

This paper investigates the photothermal conversion performance of an innovative heat transfer fluid containing nano-encapsulated phase change material (PCM) with metallic shell materials in a solar thermal energy storage system. The influences of shell thickness, core size, shell material type, PCM mass and shell volume concentrations on the thermal performance of the heat storage medium are investigated and compared. The results show that the heat transfer rates of water-based Ag, Au, Cu and Al nanofluids are 6.89, 5.86, 7.05 and 6.99 W, respectively, while slurries formed by adding paraffin@Ag, Au, Cu and Al nano capsules to pure water enhance heat transfer by 6.18, 13.38, 10.8 and 11.33 %, respectively. The metallic nanoparticle-based shell materials further augment the temperature and energy storage gains by enhancing the solar radiation capture capability of the heat storage medium. Specifically, depending on the mass concentration of PCM, the storage capacity of paraffin@Cu slurry is augmented by up to 290 %. As the shell thickness of the Ag particles also decreases from 8 to 2 nm, it augments the slurry's storage ability for thermal energy by 7 %. The enhancement in the dimensions of the nano capsules, however, causes the surface area-to-volume ratio (SA:V) to reduce the photothermal conversion of the slurry by clustering. Therefore, the thermal energy storage behaviour of the Paraffin@Cu slurry is diminished by 5 % as the core size enhances from 10 to 40 nm. Further, the augmentation in the volume concentration of Al particles in the shell surprisingly reduces the thermal energy storage by 5 %. Finally, paraffin-based solid PCM is also experimentally tested for validation of the specific heat capacity model at various wind speeds and solar radiation.

Regulating hollow structure of CL-20 microspheres using microjet droplet technology to enhance safety and combustion performance

Hollow energetic microspheres have attracted great attention in the field of materials due to their wide application potential. However, scalable, simple, and low-cost production methods have not been achieved yet. In this study, using nitrocellulose (NC) as a binder, hollow and porous hollow CL-20 microspheres were prepared by the assist of microjet droplet technology. The effects of receiving liquid temperature, solution concentration, and solvent type on the morphology, particle size, shell thickness, and pore size of the CL-20 microspheres were systematically investigated. Furthermore, the influences of shell thickness and pore size on the dispersibility, crystal structure, thermal decomposition, mechanical sensitivity, and combustion behavior of CL-20 microspheres were further studied. The results showed that precise control over the shell thickness and pore size of CL-20 microspheres could be achieved by adjusting the process parameters. Compared to raw CL-20, the CL-20 microspheres exhibited excellent dispersibility and improved thermal and safety performance (raw CL-20 vs CL-20 microspheres, 40.3° vs 27.1° ∼ 29.1°; 240.4℃ vs 241.1 ∼ 246.2℃; 2 J vs 25 ∼ 32.5 J). Ignition experiments demonstrated that the hollow and porous hollow structures significantly enhanced the combustion flame of CL-20, shortened the burning time, and thereby improved energy release efficiency. This preparation method is simple and efficient, providing a new approach for the fabrication of multi-structured hollow energetic microspheres.

Influence of Shell Thickness on the Photophysical Properties of Core—Shell Perovskite Nanocrystals

AbstractCore–shell perovskite nanocrystals (NCs) have emerged as a promising class of materials for optoelectronic applications due to their unique properties and stability. Although much research has been conducted on the shell growth mechanism and properties of the core–shell NCs, little is known about the role of shell thickness in determining their optical properties. Herein, a heteroepitaxial method is employed to prepare a series of core–shell FAPbBr3/CsPbBr3 NCs with different shell thicknesses. Through temperature‐dependent photoluminescence measurement, it is found that the electronic structure of core–shell FAPbBr3/CsPbBr3 NCs evolves from quasi‐type‐II to type‐I with the increase in shell thickness. This abnormal transition can be attributed to the thickened gradient alloy layer FA1‐xCsxPbBr3, which effectively relieves the lattice mismatch and releases strain in the NCs, resulting in variations in the bandgap between the core and the shell. Furthermore, the biexciton Auger lifetimes in these samples exhibit a non‐monotonic dependence on shell thickness, indicating the electronic structure transition. These results provide valuable insights into the relationship between shell thickness, electronic structure, and optical properties in core–shell perovskite NCs, which may offer guidance for the design of high‐performance optoelectronic devices.

Au@SnO2 Core@Shell Nanocrystals for Sustainable Environmental Purifications

The search for versatile catalysts for sustainable environmental purifications has been a challenging yet very important research topic especially in the post pandemic era. Core@shell nanocrystals composed of metal core and semiconductor shell have received significant attention as both photocatalysts and chemical catalysts for practical use in organic dyes degradation and bacterial disinfection. This work reports the synthesis of Au@SnO2 core@shell nanocrystals with controllable shell thicknesses. Under light illumination, Au@SnO2 can function as photocatalysts to decompose organic dyes (rhodamine B, RhB) and inactivate E. coli. Because of the band alignment between Au and SnO2, an enhanced photocatalytic activity was achieved on Au@SnO2. Time-resolved photoluminescence spectroscopic analysis was conducted to explore the influence of shell thickness on the interfacial charge dynamics of Au@SnO2 in order to establish the correlation with the resultant photocatalytic performance. On the other hand, the peroxidase mimics features of Au and SnO2 endowed Au@SnO2 with the capability of performing the disinfection of E. coli under darkness conditions. By combining the phtotocatalytic capacity with the peroxidase mimics features, Au@SnO2 demonstrated sustainable activity toward E. coli disinfection under both irradiation and darkness conditions.

Influence of shell thickness on the thermal stability and melting-like behavior of Al@Fe core–shell nanoparticles from atomistic simulations: a structural and dynamic description

Core–shell nanoparticles (CSNPs) are a class of functional materials that have received important attention nowadays due to their adjustable properties by a controlled tuning of the core or shell. Understanding the thermal response and structural properties of these CSNPs is relevant to carrying out an analysis regarding their synthesis and application at the nanoscale. The present work is aimed to investigate the shell thickness effect on thermal stability and melting behavior of Al@Fe CSNPs by using molecular dynamics simulations. The results are discussed considering the influence of the Fe shell on the Al nanoparticle and analyzing the effect of different shell thicknesses in Al@Fe CSNPs. In general, calorific curves show a smooth energy decline for temperatures greater than room temperature for different shell thicknesses and sizes, corresponding to the inward and outward atomic movement of Al and Fe atoms, respectively, that produce a mixed Al–Fe nanoalloy. Here, the thermal stability of the Al@Fe nanoparticle is gradually lost passing to a liquid-Al@solid-Fe configuration and reaching a mixed Al–Fe state by an exothermic mechanism. Combining quantities of the atomic diffusion and structural identification, a stepped structural transition of the system is subsequently observed, where the melting-like point was estimated. Furthermore, it is observed that the Al@Fe CSNPs with greater stability are obtained with a thick shell and a large size. The ability to control shell thickness and vary the size opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.

Adaptability of polyurea microcapsules loaded with octyl salicylate for sunscreen application: influence of shell thickness of microfluidic-calibrated capsules on UV absorption efficiency

The common chemical ultraviolet (UV) filters such as octyl salicylate that are used in sunscreen cream may cause irritation and other unknown medical conditions. One possible route to avoid the direct contact of UV filters with human skin is to enclose those filters in microcapsules. In this study, microcapsules with a size calibrated at 78 μm via microfluidics but with different shell thicknesses (0.4 to 2.5 μm) are used for the first time, to study the influence of shell thickness of microcapsules on the UV absorption efficiency. The results show that the shell thickness of microcapsules has no obvious influence on the UV absorption efficiency. Besides, a rough model based on the Beer–Lambert law is used to compare the experimental results.

Study the influence of shell thickness in bimetallic Ag core&Au shell configurations integrated in bare Si PN junction solar cells

The effect of the gold layer thickness of Ag core&Au shell configurations on the performance of the bare Si n-type layer of a PN junction solar cell was explored. The different forms of Ag core&Au shell configurations were formed via pulsed laser ablation method of Ag and Au plate using second harmonic generation (SHG) of Nd:YAG laser wavelength at 530 nm with 0.61 J/cm2 energy flounce and various pluses repetition rate 350-500. The integrating of Ag core&Au shell configurations in n-type of bare PN Si junction was accomplished via pluses laser illumination of bare PN junction substrate. The photovoltaic results of formed solar cells showed strong dependence on Au shell thickness. Tangible enhancement was observed in the performance of bare Si solar cells after inserting core–shell configuration with specific shell thickness owning to the broadband absorption of plasmonics nanoparticles and the high values of specific surface area.

Decoding the Electro-Chemo-Mechanical Coupling in Core-Shell Nanoparticles for PEFC Catalyst Layers

Core-shell nanostructured catalysts possess a novel architecture where a major portion (core) of the nanoparticle is composed of cheaper materials such as Cobalt, Palladium, Copper, etc., with only a small portion (shell) being the expensive Platinum (Pt) thus enabling the reduction of Pt loading in the catalyst layer. These core-shell nanocatalysts are known to exhibit better mass activity than their monolithic counterparts. In this context, tuning the core can result in a change in both mechanical and geometrical properties, and in turn, can influence the stability. Specifically, designing an interface with surface stresses that makes the structure of the nanostructured catalysts resistant to dissolution would be pivotal towards achieving enhanced durability in PEFC systems. The lattice mismatch between the core and shell is a key intrinsic parameter that governs a transition towards a thermodynamically metastable state. In this work, the mesoscale underpinnings of such metastability on the underlying electro-chemo-mechanical coupling and the resulting influence on degradation-performance interactions will be analyzed. Further, the role of molar volumes and elastic moduli of such core-shell pairs on the evolution of stress states and degradation landscape will be investigated. Design criteria including the influence of shell thickness in protecting against degradation will be delineated.

Influence of Shell Thickness on Durability of Ru@Pt Core-Shell Catalysts for Reformate PEM Fuel Cells

For the use of polymer electrolyte membrane fuel cells (PEMFCs) in heavy duty applications, on-site generation of hydrogen rich gas by reforming hydrocarbons or methanol are a suitable alternative to pure H2 due to higher availability and higher energy density of hydrocarbon fuels [1]. The so-called reformate contains in addition of H2 also CO, which is a catalyst poison. PtRu alloys are the most promising catalysts for PEM fuel cells operated with reformate due to their high CO-tolerance [2]. It is known that the less noble Ru is unstable in acidic PEMFC conditions and is lowering the durability of the membrane electrode assembly (MEA) by dissolution and crossing over through the membrane to the cathode [3]. Ru dissolution and crossover result in a decreased CO-tolerance on the anode and a lower activity of the cathode towards oxygen reduction due to Ru blocking the Pt surface of the cathode catalyst [4]. To prolong the lifetime and CO-tolerance of reformate PEMFCs, the stability of the anode catalysts must be improved. One approach is nano-structuring the catalysts by encapsulating the less noble Ru-core with a Pt-shell. In doing so, the corrosion resistant Pt-shell supposes to protect the Ru-core from dissolution and thus mitigates the Ru crossover phenomenon.In this work, the influence of the Pt-shell thickness on the stability and performance of the Ru@Pt catalysts is investigated. Two catalysts with varying Pt-shell thicknesses were synthesized on Vulcan XC72R carbon via a two-step polyol. The catalyst with the thinner Pt-shell is called Ru@1Pt and with the thicker shell Ru@2Pt. The as-synthesized catalysts were physically characterized by XRD, ICP-OES, TEM and EDS. A representative EDS map of Ru@1Pt is shown in fig. 1a. The physical characterization of the obtained catalysts unveils a Ru@Pt core-shell structure with crystalline hcp Ru and fcc Pt. To further investigate the catalysts electrochemically, MEAs were manufactured using Ru@Pt catalysts as anodes and commercial membranes and cathode catalysts. An accelerated stress test (AST) was developed to target Ru dissolution by potential cycling and was applied to investigate and compare the stability of the catalysts. The MEAs were electrochemically characterized by cyclic voltammetry, CO-stripping and U-I curves before, during and after the AST. Post-mortem cross-section STEM analysis of the stressed cells were performed to evaluate the elemental composition and morphology of the anode and cathode after the stress test.During the AST, CO-stripping on the Ru@1Pt anode showed a peak shift to higher potentials, indicating a decrease in CO-tolerance due to Ru loss. By contrast, on the Ru@2Pt anode, the peak shifted to lower potentials implying a stronger promoting influence of Ru. On the cathode side, CV measurements before and after the AST revealed a double layer increase and a decrease in the HUPD. This change implies the poisoning of Pt with Ru and were more pronounced for Ru@1Pt compared to Ru@2Pt. As seen by the CO-stripping and CV results, the Ru dissolution and crossover was more severe for Ru@1Pt than for Ru@2Pt. Hence, a higher fuel cell performance loss was observed for the cell with Ru@1Pt in H2, as can be seen in fig. 1b. In addition, further U-I curves were measured under varying reformate conditions to identify the influence of CO on the cell performance. Cross-section EDS maps of the stressed MEAs were used to evaluate the Ru dissolution and its distribution in the different layers of the MEA. A higher Ru:Pt ratio was found on the cathode for the cell with Ru@1Pt compared to a cell with Ru@2Pt, which further verifies a higher degree of Ru crossover for the catalyst with the thinner Pt-shell. The above findings could evidence that the shell thickness plays a significant role in the corrosion resistance of core-shell reformate anode fuel cell catalysts.

The influence of shell thickness on coke resistance of core-shell catalyst in CO2 catalytic reforming of biomass tar

The development of catalysts with resistance to sintering and coke deposition is the key to tar cracking during biomass gasification technology. In this work, the core-shell catalysts with mesoporous and microporous silica-coated nickel nanoparticles were prepared for the CO2 reforming of toluene as a model compound for biomass tar. The influence of thickness of SiO2 shell layer on catalyst activity, coke and sintering resistance of the catalysts in the CO2 reforming of toluene was explored. Appropriate increasing in the thickness of the silica shell can significantly increase the specific surface area, pore volume and the interaction between core and shell of the catalysts, which can further improve the reactivity and coke resistance ability. However, excessive increase in shell thickness can lead to a drastic decrease in the specific surface area and pore volume of the catalyst, resulting in significant coke deposition. The [email protected]2-4 catalyst showed the highest catalytic activity of toluene conversion of around 50% within 300 min, stability H2/CO ratio of 0.25∼0.3 and durability of 26 h lifetime in the CO2 reforming of toluene. Overall, the optimization of the silica shell thickness can improve the reactivity and coke resistance ability of [email protected]2.

Parametric investigation of the assembled bolt-connected buckling-restrained brace and performance evaluation of its application into structural retrofit

In this paper, the hysteresis performance of an assembled bolt-connected buckling-restrained brace (AB-BRB) is experimentally discussed by a parametric study, and five changing factors are selected to analyze the corresponding influence in static behaviors. The deformation modes of core plates are compared, the critical points of hysteresis curves are analyzed, and six static indices for hysteresis responses are assessed. Afterwards, the seismic evaluations of AB-BRB applied into structural retrofit are conducted, based on an aged 3-span-3-story and 5-span-10-story reinforced concrete frame. The numerical model is established and verified for both local AB-BRB and integral frame structure, and the simulation details as well as selection strategies are suggested during the process. The nonlinear time history analyses, incremental dynamic analyses and seismic fragility analyses are all performed, and three dynamic indices, three limit states, three fractile probabilities, three comparing conditions and two intensity levels are well discussed for assessment, before and after retrofitting, respectively. In general, the influences of shell thickness are less than shell height, and a larger gap clearance may transfer the deformation pattern into end-wave modes. Less bolt number may affect the assembly operation and global buckling capacity, which proves the effectiveness of bolt design equation in a sense. Bolt number contributes greatly to the macro hysteresis trends, and less tightening bolts may weaken the retraining property, accompanied with the bolt-slippage occurrence under huge vertical thrusts transferred from core plates. The seismic indices for each ground motion are below limitations and are more uniform with less discreteness after retrofitting with AB-BRB. The structural capacity can be guaranteed safely, and the damage degree of the integrated system can be controlled with the application of AB-BRB, illustrating the apparent retrofitting superiority in performance enhancement and providing reference for the follow-up research of AB-BRB in the earthquake-prone areas.

Numerical Modeling of the Mechanical Reliability of Multicoated Nanoencapsulated Phase‐Change Materials with Improved Thermal Performance

Nanoencapsulated phase‐change materials (nePCMs) are investigated for enhancing thermal energy storage. However, the shell of these nanocapsules may fail due to stress developed during thermal processes, leading to melting enthalpy loss. To overcome this problem, SiO2 and Al2O3 coatings on Sn nanoparticles are synthesized by atomic layer deposition (ALD). To study the influence of shell thickness and composition on the probability of failure (POF) of nePCM shells in single‐ and multicoated nePCMs, a probabilistic numerical tool combining Monte Carlo techniques and a thermomechanical finite‐element model with phase change are used. The uncertainties of the material and geometrical properties of nePCMs are included in the analysis. Both deterministic and probabilistic failure criteria are taken into account to consider the effect of dispersion on tensile strength. The results indicate that multicoated nePCMs enhance thermomechanical performance in relation to their single‐coated counterparts. Both the numerical simulations and experiments confirm that the POF of nePCM shells and melting enthalpy loss in multicoated nePCMs lower with shell thickness. The results after 50 ALD cycles indicate that Al2O3 coatings exhibit better performance because a POF of 1.66% is obtained with 1.1% enthalpy loss, while the POF for SiO2 is 72.38% with 3.5% enthalpy loss.

Coupled nonlinear mechanics for the electromechanical response of multi-stable piezoelectric shallow shells with piezoelectric films

This paper considers the nonlinear electromechanical response of shallow piezoelectric laminated shells of arbitrary double curvature, undergoing to snap through buckling and eventually to elastic instability, under mechanical pressure loads. The computational framework is based on coupled nonlinear mechanics encompassing the electromechanical coupling field and geometric nonlinearity due to large displacements and rotations. The first shear deformation theory is combined with a linear layerwise theory for describing the elastic and electric state variables through the laminate thickness, respectively. The governing equations are expressed with respect to an orthogonal curvilinear coordinate system. Building upon the nonlinear multifield mechanics an eight-node shell finite element is developed to discretize the generalized coupled nonlinear equations, which are subsequently linearized and iteratively solved, using the Cylindrical Arc-Length method in combination with the Newton-Raphson iterative technique. Numerical results demonstrate the capability of the present model to predict the complex electromechanical response of shallow cylindrical shells that transit between two stable equilibrium states. The electromechanical (generated electric charge-energy) conversion is highly complex (depending on both nonlinear piezoelectric and stiffness matrices) and predicted along the stable and unstable paths of bi-stability. At the same time the feasibility to relate the sensory electric potential with the snap through buckling of smart shells is also quantified. The influence of shell thickness, curvature and laminate configuration on the electromechanical conversion, is finally investigated.

Effect of shell diameter and shell thickness on coconut-shell-halving force

Design of any product is primarily based on the characteristics of various parameters that will be having direct influence on their functionality. The aim of this study is to understand the influence of physical parameters of coconuts, viz. shell diameter and shell thickness on the shell halving force, so that proper designing and development of an efficient energy efficient shell-splitting tool can be done. In line with this objective, experimental investigations have been carried out on 50 green and 50 dry fully matured coconuts to measure force needed in compression for rupturing the shell equatorially. The experimentations have been carried out using a Universal Testing Machine. Results suggest a negative correlation between shell diameter and shell halving force. However, influence of shell thickness on shell halving force has been found to be less significant. Combined analysis of the results suggests that coconuts having large shell diameter and small thickness require lower shell halving force.

Influence of shell thickness on the refractive index sensitivity of localized surface plasmon resonance inflection points in silver-coated gold nanorods.

Silver-coated gold nanorods (Ag@AuNRs) have great potential for biological and chemical sensing, because of their sensitive spectral response to the local environment and unique localized surface plasmon resonance (LSPR) properties. Herein, we investigated the sensitivities of single Ag@AuNRs with different shell thickness with respect to variations in the refractive index (RI) of the surrounding environment. Single Ag@AuNRs with thick shell thickness showed higher RI sensitivity than single Ag@AuNRs with thin shell thickness, which demonstrates the improvement of LSPR sensor due to increase in silver layer thickness. Furthermore, we investigated homogeneous LSPR scattering inflection points (IFs) to better understand the RI sensitivity of single Ag@AuNRs with different Ag shell thickness. The LSPR IFs showed higher RI sensitivity when compared with the frequency shifts of counterpart LSPR peaks observed for single Ag@AuNRs. Finally, single Ag@AuNRs with thick Ag shell demonstrated improved RI sensitivity when compared with single AuNRs with thin Ag shell in the homogeneous LSPR IFs.

Electron Localization and Transport in SnO2/TiO2 Mesoporous Thin Films: Evidence for a SnO2/SnxTi1-xO2/TiO2 Structure.

A study of SnO2/TiO2 core/shell films was undertaken to investigate the influences of shell thickness and post deposition sintering on electron localization and transport properties. Electrochemical reduction of the materials resulted in the appearance of a broad visible-near IR absorbance that provided insights into the electronic state(s) within the core/shell structures. As the shell thickness was increased from 0.5 to 5 nm, evidence for the presence of a SnxTi1-xO2 interfacial state emerged that was physically located between the core and the shell. The lifetime of photoinjected electrons increased with the shell thickness. Electron transport occurred through the SnO2 core; however, when materials with shell thicknesses ≥2 nm were annealed at 450 °C, a new electron transport pathway through the shell was evident. The data indicate that these materials are best described as SnO2/SnxTi1-xO2/TiO2 where electrons preferentially localize in a SnxTi1-xO2 interfacial state and transport through SnO2 and annealed TiO2 (if present). The implications of these results for applications in solar energy conversion are discussed.

Biodegradable biopolymer network structures to create delayed burst digestive release of encapsulated lipids

This study sought to investigate whether encapsulation of lipids in core-shell hydrogel structures of tailored shell porosity could create a delayed burst release of encapsulated lipids, and examined the underpinning mechanisms. We demonstrated that gastrointestinal digestion of core-shell structures resulted in a delay in the onset of lipid digestion, without affecting lipid digestion kinetics. Systematic increase in hydrogel protein content above 65 g/L lead to an exponential increase in digestive delay (250 min). Whilst an increase in xanthan content between 5 and 9 g/L lead to a modest decrease in digestive delay (40 min). Rheological investigations revealed a linear relationship between hydrogel storage modulus G′ and digestive breakdown delay (T1/2). Given that G’ is directly related to hydrogel mesh size, this result suggests that the main factor controlling the timing of digestive release is the average mesh size of the outer protein hydrogel. A kinetic model was created to describe the delayed burst release behaviour of encapsulated lipids and successfully predicted the influence of shell thickness, shell protein density on the timing of gastro-intestinal release (in vitro). By combining microstructural/rheological experiments with in vitro digestive studies we have understood the main factors controlling the digestive breakdown of hierarchical biopolymer hydrogels. We could successfully miniaturise these core-shell structures so they would easily empty from the stomach whilst maintaining programmable delayed burst release. We have created a novel family of core-shell hydrogel oral dosage forms for the delivery of poorly soluble drugs and the programmed delivery of lipids within the gut.

Hierarchically structured phase separated biopolymer hydrogels create tailorable delayed burst release during gastrointestinal digestion

The on demand delivery of novel peptide actives, traditional pharmaceuticals, nutrients and/or vitamins is a ever present challenge due to the digestive and metabolic degradation of the active and the delivery vehicle. Biodegradable biopolymer hydrogels have long held promise as candidates for creating tailored release profiles due to the ability to control gel porosity. The present study describes the creation of novel hierarchical biopolymer hydrogels for the controlled release of lipids/lipophilic actives pharmaceutical ingredients (APIs), and mathematically describes the mechanisms that affect the timing of release. The creation of phase separated protein/polysaccharide core (6.6 wt% gelatin, 40 wt% Oil in water emulsion) shell structures (7 g/L xanthan with 70–140 g/L β-lactoglobulin) altered enzyme mass transport processes. This core shell structure enabled the creation of a tailorable burst release of API during gastrointestinal digestion where there is a delay in the onset of release, without affecting the kinetics of release. The timing of the delay could be readily programmed (with release of between 60 and 240 min) by controlling either the thickness or protein concentration (between 70 g/L and 140 g/L β-lactoglobulin) of the outer mixed biopolymer hydrogel shell (7 g/L xanthan with 70–140 g/L β-lactoglobulin). Enzyme diffusion measurements demonstrated that surface erosion was the main degradation mechanism. A kinetic model was created to describe the delayed burst release behaviour of APIs encapsulated within the core, and successfully predicted the influence of shell thickness and shell protein density on the timing of gastro-intestinal release (in vitro). Our work highlights the creation of a novel family of core-shell hydrogel oral dosage forms capable of programmable delivery of lipids/lipophilic APIs. These findings could have considerable implications for the delivery of peptides, poorly soluble drugs, or the programmed delivery of lipids within the gastrointestinal tract.

Influence of Shell Thickness on the Colloidal Stability of Magnetic Core-Shell Particle Suspensions.

We present a Discrete Element study of the behavior of magnetic core-shell particles in which the properties of the core and the shell are explicitly defined. Particle cores were considered to be made of pure iron and thus possessed ferromagnetic properties, while particle shells were considered to be made of silica. Core sizes ranged between 0.5 and 4.0 μm with the actual particle size of the core-shell particles in the range between 0.6 and 21 μm. The magnetic cores were considered to have a magnetization of one tenth of the saturation magnetization of iron. This study aimed to understand how the thickness of the shell hinders the formation of particle chains. Chain formation was studied with different shell thicknesses and particle sizes in the presence and absence of an electrical double layer force in order to investigate the effect of surface charge density on the magnetic core-shell particle interactions. For core sizes of 0.5 and 4.0 μm the relative shell thicknesses needed to hinder the aggregation process were approximately 0.4 and 0.6 respectively, indicating that larger core sizes are detrimental to be used in applications in which no flocculation is needed. In addition, the presence of an electrical double layer, for values of surface charge density of less than 20 mC/m2, could stop the contact between particles without hindering their vertical alignment. Only when the shell thickness was considerably larger, was the electrical double layer able to contribute to the full disruption of the magnetic flocculation process.