A facile microencapsulation of phase change materials within silicone-based shells by using glass capillary devices

Phase Change Materials Meet Microfluidic Encapsulation

Improving the utilization of thermal energy is crucial in the world nowadays due to the high levels of energy consumption. One way to achieve this is to use phase change materials (PCMs) as thermal energy storage media, which can be used to regulate temperature or provide heating/cooling in various applications. However, PCMs have limitations like low thermal conductivity, leakage, and corrosion. To overcome these challenges, PCMs are encapsulated into microencapsulated phase change materials (MEPCMs) capsules/fibers. This encapsulation prevents PCMs from leakage and corrosion issues, and the microcapsules/fibers act as conduits for heat transfer, enabling efficient exchange between the PCM and its surroundings. Microfluidics-based MEPCMs have attracted intensive attention over the past decade due to the exquisite control over flow conditions and size of microcapsules. This review paper aims to provide an overview of the state-of-art progress in microfluidics-based encapsulation of PCMs. The principle and method of preparing MEPCM capsules/fibers using microfluidic technology are elaborated, followed by the analysis of their thermal and microstructure characteristics. Meanwhile, the applications of MEPCM in the fields of building energy conservation, textiles, military aviation, solar energy utilization, and bioengineering are summarized. Finally, the perspectives on MEPCM capsules/fibers are discussed.

Near-superhydrophobic silicone microcapsule arrays encapsulating ionic liquid electrolytes for micro-power storage assuming use in seawater

Micro-energy storage, which is convenient for combination with energy harvesting, is known to be realized by microencapsulation with various shell materials, its application is limited to land. Here, we succeeded in fabricating a silicone microcapsule array encapsulating an ionic liquid electrolyte that can store minute power in NaCl solution as well as a minute power generation method. The ArF excimer laser-irradiated silicone rubber underneath silica microspheres was photochemically and periodically swelled by the photodissociation of silicone. Accompanied by the microswellings, the lower molecular weight silicones generated were ejected along a curvature of each the microsphere to enclose the microspheres. After the chemical etching, the silicone microcapsule arrays became hollow. Moreover, each the hollow silicone microcapsule could entrap an ionic liquid in a vacuum. In addition, the silicone microcapsules before and after the encapsulating ionic liquid showed a superhydrophobic or near-superhydrophobic property. As a result, the silicone microcapsule arrays could be confined in a uniform air gap of electrically insulated region in NaCl solution. This means that each the silicone microcapsule encapsulating ionic liquid as electrolytes enables to function as an electric double layer capacitor for micro-power storage, aiming to connect with Internet of Things devices that work under seawater.

Temperature-humidity dual regulation of a single-core-double-shell microcapsule fabricated by electrostatic-assembly and chemical precipitation

Humidity and temperature control materials have attracted increasing attention due to their energy saving and intelligent regulation of human comfort in the field of interior building and clothing. Phase change microcapsules have been widely used, however, most of which focus on temperature regulation without humidity control. In this work, we report a novel temperature-humidity dual regulation microcapsule with single-core-double-shell structure. FT-IR and XRD measurements confirmed that the shell materials were successfully fabricated on the paraffin core via electrostatic-assembly and the subsequent chemical precipitation method. SEM, TEM and optical microscope photos showed that the microcapsules were spherical morphology with layer-by-layer shells at a diameter around 2-5 μm. The SiO2 shell was aggregated from nano-sized particles and formed a loose and porous micro-structure, supported by the result of N2 adsorption-desorption isotherms. In addition, the synergistic effect of hydrophilic and porous loose (chitosan/GO/chitosan)-SiO2 double shells endowed the microcapsules with humidity regulation. The constructed microcapsules showed temperature regulation behavior due to its phase change performance of paraffin and good thermal durability after 10 thermal cycles. They also showed stable humidity regulation performance after repeated adsorption/desorption. The simulation experiments of temperature and humidity regulation indicated that the microcapsule could keep the temperature and humidity in a stable range. The as-prepared microcapsules have outstanding temperature and humidity regulation properties, showing an application prospects in energy-saving fields.

A Novel Prototype Device for Microencapsulation of Benznidazole: In Vitro/In Vivo Studies

This study was aimed to design a simple and novel prototype device for the production of polymeric microparticles. To prove the effectiveness of this device, benznidazole microparticles using chitosan as carrier and NaOH, KOH, or SLS as counter ions were used. For comparison, benznidazole microparticles were prepared by the conventional dripping technique (syringe and gauge) using the same excipients. Microparticles were characterized in terms of encapsulation efficiency, particle shape, size and surface topography, crystallinity characteristics, thermal behavior, and dissolution rate. Then, the pharmacokinetic parameters were evaluated after the oral administration of the microparticles to healthy Wistar rats. The prepared formulations, by means of this device, showed good drug encapsulation efficiency (> 70%). Release studies revealed an increased dissolution of benznidazole from chitosan microparticles prepared using the novel device. It achieved more than 90% in 60 min, while those of the conventional microparticles and raw drug achieved 65% and 68%, respectively, during the same period. Almost spherical benznidazole microparticles with a smooth surface and size around 10-30 μm were observed using scanning electron microscopy. Thermal analysis and X-ray diffraction studies suggested a partial reduction of drug crystallinity. Moreover, the relative oral bioavailability of the novel benznidazole microparticles showed that the area under the curve for the microencapsulated drug was 10.3 times higher than the raw drug. Thus, these findings indicate that the designed glass prototype device is a useful alternative to formulate benznidazole polymeric microparticles with improved biopharmaceutical properties and could be useful for other therapeutic microparticulate systems.