A Review on the Current State of Microcapsule-Based Self-Healing Dental Composites

Resin-based dental composites, commonly used in dentistry, offer several advantages including minimally invasive application, esthetically pleasing appearance, and good physical and mechanical properties. However, these dental composites can be susceptible to microcracks due to various factors in the complex oral environment. These microcracks can potentially lead to clinical restoration failure. Conventional materials and methods are inadequate for detecting and repairing these microcracks in situ. Consequently, incorporating self-healing properties into dental composites has become a necessity. Recent years have witnessed rapid advancements in self-healing polymer materials, drawing inspiration from biological bionics. Microcapsule-based self-healing dental composites (SHDCs) represent some of the most prevalent types of self-healing materials utilized in this domain. In this article, we undertake a comprehensive review of the most recent literature, highlighting key insights and findings related to microcapsule-based SHDCs. Our discussion centers particularly on the preparation techniques, application methods, and the promising future of self-healing microcapsules in the field of dentistry.

Phase Change Composite Microcapsules with Low-Dimensional Thermally Conductive Nanofillers: Preparation, Performance, and Applications

Phase change materials (PCMs) have been extensively utilized in latent thermal energy storage (TES) and thermal management systems to bridge the gap between thermal energy supply and demand in time and space, which have received unprecedented attention in the past few years. To effectively address the undesirable inherent defects of pristine PCMs such as leakage, low thermal conductivity, supercooling, and corrosion, enormous efforts have been dedicated to developing various advanced microencapsulated PCMs (MEPCMs). In particular, the low-dimensional thermally conductive nanofillers with tailorable properties promise numerous opportunities for the preparation of high-performance MEPCMs. In this review, recent advances in this field are systematically summarized to deliver the readers a comprehensive understanding of the significant influence of low-dimensional nanofillers on the properties of various MEPCMs and thus provide meaningful enlightenment for the rational design and multifunction of advanced MEPCMs. The composition and preparation strategies of MEPCMs as well as their thermal management applications are also discussed. Finally, the future perspectives and challenges of low-dimensional thermally conductive nanofillers for constructing high performance MEPCMs are outlined.

Superhydrophilic Modified Elastomeric RGO Aerogel Based Hydrated Salt Phase Change Materials for Effective Solar Thermal Conversion and Storage

As a typical phase-change material (PCM) with high heat storage capacity and wide distribution, hydrated salts play broad and critical roles in solar energy utilization in recent years. However, the leakage and supercooling problems of hydrated salts have been a constraint to their further practical applications. In the current work, the super-hydrophilic reduced graphene oxide (RGO) aerogels modified by konjac glucomannan (KGM) as supporting structural materials are prepared by the hydrothermal reaction-freeze-drying, which can effectively absorb and convert visible sunlight energy into thermal energy. In addition, the super-hydrophilic aerogels compounded with PCMs can ameliorate the shortcoming of leakage and suppress the supercooling temperature as low about 0.2-1.5 °C in the freezing process. Under 1 sun irradiation, the prepared sodium acetate trihydrate/KGM-modified graphene oxide aerogel (SAT/KRGO) composite PCM achieves a high photothermal conversion efficiency (86.3%) due to its good light absorption property. The number of cycles has no apparent effect on the supercooling of the composite materials, suggesting their stable thermal cycles and thermal storage.

Recyclable low-temperature phase change microcapsules for cold storage

Recyclable low-temperature phase change microcapsules (LTPCMs) have the potential applications in the short-distance cold chain transportation due to their reliable reusability in cold storage. Herein, LTPCMs are synthesized via in-situ suspension copolymerization of styrene and methyl methacrylate in absence of harm substances, providing the non-crosslinking copolymer shells. n-Dodecane, n-tridecane and n-tetradecane, inducing the microphase separation of non-crosslinking copolymers, are successfully encapsulated to achieve n-do-LTPCMs, n-tri-LTPCMs and n-tetra-LTPCMs, which respectively bear the high phase change enthalpy of 110.53 J·g^-1 at -8.69 °C, 38.33 J·g^-1/93.71 J·g^-1 at -17.61 °C/-4.96 °C and 166.79 J·g^-1 at 8.59 °C and subsequently show the cold-discharging periods of 30 min, 40 min and 120 min. The multiple circulation of cold-discharging process indicates the excellent recyclability for cold storage owing to their unchanged cold-discharging period. Especially, n-tetra-LTPCM-65 bears the best comprehensive cold-storing performance in all the previously reported LTPCMs, such as narrow cold-discharging temperature range of 3-4 °C, long cold-discharging period of 69-120 min and low cold-discharging capacity of 33.4 J·g^-1·K^-1. This work successfully provided the recyclable LTPCMs for cold storage in the short-distance cold chain transportation.

Phase Change Material (PCM) Microcapsules for Thermal Energy Storage

Phase change materials (PCMs) are gaining increasing attention and becoming popular in the thermal energy storage field. Microcapsules enhance thermal and mechanical performance of PCMs used in thermal energy storage by increasing the heat transfer area and preventing the leakage of melting materials. Nowadays, a large number of studies about PCM microcapsules have been published to elaborate their benefits in energy systems. In this paper, a comprehensive review has been carried out on PCM microcapsules for thermal energy storage. Five aspects have been discussed in this review: classification of PCMs, encapsulation shell materials, microencapsulation techniques, PCM microcapsules’ characterizations, and thermal applications. This review aims to help the researchers from various fields better understand PCM microcapsules and provide critical guidance for utilizing this technology for future thermal energy storage.

Controlling the Release from Enzyme-Responsive Microcapsules with a Smart Natural Shell

We design a natural and simple core-shell-structured microcapsule, which releases its cargo only when exposed to lipase. The cargo is entrapped inside a gel matrix, which is surrounded by a double-layer shell containing an inner solid lipid layer and an outer polymer layer. This outer polymer layer can be designed according to the intended biological system and is responsible for protecting the microcapsule architecture and transporting the cargo to the desired site of action. The lipid layer contains natural ester bonds, which are digested by lipase, controlling the release of cargo from the microcapsule core. To demonstrate the feasibility of this approach, our model system includes a colorant bixin entrapped inside a κ-carrageenan gel matrix. This core is surrounded by an inner beeswax-palmitic acid layer and an outer casein-poloxamer 338 layer. These fabricated microcapsules are then applied into Cheddar cheese, where they selectively color the cheese matrix.

Preparation and characterization of sodium thiosulfate pentahydrate/silica microencapsulated phase change material for thermal energy storage

Microencapsulated phase change materials (MicroPCM) were successfully fabricated by encapsulation of sodium thiosulfate pentahydrate (SoTP) as core with silica shell using sol–gel method.