Low‐loss nanostructured dielectric metasurfaces have emerged as a breakthrough platform for ultrathin optics and cutting‐edge photonic applications, including beam shaping, focusing, and holography. ...However, the static nature of their constituent materials has traditionally limited them to fixed functionalities. Tunable all‐dielectric infrared Huygens' metasurfaces consisting of multi‐layer Ge disk meta‐units with strategically incorporated non‐volatile phase change material Ge3Sb2Te6 are introduced. Switching the phase‐change material between its amorphous and crystalline structural state enables nearly full dynamic light phase control with high transmittance in the mid‐IR spectrum. The metasurface is realized experimentally, showing post‐fabrication tuning of the light phase within a range of 81% of the full 2π phase shift. Additionally, the versatility of the tunable Huygen's metasurfaces is demonstrated by optically programming the spatial light phase distribution of the metasurface with single meta‐unit precision and retrieving high‐resolution phase‐encoded images using hyperspectral measurements. The programmable metasurface concept overcomes the static limitations of previous dielectric metasurfaces, paving the way for “universal” metasurfaces and highly efficient, ultracompact active optical elements like tunable lenses, dynamic holograms, and spatial light modulators.
Tunable all‐dielectric Huygens' metasurfaces consisting of hybrid germanium and phase change material Ge3Sb2Te6 disk meta‐units are introduced. Switching the Ge3Sb2Te6 between its structural phase states enables dynamic light phase control with high transmittance. The versatility of these metasurfaces is demonstrated by optically programming the spatial light phase distribution of the metasurface with single meta‐unit precision and retrieving high‐resolution phase‐encoded images.
In modern heat transfer systems, thermal storage not only causes the balance between demand and supply, but also improves the heat transfer efficiency in these systems. In the present study, a ...comprehensive review of the applications of micro- or nano-encapsulated phase change slurries (MPCMs/NPCMs), as well as their effects on thermal storage and heat transfer enhancement, has been conducted. MPCMs/NPCMs have a myriad of applications and various usages such as pipe and channel flows, photovoltaic/thermal, solar heaters, air conditioning systems, storage tanks and heat pipes that have been categorized and studied. It was found that there are many advantageous adding MPCM/NPCM to the base fluid. The most important effect is that the addition of PCMs to the base fluid can intensify the capacity of energy absorption in the base fluid. These materials can absorb a high proportion of received energy by changing their phase and prevent temperature increment of the base fluid. Thereupon, the specific heat of the fluid in the presence of the micro-/nano-capsules increases. Moreover, in most studies reviewed, heat transfer coefficient and Nusselt number increase by the addition of micro-/nano-capsules to the base fluid. Also, the addition of MPCM/NPCM to the base fluid could make this material pumpable, although increment in the concentration of micro-/nano-capsules raises the viscosity of the working fluid and thereupon the pumping power. On the other hand, for a same heat load, the pumping power decreases due to the lower required flow rate in comparison with pure working fluid. The most important factor that must be considered in the application of MPCMs/NPCMs is the complete phase change of the material. Given the favorable thermal and fluid characteristics of MPCMs/NPCMs, the utilization of these materials could be a promising method to transfer heat and store it with high efficiency and low pumping power.
Six lignin‐based polyols (LBPs) have been prepared by cationic ring opening polymerization of an oxirane in the presence of an organosolv lignin in tetrahydrofuran (THF) as reaction media and ...co‐monomer. The prepared LBPs have been characterized and tested for the first time as phase change materials (PCMs) for thermal energy storage (TES) at low temperature. It was found a strong influence of the LBPs composition on their performance to storage thermal energy. Thus, LBPs with higher THF wt% content and lower oxirane/THF mass ratio exhibit the highest latent heats. Furthermore, a clear inversely proportional trend between the oxirane/THF mass ratio and the melting temperatures of the prepared LBPs was noticed. Among the prepared LBPs, the highest obtained latent heat was 53.7 J/g demonstrating the potential application of lignin as feedstock for PCMs preparation. To the best of our knowledge, this is the first time that a biomass derived PCM based on lignin has been studied and considered for TES applications at low temperature. LBPs show energetic solid–liquid transitions that point out their promising potential as bio‐PCMs. This work paves the way to introduce new bio‐based PCMs from lignin in TES systems, for example, in a more sustainable construction sector.
Lignin has been upgraded to thermal energy storage material (LBP) and the highest obtained latent heat was 53.7 J/g demonstrating the potential application of lignin as feedstock for PCMs preparation. To the best of our knowledge, this is the first time that a biomass derived PCM based on lignin has been studied and considered for TES applications at low temperature. This work paves the way to introduce new bio‐based PCMs from lignin in TES systems.
The development of flat, compact beam‐steering devices with no bulky moving parts is opening up a new route to a variety of exciting applications, such as LIDAR scanning systems for autonomous ...vehicles, robotics and sensing, free‐space, and even surface wave optical signal coupling. In this paper, the design, fabrication and characterization of innovative, nonvolatile, and reconfigurable beam‐steering metadevices enabled by a combination of optical metasurfaces and chalcogenide phase‐change materials is reported. The metadevices reflect an incident optical beam in a mirror‐like fashion when the phase‐change layer is in the crystalline state, but reflect anomalously at predesigned angles when the phase‐change layer is switched into its amorphous state. Experimental angle‐resolved spectrometry measurements verify that fabricated devices perform as designed, with high efficiencies, up to 40%, when operating at 1550 nm. Laser‐induced crystallization and reamorphization experiments confirm reversible switching of the device. It is believed that reconfigurable phase‐change‐based beam‐steering and beam‐shaping metadevices, such as those reported here, can offer real applications advantages, such as high efficiency, compactness, fast switching times and, due to the nonvolatile nature of chalcogenide phase‐change materials, low power consumption.
Beam‐steering devices with no moving parts are likely to find widespread applications in areas such as LIDAR scanning systems for autonomous vehicles, robotics and sensing, telecommunications, and optical signal coupling. Here, the design, fabrication and characterization of innovative, fast, nonvolatile, and reconfigurable beam‐steering devices enabled by a combination of optical metasurfaces and chalcogenide phase‐change materials is reported.
In recent years the use of thermal energy storage with phase change materials has become a topic with a lot of interest within the research community, but also within architects and engineers. Many ...publications have appeared, and several books, but the information is disseminated and not very much organised. This paper shows a review of the latest publications on the use of phase change materials (PCM) in buildings. The paper compiles information about the requirements of the use of this technology, classification of materials, materials available and problems and possible solutions on the application of such materials in buildings.
Inspired by the great success of fiber optics in ultrafast data transmission, photonic computing is being extensively studied as an alternative to replace or hybridize electronic computers, which are ...reaching speed and bandwidth limitations. Mimicking and implementing basic computing elements on photonic devices is a first and essential step toward all‐optical computers. Here, an optical pulse‐width modulation (PWM) switching of phase‐change materials on an integrated waveguide is developed, which allows practical implementation of photonic memories and logic devices. It is established that PWM with low peak power is very effective for recrystallization of phase‐change materials, in terms of both energy efficiency and process control. Using this understanding, multilevel photonic memories with complete random accessibility are then implemented. Finally, programmable optical logic devices are demonstrated conceptually and experimentally, with logic “OR” and “NAND” achieved on just a single integrated photonic phase‐change cell. This study provides a practical and elegant technique to optically program photonic phase‐change devices for computing applications.
An optical pulse‐width modulation (PWM) method for switching of phase‐change materials can bring both energy and speed efficiency gains, which enables direct accessibility of any level of photonic phase‐change memories. The PWM scheme naturally lends itself to the realization of nonvolatile programmable on‐chip photonic logic functions of “OR” and “NAND” on a single photonic memory cell.
•The synthesis methods of microencapsulated phase change materials were summarized.•The characterization of microencapsulated phase change materials were presented.•Thermal properties and reliability ...of microencapsulated phase change materials were discussed.•Applications of microencapsulated phase change materials were analyzed.
In recent years microencapsulation of phase change materials has become popular in thermal energy storage field. Commercially produced microencapsulated phase change material (MPCM) is also available in market today. Microencapsulation enhances thermal and mechanical properties of phase change materials used in thermal energy storage. Microencapsulation can be achieved through different techniques and using different shell materials. As the microencapsulation of PCM is gaining increased attention, more and more research works on MPCM are getting published. This review attempts to summarize the available research information on synthesis, characterization, properties and applications of microencapsulated phase change materials for thermal energy storage. The synthesis methods of microencapsulated phase change materials, such as physical synthesis methods like spray drying, physical chemical synthesis methods like complex coacervation and sol–gel process, and chemical synthesis methods like suspension polymerization, emulsion polymerization, interfacial polymerization, in-situ polymerization and condensation polymerization, are presented. The properties of microencapsulated phase change materials like physical properties, chemical properties and thermal properties are analyzed. The applications of microencapsulated phase change materials in buildings, textiles, MPCM slurry and composite foams are also expounded.
A smart release system responsive to near‐infrared (NIR) light is developed for intracellular drug delivery. The concept is demonstrated by coencapsulating doxorubicin (DOX) (an anticancer drug) and ...IR780 iodide (IR780) (an NIR‐absorbing dye) into nanoparticles made of a eutectic mixture of naturally occurring fatty acids. The eutectic mixture has a well‐defined melting point at 39 °C, and can be used as a biocompatible phase‐change material for NIR‐triggered drug release. The resultant nanoparticles exhibit prominent photothermal effect and quick drug release in response to NIR irradiation. Fluorescence microscopy analysis indicates that the DOX trapped in the nanoparticles can be efficiently released into the cytosol under NIR irradiation, resulting in enhanced anticancer activity. A new platform is thus offered for designing effective intracellular drug‐release systems, holding great promise for future cancer therapy.
A smart system responsive to near‐infrared (NIR) light is developed by coencapsulating a drug and an NIR‐absorbing dye into nanoparticles made of a eutectic mixture of naturally occurring fatty acids. Photothermal heating under NIR irradiation facilitates rapid and efficient intracellular drug release, leading to enhancement in anticancer activity.
Preventing water droplets from transitioning to ice is advantageous for numerous applications. It is demonstrated that the use of certain phase‐change materials, which are in liquid state under ...ambient conditions and have melting point higher than the freezing point of water, referred herein as phase‐switching liquids (PSLs), can impede condensation–frosting lasting up to 300 and 15 times longer in bulk and surface infused state, respectively, compared to conventional surfaces under identical environmental conditions. The freezing delay is primarily a consequence of the release of trapped latent heat due to condensation, but is also affected by the solidified PSL surface morphology and its miscibility in water. Regardless of surface chemistry, PSL‐infused textured surfaces exhibit low droplet adhesion when operated below the corresponding melting point of the solidified PSLs, engendering ice and frost repellency even on hydrophilic substrates. Additionally, solidified PSL surfaces display varying degrees of optical transparency, can repel a variety of liquids, and self‐heal upon physical damage.
Certain phase‐change materials can significantly delay icing and frosting in bulk form or, being infused into hydrophilic textured substrates, exhibit varying degrees of optical transparency, can repel a myriad of liquids thereby preventing staining, are capable of self‐repairing by being resilient toward mechanical damage during condensation, and thus can have far‐reaching technological impact.
The present paper is the first comprehensive review of the integration of phase change materials in building walls. Many considerations are discussed in this paper including physical considerations ...about building envelope and phase change material, phase change material integration and thermophysical property measurements and various experimental and numerical studies concerning the integration. Even if the integrated phase change material have a good potential for reducing energy demand, further investigations are needed to really assess their use.
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