Wearable Aerogels for Personal Thermal Management and Smart Devices

Extreme climates have become frequent nowadays, causing increased heat stress in human daily life. Personal thermal management (PTM), a technology that controls the human body's microenvironment, has become a promising strategy to address heat stress. While effective in ordinary environments, traditional high-performance fibers, such as ultrafine, porous, highly thermally conductive, and phase change materials, fall short when dealing with harsh conditions or large temperature fluctuations. Aerogels, a third-generation superinsulation material, have garnered extensive attention among researchers for their thermal management applications in building energy conservation, transportation, and aerospace, attributed to their extremely low densities and thermal conductivity. While aerogels have historically faced challenges related to weak mechanical strength and limited secondary processing capacity, recent advancements have witnessed notable progress in the development of wearable aerogels for PTM. This progress underscores their potential applications within extremely harsh environments, serving as self-powered smart devices and sensors. This Review offers a timely overview of wearable aerogels and their PTM applications with a particular focus on their wearability and suitability. Finally, the discussion classifies five types of PTM applications based on aerogel function: thermal insulation, heating, cooling, adaptive regulation (involving thermal insulation, heating, and cooling), and utilization of aerogels as wearable smart devices.

Thermochromic Nanocellulose Films for Temperature-Adaptive Passive Cooling

Energy efficiency in habitation spaces is a pivotal topic for maintaining energy sufficiency, cutting climate impact, and facilitating economic savings; thus, there is a critical need for solutions aimed at tackling this problem. One viable approach involves complementing active cooling methods with powerless or passive cooling ones. Moreover, considerable scope remains for the development of passive radiative cooling solutions based on sustainable materials. Cellulose, characterized by its abundance, renewability, and biodegradability, emerges as a promising material for this purpose due to its notable radiative cooling potential exploiting the mid-infrared (MIR) atmospheric transmission window (8-13 μm). In this work, we propose the utilization of thermochromic (TC) materials in conjunction with cellulose nanofibrils (CNF) to confer temperature-dependent adaptivity to hybrid CNF films. We employ a concept where high reflection, coupled with MIR emission in the heated state, facilitates cooling, while high visible light absorption in the cold state allows heating, thus enabling adaptive thermal regulation. CNF films were doped with black-to-leuco TC particles, and a thin silver layer was optionally applied to the films. The films exhibited a rapid transition (within 1 s) in their optical properties at ∼22 °C, becoming transparent above the transition temperature. Visible range transmittance of all samples ranged from 60 to 90%, with pronounced absorption in the 8-13 μm range. The cooling potential of the films was measured at 1-4 °C without any Ag layer and ∼10 °C with a Ag layer. In outdoor field testing, a peak cooling value of 12 °C was achieved during bright sunshine, which is comparable to a commercial solar film. A simulation model was also built based on the experimental results. The concept presented in this study extends beyond applications as standalone films but has applicability also in glass coatings. Overall, this work opens the door for a novel application opportunity for green cellulose-based materials.

Facile Access to High Solid Content Monodispersed Microspheres via Dual-Component Surfactants Regulation toward High-Performance Colloidal Photonic Crystals

Monodispersed microspheres play a major role in optical science and engineering, providing ideal building blocks for structural color materials. However, the method toward high solid content (HSC) monodispersed microspheres has remained a key hurdle. Herein, a facile access to harvest monodispersed microspheres based on the emulsion polymerization mechanism is demonstrated, where anionic and nonionic surfactants are employed to achieve the electrostatic and steric dual-stabilization balance in a synergistic manner. Monodispersed poly(styrene-butyl acrylate-methacrylic acid) colloidal latex with 55 wt% HSC is achieved, which shows an enhanced self-assembly efficiency of 280% compared with the low solid content (10 wt%) latex. In addition, Ag-coated colloidal photonic crystal (Ag@CPC) coating with near-zero refractive index is achieved, presenting the characteristics of metamaterials. And an 11-fold photoluminescence emission enhancement of CdSe@ZnS quantum dots is realized by the Ag@CPC metamaterial coating. Taking advantage of high assembly efficiency, easily large-scale film-forming of the 55 wt% HSC microspheres latex, robust Ag@CPC metamaterial coatings could be easily produced for passive cooling. The coating demonstrates excellent thermal insulation performance with theoretical cooling power of 30.4 W m-2, providing practical significance for scalable CPC architecture coatings in passive cooling.

Self-sustained and Insulated Radiative/Evaporative Cooler for Daytime Subambient Passive Cooling

Passive cooling technologies are one of the promising solutions to the global energy crisis due to no consumption of fossil fuels during operation. However, the existing radiative and evaporative coolers still have problems achieving daytime subambient cooling while maintaining evaporation over the long term. Here, we propose a self-sustained and insulated radiative/evaporative cooler (SIREC), which consists of a porous polyethylene film (P-PE) at the top, an air layer in the middle, and poly(vinyl alcohol) hydrogel with lithium bromide (PLH) at the bottom. In particular, the P-PE shows high solar reflectance (R̅solar = 0.91) and long-wave infrared transmittance (τ̅LWIR = 0.92), which reflects sunlight while enhancing the direct radiative heat transfer between outer space and PLH (ε̅LWIR = 0.96) for sky radiative cooling. In addition, the desirable vapor permeability (579 s m-1) of the P-PE also results in good compatibility with PLH for evaporative cooling (EC). Moreover, the PLH's ability to harvest atmospheric water at night provides self-sustainment for daytime EC. The air layer between P-PE and PLH further enhances the subambient cooling performance of the SIREC. These findings indicate promising prospects for the integration of passive cooling technologies.

Ultrahigh Passive Cooling Power in Hydrogel with Rationally Designed Optofluidic Properties

The cooling power of a radiative cooler is more than halved in the tropics, e.g., Singapore, because of its harsh weather conditions including high humidity (84% on average), strong downward atmospheric radiation (∼40% higher than elsewhere), abundant rainfall, and intense solar radiation (up to 1200 W/m2 with ∼58% higher UV irradiation). So far, there has been no report of daytime radiative cooling that well achieves effective subambient cooling. Herein, through integrated passive cooling strategies in a hydrogel with desirable optofluidic properties, we demonstrate stable subambient (4-8 °C) cooling even under the strongest solar radiation in Singapore. The integrated passive cooler achieves an ultrahigh cooling power of ∼350 W/m2, 6-10 times higher than a radiative cooler in a tropical climate. An in situ study of radiative cooling with various hydration levels and ambient humidity is conducted to understand the interaction between radiation and evaporative cooling. This work provides insights for the design of an integrated cooler for various climates.

From Chitosan to Chitin: Bio-Inspired Thin Films for Passive Daytime Radiative Cooling

Passive radiative daytime cooling is an emerging technology contributing to carbon-neutral heat management. Optically engineered materials with distinct absorption and emission properties in the solar and mid-infrared range are at the heart of this technology. Owing to their low emissive power of about 100 W m^-2 during daytime, substantial areas need to be covered with passive cooling materials or coatings to achieve a sizeable effect on global warming. Consequently, biocompatible materials are urgently needed to develop suitable coatings with no adverse environmental impact. It is shown how chitosan films with different thicknesses can be produced from slightly acidic aqueous solutions. The conversion to their insoluble form chitin in the solid state is demonstrated and the conversion is monitored with infrared (IR) and NMR spectroscopy. In combination with a reflective backing material, the films show below-ambient temperature cooling capabilities with a suitable emissivity in the mid-IR region and low solar absorption of 3.1-6.9%, depending on the film thickness. This work highlights the potential of chitosan and chitin as widely available biocompatible polymers for passive radiative cooling applications.

Structure Design of Polymer-Based Films for Passive Daytime Radiative Cooling

Passive daytime radiative cooling (PDRC), a cooling method that needs no additional energy, has become increasingly popular in recent years. The combination of disordered media and polymeric photonics will hopefully lead to the large-scale fabrication of high-performance PDRC devices. This work aims to study two typical PDRC structures, the randomly distributed silica particle (RDSP) structure and the porous structure, and systematically investigates the effects of structural parameters (diameter D, volume fraction fv, and thickness t) on the radiative properties of the common plastic materials. Through the assistance of the metal-reflective layer, the daytime cooling power Pnet of the RDSP structures is slightly higher than that of the porous structures. Without the metal-reflective layer, the porous PC films can still achieve good PDRC performance with Pnet of 86 W/m2. Furthermore, the effective thermal conductivity of different structures was evaluated. The single-layer porous structure with optimally designed architecture can achieve both good optical and insulating performance, and it is the structure with the most potential in PDRC applications. The results can provide guidelines for designing high-performance radiative cooling films.

Experimental Analysis of Nano-Enhanced Phase-Change Material with Different Configurations of Heat Sinks

The demand for high-performance and compact electronic devices has been increasing day by day. Due to their compactness, excessive heat is generated, causing a decrease in efficiency and life. Thermal management of electronic components is crucial for maintaining excessive heat within the limit. This experimental research focuses on the combined effect of nano-enhanced phase-change material (NePCM) with different configurations of heat sinks for cooling electronic devices. Multi-walled carbon nanotubes (MWCNTs) are used as nanoparticles with concentrations of 3 wt% and 6 wt%, RT-42 as the phase-change material (PCM), and aluminum as the pin fin heat sink material. Different configurations of the heat sink, such as circular, square, and triangular pin fins, are used against the fixed volume fraction of the fins. It is found that the square configuration has the highest heat transfer with and without PCM. A maximum base temperature reduction of 24.01% was observed in square pin fins with RT-42 as PCM. At 6 wt% of NePCM, the maximum base temperature lessened by 25.83% in the case of a circular pin fin. It is concluded from the results that a circular pin fin with NePCM is effective for base temperature reduction, and all fin configurations with NePCM collectively reduce the heat sink base temperature.

Vaccine cold chain management and cold storage technology to address the challenges of vaccination programs

The outbreaks of infectious diseases that spread across countries have generally existed for centuries. An example is the occurrence of the COVID-19 pandemic in 2020, which led to the loss of lives and economic depreciation. One of the essential ways of handling the spread of viruses is the discovery and administration of vaccines. However, the major challenges of vaccination programs are associated with the vaccine cold chain management and cold storage facilities. This paper discusses how vaccine cold chain management and cold storage technology can address the challenges of vaccination programs. Specifically, it examines different systems for preserving vaccines in either liquid or frozen form to help ensure that they are not damaged during distribution from manufacturing facilities. Furthermore, A vaccine is likely to provide very low efficacy when it is not properly stored. According to preliminary studies, the inability to store vaccine properly is partly due to the incompetency of many stakeholders, especially in technical matters. The novelty of this study is to thoroughly explore cold storage technology for a faster and more comprehensive vaccine distribution hence it is expected to be one of the reference and inspiration for stakeholders.

Combined Effects of Radiative and Evaporative Cooling on Fruit Preservation under Solar Radiation: Sunburn Resistance and Temperature Stabilization

Excessive solar radiation and high temperature often cause considerable loss and waste of fruits during transportation, retail, and storage. In the current study, a natural deep eutectic solvent-based polyacrylamide/poly(vinyl alcohol) hydrogel with nanoparticles (NPs/NADES@PAAm/PVA) is developed for fruit quality protection from solar radiation and high-temperature stress by achieving the combined effect of radiative and evaporative cooling. NPs/NADES@PAAm/PVA presents an average solar reflectance of ∼0.89 and an average emittance at the atmospheric window of ∼0.90. Besides, NPs/NADES@PAAm/PVA possesses excellent flexibility, robust mechanical strength, and good swelling behavior. The fruit preservation experiments under sunlight demonstrate that the pear (Pyrus sinkiangensis) treated with NPs/NADES@PAAm/PVA can achieve an average temperature decrease of ∼15.3 °C after sun exposure compared with the blank, and its quality-related attributes, including color, total soluble solid, relative conductivity, and respiration rate, are similar to the fresh one. Multivariate data analyses, including principal component analysis and cluster analysis, further verify that the pear treated with NPs/NADES@PAAm/PVA possesses similar quality to the fresh one after sun exposure. Thus, NPs/NADES@PAAm/PVA has promising prospects for fruit transportation, retail, and storage under solar radiation in a low-operation-cost and sustainable manner.

Passive and Dynamic Phase-Change-Based Radiative Cooling in Outdoor Weather

Radiative cooling has attracted considerable attention due to its tremendous potential in exploiting the cold reservoir of deep sky. However, overcooling always occurs in the conventional static radiative coolers because they operate only in the cooling mode in both hot and cold. Therefore, a dynamic radiative cooler based on phase change materials is highly desired. Nevertheless, the practical outdoor phase-change-based dynamic radiative cooling has not yet been experimentally demonstrated. To satisfy the stringent requirement of the phase-change-based radiative cooler in outdoor weather conditions, we engineered the phase-change material (VO₂) to possess the room-temperature phase-transition capability for typical weather conditions. Second, the reconfigurable cavity consists of the lossless spacer to ensure the magnitude of thermal modulation and suppress the solar absorption simultaneously. Third, the practical selective-filtering method is devised to shield the solar irradiance while permitting the thermal emission. Our experiment demonstrates that these materials and photonic measures can work together to realize the dynamic radiative cooling in actual weather conditions, which shows a self-adaptive switch between the ON-cooling state in hot daytime and the OFF-cooling state in cold nighttime. The study pushes the radiative cooler toward multifunctionality and provides beneficial guidance for the phase-change-based intelligent thermal control.

Fully Biobased Photothermal Films and Coatings for Indoor Ultraviolet Radiation and Heat Management

Sustainable materials are needed to mitigate against the increase in energy consumption resulting from population growth and urbanization. Here, we report fully biobased nanocomposite films and coatings that display efficient photothermal activity and selective absorption of ultraviolet (UV) radiation. The nanocomposites with 20 wt % of lignin nanoparticles (LNPs) embedded in a chitosan matrix displayed an efficient UV blocking of 97% at 400 nm along with solar energy-harvesting properties. The reflectance spectra of the nanocomposite films revealed the importance of well-dispersed nanoparticles in the matrix to achieve efficient UV-blocking properties. Finally, yet importantly, we demonstrate the nanocomposites with 20 wt % LNPs as photothermal glass coatings for passive cooling of indoor temperature by simply tailoring the coating thickness. Under simulated solar irradiation of 100 mW/cm², the 20 μm coating achieved a 58% decrease in the temperature increment in comparison to the system with uncoated glass. These renewable nanocomposite films and coatings are highly promising sustainable solutions to facilitate indoor thermal management and improve human health and well-being.

Heterothermy as the Norm, Homeothermy as the Exception: Variable Torpor Patterns in the South American Marsupial Monito del Monte (Dromiciops gliroides)

Hibernation (i.e., multiday torpor) is considered an adaptive strategy of mammals to face seasonal environmental challenges such as food, cold, and/or water shortage. It has been considered functionally different from daily torpor, a physiological strategy to cope with unpredictable environments. However, recent studies have shown large variability in patterns of hibernation and daily torpor ("heterothermic responses"), especially in species from tropical and subtropical regions. The arboreal marsupial "monito del monte" (Dromiciops gliroides) is the last living representative of the order Microbiotheria and is known to express both short torpor episodes and also multiday torpor depending on environmental conditions. However, only limited laboratory experiments have documented these patterns in D. gliroides. Here, we combined laboratory and field experiments to characterize the heterothermic responses in this marsupial at extreme temperatures. We used intraperitoneal data loggers and simultaneous measurement of ambient and body temperatures (T A and T B, respectively) for analyzing variations in the thermal differential, in active and torpid animals. We also explored how this differential was affected by environmental variables (T A, natural photoperiod changes, food availability, and body mass changes), using mixed-effects generalized linear models. Our results suggest that: (1) individuals express short bouts of torpor, independently of T A and even during the reproductive period; (2) seasonal torpor also occurs in D. gliroides, with a maximum bout duration of 5 days and a mean defended T B of 3.6 ± 0.9°C (one individual controlled T B at 0.09°C, at sub-freezing T A); (3) the best model explaining torpor occurrence (Akaike information criteria weight = 0.59) discarded all predictor variables except for photoperiod and a photoperiod by food interaction. Altogether, these results confirm that this marsupial expresses a dynamic form of torpor that progresses from short torpor to hibernation as daylength shortens. These data add to a growing body of evidence characterizing tropical and sub-tropical heterothermy as a form of opportunistic torpor, expressed as daily or seasonal torpor depending on environmental conditions.

Multiscale porous elastomer substrates for multifunctional on-skin electronics with passive-cooling capabilities

In addition to mechanical compliance, achieving the full potential of on-skin electronics needs the introduction of other features. For example, substantial progress has been achieved in creating biodegradable, self-healing, or breathable, on-skin electronics. However, the research of making on-skin electronics with passive-cooling capabilities, which can reduce energy consumption and improve user comfort, is still rare. Herein, we report the development of multifunctional on-skin electronics, which can passively cool human bodies without needing any energy consumption. This property is inherited from multiscale porous polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) supporting substrates. The multiscale pores of SEBS substrates, with characteristic sizes ranging from around 0.2 to 7 µm, can effectively backscatter sunlight to minimize heat absorption but are too small to reflect human-body midinfrared radiation to retain heat dissipation, thereby delivering around 6 °C cooling effects under a solar intensity of 840 W⋅m^-2 Other desired properties, rooted in multiscale porous SEBS substrates, include high breathability and outstanding waterproofing. The proof-of-concept bioelectronic devices include electrophysiological sensors, temperature sensors, hydration sensors, pressure sensors, and electrical stimulators, which are made via spray printing of silver nanowires on multiscale porous SEBS substrates. The devices show comparable electrical performances with conventional, rigid, nonporous ones. Also, their applications in cuffless blood pressure measurement, interactive virtual reality, and human-machine interface are demonstrated. Notably, the enabled on-skin devices are dissolvable in several organic solvents and can be recycled to reduce electronic waste and manufacturing cost. Such on-skin electronics can serve as the basis for future multifunctional smart textiles with passive-cooling functionalities.

Comparative Study of Experimental and Theoretical Evaluation of Nocturnal Cooling System for Room Cooling for Clear and Cloudy Sky Climate

Nocturnal radiation is one of the effective passive cooling technologies by infrared radiation exchange between earthly surfaces and the sky. Heating ventilation and air conditioning (HVAC) systems are highly energy-demanding and there is a need to develop alternative low-energy means to achieve comfort. Radiative cooling reduces the electricity requirements, which normally is generated through fossil fuels, in order to run active cooling systems. During the day, this is offset by solar radiation gains on the roof; however, at night, this heat loss has the ability to cool air, as roofs can experience a temperature drop of 2-12 °C below ambient. The experimental investigation of the aluminum material and their surface colors on nocturnal cooling is presented for clear and cloudy sky conditions. The material of aluminum and black color coating are considered. Results obtained reveal that the plates' performances greatly depend on the presence of clouds in the night. The best results are obtained in a clear sky summer climate condition than in the cloudy sky condition. The net cooling rate of night sky radiation system for without and with coating on aluminum of mass flow rate 0.05 kg s-1 is near about 72.30-80.99 W m-2 for clear sky and 48.75-53.25 W m-2 for cloudy sky condition.

Servo-controlled cooling during neonatal transport for babies with hypoxic-ischaemic encephalopathy is practical and beneficial: Experience from a large UK neonatal transport service

AIM

Servo-controlled therapeutic hypothermia is a routine therapy for babies with hypoxic-ischaemic encephalopathy in the neonatal unit and is delivered in designated cooling centres. It is increasingly being used during neonatal transport in the UK to deliver this therapy in a timelier manner for babies not born in a cooling centre. Prior to the implementation of this treatment, passive cooling alone was used in transport. Comparison of passive and servo-controlled cooling during neonatal transfers with reference to: (i) the proportion of babies in the therapeutic range (33-34°C) at three time points during the transport mission (arrival of the team at the referring unit, departure of the team from the referring unit and at the completion of transport); (ii) the proportion of babies overcooled at any point once the transport team was present (<33°C); and (iii) duration of phases of the transfer to evaluate the impact of active cooling on how long it takes to undertake transfer.

METHODS

This was a retrospective observational study comparing babies with passive and servo-controlled hypothermia (January 2015 to May 2016) following introduction of the servo-controlled cooling mattress.

RESULTS

A total of 48 patients were treated with hypothermia in transit (29 passive, 19 servo-controlled). The median gestational age (GA) was 40 weeks (interquartile range: 39-41) and mean birthweight (BW) 3420 g (standard deviation 600 g); there was no differences in GA, BW and clinical characteristics between the groups. There was a statistically significant difference in the temperature at the end of the transport, where 94% (n = 18) of babies who received servo-controlled cooling were in the target temperature in comparison with only 65% (n = 19) of the passive cooling group babies (P = 0.045). In addition, none of the babies in the servo-controlled group were warm (>34°C) at the end of the transfer. Babies who underwent servo-controlled cooling are more likely to maintain a target temperature (33-34°C) (17 (89%) vs. 17 (58%), P = 0.021); in particular, there is less overcooling (<33°C) in this group (2 (10%) vs. 15 (51%), P = 0.004). Total mission time was not significantly different.

CONCLUSION

The use of servo-controlled cooling devices during neonatal transport improves the ability to maintain the baby's temperature within the target range (33-34°C) with less overcooling.

The Effect of Radiative Cooling on Reducing the Temperature of Greenhouses

Currently, greenhouses are widely used for the cultivation of various crops. However, in tropical and subtropical regions, undesired near-infrared radiation (NIR) causes heat loads inside the greenhouse. Recent works have demonstrated that radiative cooling, releasing energy via radiative heat exchange where the heat is dumped directly into outer space, can be achieved by using silica particles designed to emit in the infrared atmospheric transparency window. The purpose of this study is to improve the plastic greenhouse cladding to regulate the temperature inside the greenhouse, mainly by passive cooling. Low-density-polyethylene (LDPE)-based formulations with anti-fogging agent, UV stabilizer, and silica particles were prepared by the melt blending technique and were formed into a double film by extrusion molding. Experimental results showed that under 35 &deg;C ambient conditions, the inner temperature of the simulated greenhouse with the newly developed cladding was 4 to 5 &deg;C less than that of the greenhouse with the commercial agricultural polyethylene (PE) film.

Plasmonic Glasses and Films Based on Alternative Inexpensive Materials for Blocking Infrared Radiation

The need for energy-saving materials is pressing. This Letter reports on the design of energy-saving glasses and films based on plasmonic nanocrystals that efficiently block infrared radiation. Designing such plasmonic composite glasses is nontrivial and requires taking full advantage of both material and geometrical properties of the nanoparticles. We compute the performance of solar plasmonic glasses incorporating a transparent matrix and specially shaped nanocrystals. This performance depends on the shape and material of such nanocrystals. Glasses designed with plasmonic nanoshells are shown to exhibit overall better performances as compared to nanorods and nanocups. Simultaneously, scalable synthesis of plasmonic nanoshells and nanocups is technologically feasible using gas-phase fabrication methods. The computational simulations were performed for noble metals (gold and silver) as well as for alternative plasmonic materials (aluminum, copper, and titanium nitride). Inexpensive plasmonic materials (silver, copper, aluminum, and titanium nitride) show an overall good performance in terms of the commonly used figures of merit of industrial glass windows. Together with numerical data for specific materials, this study includes a set of general rules for designing efficient plasmonic IR-blocking media. The plasmonic glasses proposed herein are good candidates for the creation of cheap optical media, to be used in energy-saving windows in warm climates' housing or temperature-sensitive infrastructure.

Multi-Objectives Optimization of Ventilation Controllers for Passive Cooling in Residential Buildings

An inappropriate indoor climate, mostly indoor temperature, may cause occupants’ discomfort. There are a great number of air conditioning systems that make it possible to maintain the required thermal comfort. Their installation, however, involves high investment costs and high energy demand. The study analyses the possibilities of limiting too high a temperature in residential buildings using passive cooling by means of ventilation with ambient cool air. A fuzzy logic controller whose aim is to control mechanical ventilation has been proposed and optimized. In order to optimize the controller, the modified Multiobjective Evolutionary Algorithm, based on the Strength Pareto Evolutionary Algorithm, has been adopted. The optimization algorithm has been implemented in MATLAB^®, which is coupled by MLE+ with EnergyPlus for performing dynamic co-simulation between the programs. The example of a single detached building shows that the occupants’ thermal comfort in a transitional climate may improve significantly owing to mechanical ventilation controlled by the suggested fuzzy logic controller. When the system is connected to the traditional cooling system, it may further bring about a decrease in cooling demand.

Passive cooling of cutaneous and subcutaneous tissues using phase changing materials: feasibility study using a numerical model

In many dermatological applications, lowering the temperature of skin and maintaining specific temperatures for extended periods of time are fundamental requirements for treatment; for example, in targeting adipose tissue and managing cutaneous pain. In this work, we investigate the feasibility of using phase changing materials (PCMs) as an alternative passive, open-loop, heat extraction method for cooling cutaneous and subcutaneous tissues. We used a finite difference parametric approach to model the spatial and temporal progression of the heat transferred from the skin to a PCM in contact with the skin surface. We modelled the thermal performance of different PCMs, including different thicknesses. In addition, we used our model to propose application strategies. Numerical simulations demonstrate the feasibility of using PCMs for extracting heat from the skin and upper fat layers, inducing and maintaining similar temperatures as those induced by active closed-loop cooling with a cold plate. In terms of development, the critical design parameters are the temperature range of solidification of the material, the thickness of the material, and the rate of melting. Our study suggests that PCM-based devices may offer an alternative skin and adipose tissue cooling method that is simple to implement and use.