The review, conducted by Anthony B. Sholanke and David Agbetoye of Covenant University in Nigeria, followed a PRISMA-informed search, screening, and thematic synthesis process. The authors identified 71 records, removed duplicates and off-topic entries, and settled on 37 studies published between 2020 and 2026, drawn from Google Scholar, the Covenant University Repository, the Multidisciplinary Digital Publishing Institute, and ResearchGate. Because the included studies varied so widely in building type, climate, and method, the authors judged a quantitative meta-analysis statistically indefensible and instead organized the evidence around three recurring themes: natural ventilation as a thermal purge mechanism, the strategic placement of thermal mass, and the integration of both with phase change materials.

The core physical logic of the strategy is straightforward. Thermal mass, in the form of concrete slabs, masonry walls, or earth-based construction, absorbs excess heat during occupied daytime hours, delaying the rise of indoor air temperature. Then, overnight, natural ventilation flushes cool outside air across those surfaces, extracting the stored heat and recharging the mass for the next day’s cycle. The review describes this as a thermal purge: the building’s fabric acts as a heat sink by day and is reset by night, potentially lowering the starting temperature of the interior each morning and reducing the burden on any mechanical cooling system.

Several mechanisms drive the purge. Cross-ventilation exploits pressure differentials between windward and leeward facades, while the stack effect, buoyancy-driven flow through solar chimneys, atria, and high-level clerestory openings, sustains airflow even on windless days. Courtyards and atria can act as the building’s lungs, breaking up deep plans and, when landscaped with vegetation or water features, pre-cooling incoming air. The authors note that institutional buildings, with their elongated plans and repetitive spatial modules, may be particularly well suited to such strategies, provided internal partitions do not obstruct the flow.

Placement of the mass matters as much as its quantity. The review emphasizes that unshaded external mass walls exposed to intense tropical sun can become heat reservoirs that radiate warmth into interiors well into the evening, increasing rather than reducing cooling loads. The recommended pattern is therefore to concentrate mass in internal partitions, floor slabs, and structural cores, kept exposed to indoor air rather than buried behind gypsum board or insulation, while external envelopes rely on shading devices, overhangs, ventilated cavities, and double-skin facades to limit solar gain before it reaches the heavy layers.

One of the most striking technical findings comes from a single simulation study included in the review, which modeled internal thermal mass under idealized cyclical design-day conditions. That study found the relationship between mass thickness and peak cooling-load reduction is nonlinear: beyond an optimum of roughly 28 to 45 millimeters for the internal mass layer, additional mass became counterproductive, presumably because the material could not be fully discharged overnight. The same study reported that granite as an internal mass material was about three times more effective than concrete of comparable thickness, and that pairing a lightweight envelope with internal mass cut peak cooling load by a further 35.9 percent. The review’s authors are explicit that this figure is an illustrative, single-study benchmark, dependent on one material, one modeling method, and one set of climate assumptions, and should not be read as a universal design rule.

Phase change materials add a modern twist to the old heavy-wall approach. Rather than storing sensible heat through high density, PCMs absorb large amounts of latent heat as they melt, offering far higher energy storage density in thin layers that can be integrated into ceiling tiles, wallboards, or floor slabs. Materials with transition temperatures near the desired indoor comfort range, around 24 to 26 degrees Celsius, can moderate the temperature spikes that would otherwise trigger air conditioning. But the review stresses that PCMs only work if they fully re-solidify overnight, a regeneration cycle that depends entirely on effective night flushing directed across the PCM-enhanced surfaces. Without that purge, the material saturates and stops performing.

The review is notably candid about the limits and contradictions in the evidence. Only 10 of the 37 included studies, about 27 percent, are directly institutional or tropical in context; the remainder are mechanistically informative but require local validation before prescriptive application. The authors also flag genuine disagreement in the wider literature about whether thermal mass works at all in climates with a narrow diurnal temperature range, a condition common in humid-equatorial settings. A field study of vernacular earth buildings in Costa Rica recorded peak-temperature damping of roughly 5 degrees Celsius in heavyweight construction, moderating but not eliminating that concern. More troubling, a Scopus- and Web of Science-indexed review found that in terraced houses in Johor Bahru, Malaysia, night flushing with high thermal mass reduced peak indoor temperature by about 2.5 degrees Celsius but did not meaningfully improve daytime comfort at 65 to 77 percent relative humidity; ceiling fans were needed to recover an additional 4 degrees of Standard Effective Temperature reduction. In other words, night flushing reliably removes stored heat, but translating that into occupant-perceived comfort in hot-humid climates may require pairing with fan-assisted air movement.

Practical barriers also loom large. Night flushing requires vents or windows to remain open and unobstructed overnight in buildings that may be unattended, raising concerns about security, weather ingress, and insects, which points toward lockable, screened ventilation hardware rather than fully open windows. Effective operation also depends on consistent control, opening vents at the right time and closing them before daytime heat begins, something the review says is poorly served by the heuristic, rule-based scheduling still common in tropical buildings. The authors point to predictive, potentially AI-driven ventilation control as a promising alternative to static schedules.

For architects and campus administrators, the review’s recommendations are framed as evidence-informed starting points rather than validated specifications: concentrate thermal mass in internal partitions and cores, keep heavy elements exposed to indoor air, use mixed-mode ventilation with night flushing to reset thermal inertia before occupancy, and deploy solar chimneys or atria to sustain buoyancy-driven purges during still periods. The authors call for longitudinal field monitoring of tropical institutional buildings integrating PCMs with night ventilation, research into bio-based phase change materials from local resources, and future systematic reviews with registered protocols, full database coverage, and formal quality appraisal. The overall message is that thermal mass and natural ventilation function best as a synergistic, context-dependent pair, a strategy whose benefits are real but whose magnitude depends heavily on climate, humidity, building type, and the discipline of the nightly purge.

Subject of Research: Integration of thermal mass and natural ventilation for passive cooling in tropical institutional buildings

Article Title: Thermal mass and natural ventilation integration for passive cooling in tropical institutional buildings: a systematic literature review

Article References: Sholanke, A. B., & Agbetoye, D. (2026). Thermal mass and natural ventilation integration for passive cooling in tropical institutional buildings: a systematic literature review. Frontiers in Energy Research, 14, Article 1974826. https://doi.org/10.3389/fenrg.2026.1974826

Image Credits: AI Generated

DOI: 10.3389/fenrg.2026.1974826

Keywords: thermal mass, natural ventilation, passive cooling, tropical climate, institutional buildings, night flushing, phase change materials, systematic review, building energy efficiency, sustainable architecture, solar chimney, thermal comfort

The core weakness of conventional AI-driven materials discovery, according to the researchers, lies in the black-box character of most end-to-end models. A neural network trained purely on input-output pairs can interpolate well within its training data, but it learns nothing about the causal mechanisms that connect a microscopic formulation to a macroscopic property. When asked to extrapolate beyond its dataset, such a model can produce physically impossible predictions. Worse still, when the design task involves multiple conflicting objectives, black-box optimizers tend to wander into local optima, missing the true best solutions entirely. PHICS, short for a physics-constrained inverse design system, was built to overcome precisely these limitations by embedding physical law into the architecture of the model itself rather than hoping the data will reveal it.

The structural backbone of PHICS is a directed acyclic graph, a topology in which information flows in one direction only and no circular dependencies exist. This choice is not merely computational convenience; it enforces a transparent causal chain that mirrors the actual multiscale hierarchy of a composite material. At the base of the chain sits microscale composition, the choice of fillers, matrix materials, and additives. These determine mesoscale interfaces, the thin regions where different phases meet and where heat and charge carriers must pass. Interfaces in turn shape multiphase networks, the connected pathways that span the bulk material, and those networks ultimately dictate macroscale functional properties such as thermal conductivity, electrical resistivity, and latent heat capacity. By decoupling the problem into this explicit sequence, PHICS retains the fitting efficiency of data-driven regression while strictly adhering to fundamental conservation laws and boundary constraints at every step.

This architecture yields a practical benefit that pure machine learning cannot match: superior extrapolation and generalization fidelity. Because each link in the causal graph is constrained by physics, the framework can make credible predictions in regions of the design space where experimental data are sparse or absent. That capability matters enormously for inverse design, the task of working backward from a desired set of properties to the formulation and microstructure that will deliver them. Inverse design is mathematically demanding because the mapping from properties back to parameters is rarely unique and the search space is high-dimensional. PHICS addresses this by coupling its physics-causal surrogate model with NSGA-II, the non-dominated sorting genetic algorithm II, a well-established evolutionary optimizer designed for multi-objective problems.

The choice of NSGA-II reflects the mathematical character of the problem. When a material must simultaneously optimize several conflicting properties, the set of best possible solutions forms a Pareto front, a surface in performance space where no objective can be improved without sacrificing another. For composite phase-change materials, this front is complex and non-convex, meaning that simple weighted combinations of objectives can easily steer an optimizer into a local optimum that looks good but falls far short of the true frontier. Traditional trial-and-error experimentation fares even worse, requiring exhaustive synthesis campaigns to map even a fraction of the design space. By contrast, the PHICS-plus-NSGA-II combination performs high-throughput evaluations within seconds and carries out high-precision inversion of optimal microstructural parameters across high-dimensional, non-convex target spaces, tracing the Pareto front with a completeness that manual methods cannot approach.

The framework was put to a demanding practical test: the design of graphite fiber and n-octacosane composite phase-change materials intended for the thermal management of high-power electronics. N-octacosane, a paraffin wax, offers excellent latent heat storage, but on its own it conducts heat poorly. Graphite fibers provide conductive highways for thermal transport, yet graphite is also electrically conductive, which creates a serious risk of short circuits in dense electronic assemblies. Guided by the inverse design output of PHICS, the team introduced an ultrathin amorphous alumina interface transition layer precisely at the boundaries between the graphite fibers and the paraffin matrix. This nanoscale intervention was not an arbitrary choice but a direct product of the framework’s causal reasoning about how interface engineering propagates through the multiscale chain to affect final properties.

The amorphous alumina layer performs a remarkable double duty. It acts simultaneously as a phonon transmission bridge and an electron insulation barrier. Phonons, the quantum vibrations that carry heat in non-metallic solids, can pass across the alumina layer with acceptable resistance, so the graphite fibers retain their ability to spread heat rapidly through the composite. Electrons, by contrast, are blocked by the insulating alumina, so the composite as a whole remains electrically resistive even though it contains a conductive filler. The result is a concurrent leap in both thermal conductivity and electrical resistivity while preserving high latent heat storage density. In effect, the design breaks the long-standing seesaw effect among competing properties, achieving simultaneous enhancements that traditional formulation strategies had treated as mutually exclusive.

Beyond the specific material achievement, the work establishes a methodological paradigm that its authors describe as a full closed loop spanning multiscale inverse design and experimental validation. The loop runs from physics-constrained modeling through multi-objective inverse optimization to synthesized materials and back to measured performance, allowing the model to be refined against reality rather than against assumptions. Leveraging interface, phase, and carrier engineering in combination, the approach demonstrates how causal structure and evolutionary search can be woven together to navigate design spaces that overwhelm both human intuition and conventional optimization. The researchers suggest that this paradigm of physics-constrained modeling coupled with multi-objective inverse optimization paves a pathway for the intelligent inverse design of next-generation functional composites well beyond thermal management.

The study was conducted by researchers led by Professors Shih-Chi Chen, Jianbin Xu, and Ni Zhao of The Chinese University of Hong Kong, with support from the Centre for Heterogeneous Integration and Production under SEAM@InnoHK, the third InnoHK research cluster of the Hong Kong Special Administrative Region. The centre is dedicated to advancing next-generation electronics through innovations in semiconductor equipment and materials processing powered by heterogeneous integration technologies, a mission that aligns closely with the thermal management needs the new materials address. As electronic devices continue to concentrate power into ever smaller volumes, the ability to design materials that conduct heat, block current, and store thermal energy all at once may prove essential, and PHICS offers a blueprint for finding such materials not by accident but by design.

Subject of Research: Physics-constrained machine learning for the inverse design of multifunctional composites

Article Title: Physics-constrained machine learning for the inverse design of multifunctional composites

Article References: Physics-constrained machine learning for the inverse design of multifunctional composites. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Physics-constrained, machine, learning, inverse, design, multifunctional, composites, scientific research

The new review, led by researchers applying the PRISMA methodology to 163 peer-reviewed articles published between 2004 and 2024, maps two decades of transformation in how heat is generated, stored, recovered, and managed. Its central finding is striking: the field is no longer evolving along a single technological track. Instead, traditional thermodynamic machinery is being fused with renewable generation, advanced materials, and a suite of digital tools that would have seemed like science fiction to the engineers who designed the first large steam plants. The authors argue that this convergence represents not merely incremental improvement but a paradigm shift in how thermal energy fits into a decarbonized world.

Among the most consequential advances documented in the review is the rise of digitalization. Artificial intelligence, machine learning, the Internet of Things, and digital twin technologies have moved from academic curiosities to operational necessities in modern thermal plants. Digital twins, virtual replicas of physical systems that update in real time with sensor data, allow operators to simulate operating conditions, predict component failures before they occur, and fine-tune performance continuously. In pilot projects analyzed by the review, these tools improved overall system efficiency by 20 to 35 percent and reduced unplanned downtime by up to 40 percent. For an industry where a single day of turbine outage can cost millions, those margins translate directly into both economic and emissions savings.

Predictive maintenance deserves particular attention in this digital story. Traditional thermal plants have historically relied on scheduled inspections and reactive repairs, a model that wastes resources when components are healthy and risks catastrophic failure when they are not. Machine learning models trained on vibration, temperature, and pressure data can now flag degradation patterns invisible to human operators, scheduling interventions precisely when they are needed. Adaptive control systems go further, adjusting combustion parameters, steam conditions, and heat distribution in real time to match fluctuating demand and variable renewable input. The review’s authors emphasize that this adaptive capability becomes essential as thermal systems increasingly share the grid with intermittent solar and wind generation.

Waste heat recovery represents another frontier where the review documents remarkable progress. Industrial processes routinely reject enormous quantities of low- to medium-grade heat that conventional steam cycles cannot economically capture. Organic Rankine cycles, which substitute organic working fluids for water to exploit lower temperature differences, and thermoelectric generators, which convert heat directly into electricity through solid-state semiconductor junctions, have matured dramatically. The review reports that these technologies now achieve energy recovery efficiencies exceeding 80 percent for suitable heat streams, transforming what was once industrial exhaust into a meaningful power resource. This matters because waste heat is ubiquitous: data centers, cement kilns, glass furnaces, and even refrigeration systems all radiate recoverable energy around the clock.

Energy storage, long the weak link of renewable integration, is undergoing its own thermal renaissance. Phase change materials, which absorb and release large amounts of latent heat as they transition between solid and liquid states, allow thermal systems to bank energy far more cheaply than electrochemical batteries in many applications. Thermochemical storage, which binds energy in reversible chemical reactions, promises even higher energy densities for long-duration storage. Nano-enhanced composites address the historical Achilles heel of these media, namely poor thermal conductivity, by embedding nanoscale additives that accelerate heat transfer into and out of the storage medium. The review highlights these material innovations as critical enablers for storing solar heat overnight and smoothing the output of concentrated solar power plants.

Hybridization is emerging as the architectural principle that ties these threads together. The review documents configurations that integrate biomass boilers, concentrated solar power, and photovoltaic-thermal systems, which generate electricity and useful heat simultaneously from the same solar footprint. Such hybrids exploit the complementary strengths of each technology: biomass provides dispatchable heat when the sun sets, CSP delivers high-temperature thermal energy that can drive efficient turbines, and PVT collectors maximize the yield of every square meter of collector area. The authors note that these multi-source designs also enhance energy security, reducing dependence on any single fuel or technology and insulating communities from supply shocks.

Perhaps the most socially resonant findings concern modular and containerized thermal solutions for decentralized applications. In agriculture, compact thermal units that provide controlled drying and cooling environments reduced post-harvest losses by up to 30 percent, a figure with profound implications for food security in developing regions where a third or more of crops can spoil before reaching market. In sub-Saharan Africa, solar-driven thermal cold chain systems improved vaccine storage reliability by more than 50 percent, a capability that proved decisive during recent immunization campaigns. These deployments demonstrate that thermal innovation is not confined to gigawatt power stations; it is reaching clinics, farms, and villages that the central grid has never reliably served.

The review also positions thermal systems within the broader multi-vector energy landscape of the coming decades. Integration with electrochemical storage and green hydrogen pathways places heat at the core of decarbonized platforms rather than at their margins. Excess renewable electricity can drive electrolysis to produce hydrogen, which is then burned or used in fuel cells to generate heat on demand, effectively converting thermal plants into flexible buffers for the entire energy system. Conversely, high-temperature thermal storage can feed industrial processes that electrification alone cannot serve economically, such as cement clinker production and steel reheating. The authors argue that this bidirectional flexibility is precisely what Paris Agreement pathways require.

Looking forward, the review identifies interdisciplinary research, advanced material innovation, particularly in nanostructured composites, and supportive regulatory frameworks as the three pillars that will define the next phase of thermal energy development. The transition toward intelligent, low-carbon thermal networks, the authors conclude, reflects not only technological evolution but a fundamental rethinking of the role heat plays in a sustainable society. Two decades of documented progress suggest the engineering community has already proven the concept. The remaining challenge, as with so much of the energy transition, is scaling proven innovations from pilot projects to the global infrastructure that still runs on the steam cycles of the last century.

Subject of Research: Thermal energy systems innovation

Article Title: Innovations in thermal energy systems, bridging traditional and emerging technologies for sustainable energy solutions

Article References: Eze, V. H. U. (2025). Innovations in thermal energy systems, bridging traditional and emerging technologies for sustainable energy solutions. Frontiers in Thermal Engineering, 5, Article 1654815. https://doi.org/10.3389/fther.2025.1654815

Image Credits: AI Generated

DOI: 10.3389/fther.2025.1654815

Keywords: thermal energy systems, digital twins, waste heat recovery, phase change materials, concentrated solar power, green hydrogen, energy transition, Innovations, thermal, energy, systems, bridging

The thermal problem begins with a deceptively simple mechanism. During every charge and discharge cycle, current flowing through the electrolyte and electrode materials encounters the equivalent series resistance, or ESR, generating Joule heat inside the cell. That internal heat accumulates, and at elevated temperatures it accelerates the decomposition of electrolytes and electrodes, speeds up self-discharge, and in extreme cases can trigger electrolyte breakdown, gas evolution, or even thermal runaway. Cold is no friend either: at low temperatures, ionic conductivity in the electrolyte drops, viscosity rises, and the accessible capacitance shrinks. The result is a bidirectional thermal challenge in which both extremes of the operating envelope degrade performance, just through different mechanisms.

What makes the review particularly timely is a counterintuitive discovery from recent research. Li and colleagues identified a negative Joule heat effect in supercapacitor modules under specific conditions, namely high-frequency charge-discharge cycling at low current densities in multi-cell configurations. In other words, under certain operating regimes the modules do not simply heat up as expected, adding a layer of complexity to thermal behavior prediction that existing models struggle to capture. This phenomenon underscores how much remains unknown about heat generation in devices that are often assumed to be thermally simpler than batteries.

The degradation story is told at the level of individual components. Electrolytes, which transport ions between electrodes, follow Arrhenius-type behavior in which ionic conductivity increases with temperature, but only up to a point: at high temperatures, decomposition, solvent evaporation, and rising internal pressure take over. Organic electrolytes typically operate between roughly 233 K and 343 K, aqueous systems between 273 K and 333 K, while ionic liquids can function up to about 450 K, making them increasingly attractive for high-temperature applications. Electrodes made of activated carbon or carbon nanotubes face their own thermal limits, and the binders that hold them together, such as polyvinylidene fluoride, can soften or melt, causing delamination between active material and current collectors. Separators, the ion-permeable membranes between electrodes, can lose structural integrity at high temperatures, risking short circuits, while below about 243 K ion mobility through their pores becomes severely restricted.

The aging mechanisms are particularly insidious because they feed on themselves. High temperatures generate gases such as hydrogen and carbon monoxide that build internal pressure, sometimes venting through safety valves before the conventional 20 percent capacitance-loss end-of-life threshold is even reached. Solid decomposition products block the pores of the carbon electrodes, reducing the effective surface area and thus capacitance. Joule heating accelerates electrochemical degradation, which raises ESR, which in turn generates more Joule heat, a positive feedback loop that progressively elevates internal temperature. Current collectors oxidize at high temperatures, increasing contact resistance, and acetonitrile-based cells have been reported to lose roughly 25 percent of their weight through electrolyte evaporation after 12,000 seconds at 3 V and 343 K, an accelerated stress condition well beyond normal operating limits.

Against this backdrop, the review evaluates the arsenal of thermal management strategies, dividing them into passive and active systems. Passive approaches, which consume no parasitic electrical energy, include natural convection, heat pipes, and phase change materials, or PCMs. Heat pipes exploit a closed two-phase cycle in which a working fluid evaporates at the hot end and condenses at the cool end, achieving near-isothermal heat transport. In supercapacitor-specific experiments, heat pipe cooling reduced peak cell temperature by 7.5 to 11.7 percent and improved capacitance retention by about 2.1 percent compared with natural convection. PCMs, typically paraffin wax with melting points in the 303 to 333 K range, absorb latent heat during high-power bursts and release it during rest, buffering temperature excursions, though their low intrinsic thermal conductivity of 0.1 to 0.3 watts per meter-kelvin limits heat transfer rates unless enhanced with metal foams, fins, or conductive meshes.

Active systems trade simplicity for performance. Forced air cooling is the most widely implemented active approach, and careful engineering pays dividends: Voicu and colleagues found that a staggered module with cell spacing of 1.25 times the cell diameter optimizes heat removal, while Soltani and colleagues identified an optimal air speed of 5 meters per second and 5-millimeter spacing for a 12-cell lithium-ion capacitor module, with predicted and measured temperatures agreeing within 2 K. Liquid cooling, with water’s thermal conductivity roughly 25 times that of air, offers the highest heat removal capacity, achieving up to 35 percent lower maximum temperatures in supercapacitor-specific experimental studies. But it brings complexity, weight, sealing requirements, and leakage risks. The most striking results come from hybrid systems: combining PCMs with heat pipes achieved approximately 35 percent lower peak cell temperatures and 86 percent lower temperature non-uniformity than PCM-only cooling, a configuration well matched to the burst-and-rest duty cycles that characterize supercapacitor applications.

The review does not shy away from the field’s shortcomings. The authors identify critical research gaps, including limited understanding of molecular-level degradation mechanisms, an absence of standardized testing protocols that would make results from different laboratories directly comparable, and insufficient development of cost-effective thermal interface materials. The numbers are telling: thermal interface resistance between cells and aluminum cold plates is estimated at 10 to 50 K cm²/W for commercial silicone pads, comparable in magnitude to the cell-level thermal resistance itself. Meanwhile, the longest calendar aging studies span only 12 to 18 months, yet the Arrhenius rule is routinely used to project 10-to-15-year lifetimes, an extrapolation of nearly an order of magnitude beyond validated data.

The future directions the authors outline are equally concrete. They call for hybrid and adaptive thermal management systems that co-optimize PCM melting point, layer thickness, heat pipe geometry, and condenser configuration as a coupled system, along with adaptive control strategies that modulate cooling intensity based on real-time temperature and state-of-health estimates. They also highlight the need for non-invasive in-situ temperature mapping, noting that although the electrode is the dominant thermal resistance in supercapacitor stacks, nearly all reviewed studies measure surface temperature only, leaving internal gradients to be inferred from models. Fiber Bragg grating-based internal temperature mapping of a 20-cell module during fast cycling, with spatial resolution of 5 millimeters or better, is proposed as a measurable milestone.

For engineers designing the next generation of energy storage, the message is clear: no single cooling approach is universally optimal, and the choice depends on power density, available volume, cost constraints, and operating temperature range. As supercapacitors push into ever more demanding roles, from regenerative braking to grid-scale stabilization, the invisible battle against heat will increasingly determine whether these remarkable devices fulfill their potential. The Wichita State team’s synthesis provides both a warning and a blueprint, showing that thermal management is not an afterthought but a first-order design constraint for the future of high-power energy storage.

Subject of Research: Thermal management strategies and temperature effects in supercapacitors

Article Title: Thermal management of supercapacitors: a review of thermal challenges, management strategies, future directions

Article References: Atayo, A., Subeshan, B., Asmatulu, E., & Rahman, M. (2026). Thermal management of supercapacitors: a review of thermal challenges, management strategies, future directions. Frontiers in Thermal Engineering, 6, Article 1783912. https://doi.org/10.3389/fther.2026.1783912

Image Credits: AI Generated

DOI: 10.3389/fther.2026.1783912

Keywords: supercapacitors, thermal management, Joule heating, phase change materials, heat pipes, liquid cooling, electrolyte degradation, thermal runaway, aging mechanisms, lithium-ion capacitors, energy storage, cooling systems

The review, led by Elisa Y. M. Ang of the Singapore Institute of Technology together with Aminu Yusuf of Istanbul University-Cerrahpasa and colleagues, is unusual in that it unites two research streams that are typically treated in isolation: personal cooling devices that chill the skin directly, and large-scale alternatives to the vapor-compression systems that dominate buildings. Database searches reveal an exponential increase in publications on human cooling technology, reflecting a rapidly growing field driven by climate realities. Even with dramatic emissions cuts, climate scientists widely agree that dangerous levels of heat and humidity are likely to become more common, making sustainable cooling a survival issue rather than a luxury.

Conventional air conditioning is an especially wasteful way to keep people comfortable. Because cooling is delivered to entire rooms, up to 70 percent of the energy can be wasted on empty space rather than human bodies. Personal cooling devices, or PCDs, promise to sidestep this inefficiency by targeting the skin itself, and they can also provide relief where air conditioners cannot follow, from construction sites and sports fields to outdoor medical settings. Yet the technology remains immature. To ground their assessment, the authors conducted a medium-scale market and user survey in which 56 participants evaluated three commercial products: a fan-based vest, a flow thermoelectric vest, and an ice-packed vest.

The thermoelectric vest, which exploits the Peltier effect to produce solid-state, tunable cooling, received the highest overall satisfaction rating at 3.93 out of 5. By contrast, the ice-packed vest was repeatedly described as heavy and uncomfortable because of condensation buildup, while the fan vest offered limited cooling and raised safety concerns about exposed blades. Even the best-performing device suffered from roughly three hours of battery life, high production costs, and added weight, which is a serious drawback for outdoor or industrial workers who need continuous cooling across a full shift. The authors caution that their survey was limited in sample size and trial duration, so the findings should not be overgeneralized, but the conclusion aligns with prior evaluations: no commercial personal cooling device is yet adequate as a stand-alone replacement for space cooling.

On the passive side of the field, however, remarkable progress is emerging from materials science. Phase change materials such as paraffin waxes and hydrated salts absorb body heat as they melt, sustaining cooling for up to two hours in optimized vests, though low thermal conductivity, leakage, and long recharge times remain obstacles. Evaporative approaches, which exploit water’s high latent heat, struggle in humid climates and leave wearers wet. The most striking advances come from radiative cooling textiles. Human skin, with an emissivity above 0.95, radiates heat in the mid-infrared range of 7 to 14 micrometers, and engineered fabrics can amplify this pathway. One bioinspired metafabric with a dual-gradient Janus design achieves 99.4 percent solar reflectance and 0.94 mid-infrared emittance, delivering a 17.8 degrees Celsius skin temperature reduction under intense sunlight while wicking sweat at a rate of just 0.5 milliliters per hour.

Smart fabrics are also learning to adapt. A sandwich-structured nanofibrous textile reported in 2025 combines a cooling side with 97.9 percent solar reflectance and a heating side made of carbon nanotubes absorbing 88.4 percent of sunlight; flipping the fabric switches between modes. Other designs draw inspiration from the Namib Desert beetle, using circular and triangular patterns to transport sweat continuously and reducing skin temperature by 1.3 degrees Celsius compared with cotton. Thermochromic fabrics that reflect sunlight and reverse moisture transport under hot conditions point toward garments that respond dynamically to the environment rather than offering static regulation. Meanwhile, thermoelectric garments are being rebuilt for the body: multi-stage coolers, flexible heatsinks made from hydrogel and nickel foam, and paraffin-graphene composites have demonstrated sustained on-skin cooling of 7 to 11 degrees Celsius, though the underlying bismuth telluride materials are nearing their efficiency limits and new compounds such as n-type PbS are being explored.

Because personal devices cannot yet replace whole-building cooling, the review devotes equal attention to the supply side. Here the verdict is sobering: quantitative comparisons of fourteen space-cooling technologies found vapor-compression still superior in coefficient of performance, exergetic efficiency, and power density, and it retains the highest overall sustainability score when scalability and maturity are counted. The realistic near-term path is therefore greener refrigerants, including flammable hydrocarbons like R290 and R600, alongside emerging cycles that must close the efficiency gap. Solid-state options include magnetocaloric cooling, which exploits temperature changes in gadolinium-family alloys under varying magnetic fields; electrocaloric cooling, based on dielectric materials responding to electric fields; and elastocaloric cooling, in which shape-memory alloys like nickel-titanium release and absorb latent heat under mechanical stress. All are refrigerant-free but remain limited by material costs, fatigue, and modest temperature spans.

Among the more promising newcomers, membrane heat pumps stand out. Identified by the U.S. Department of Energy in 2014 as one of the top three technologies for high energy savings, they separate moisture from air across water-vapor-selective membranes, avoiding the heavy condensation penalty of conventional systems and using only water as the working medium. Thermodynamic models suggest a potential coefficient of performance between 10 and 40, though prototypes currently achieve less than 3 due to vacuum pump inefficiencies, and even a 10 percent drop in water vapor rejection pushes performance below 3. Radiant cooling, which chills occupants directly through temperature-controlled surfaces rather than conditioning air, has demonstrated energy savings up to 50 percent and is already installed in landmark buildings such as the Pearl River Tower in Guangzhou, though condensation in humid climates remains the central engineering challenge.

Complementary, city-scale strategies multiply these gains. District cooling systems, proven in the Gulf Cooperation Council region where air conditioning consumes up to 70 percent of Saudi household electricity, achieve coefficients of performance of 4 to 6 and cut energy use by 30 to 50 percent through load sharing, and fifth-generation networks with bidirectional heat exchange can save up to 40 percent of electricity. Snow storage in Sweden, Norway, and Japan offers free seasonal cooling, while cool roofs stay 28 to 33 degrees Celsius cooler than traditional surfaces and green infrastructure intercepts 70 to 90 percent of incoming solar radiation through canopy shade, with building energy savings of 20 to 80 percent. In Singapore’s Cool Canyon experiments, cool surfaces cut sensible heat release by 30 percent and lowered afternoon air temperature by up to 2 degrees.

The review’s integrated perspective carries clear implications. For engineers, hybrid strategies combining localized and space-based cooling can deliver meaningful savings without sacrificing comfort. For manufacturers, the priorities are durability, flexibility, and heat rejection in wearables, whose performance is still measured by standards designed for uniform indoor environments and which often overestimate real-world cooling. For policymakers, the authors argue, localized cooling needs its own tailored standards, alternative technologies belong in energy codes, and district-scale low-carbon infrastructure deserves targeted incentives. Achieving this will require broader field trials, standardized evaluation metrics, and life-cycle assessments to bridge the gap between laboratory demonstrations and deployable, climate-resilient cooling.

Subject of Research: Alternative personal and space cooling technologies for sustainable thermal comfort

Article Title: Human cooling solutions: alternatives to conventional cooling solutions

Article References: Ang, E. Y. M., Yusuf, A., Soh, C. B., & Wang, P. C. (2026). Human cooling solutions: alternatives to conventional cooling solutions. Frontiers in Thermal Engineering, 6, Article 1602847. https://doi.org/10.3389/fther.2026.1602847

Image Credits: AI Generated

DOI: 10.3389/fther.2026.1602847

Keywords: human cooling, personal cooling devices, radiative cooling, thermoelectric cooling, vapor compression, solid-state cooling, membrane heat pumps, district cooling, urban heat island, phase change materials, cooling fabrics, thermal comfort

The numbers tell a striking story. A Scopus search for publications on Pickering emulsions shows year-on-year growth since 2000, peaking at 1,366 papers in 2025. The appeal is easy to understand: Pickering emulsions are simple to prepare, remarkably stable, and versatile across applications ranging from catalysis and filtration membranes to drug delivery, antibacterial coatings, cosmetics, nutraceuticals, and food technology. What the Mexican team, Miguel Rosales-Guzmán, María Esther Treviño Martínez, and Enrique Saldívar-Guerra, add to this crowded literature is a dual focus that has been largely missing until now. Their review concentrates specifically on stabilizers drawn from carbon allotropes and carbon-rich materials, and it devotes unusual attention to emulsion polymerization, the industrial workhorse process in which monomers are polymerized inside emulsion droplets to produce the latexes behind countless commercial and high-tech polymers.

The physics underlying Pickering stabilization is elegant. Solid particles that are partially wetted by both oil and water lodge themselves at the oil-water interface, where they form a mechanical barrier. The decisive parameter is the three-phase contact angle at the point where particle meets interface. If that angle is below 90 degrees, the particle is more hydrophilic and favors oil-in-water emulsions; above 90 degrees, it is more hydrophobic and favors water-in-oil systems. If a particle is completely wetted by either phase, stabilization fails entirely. Crucially, the energy required to rip a particle off the interface is typically far higher than thermal energy, which is why Pickering emulsions can be dramatically more stable than their surfactant-stabilized cousins. For spherical particles, this detachment energy scales with the square of the particle radius and the interfacial tension, and analogous expressions exist for disk-like and rod-shaped particles, geometries that matter greatly when the stabilizers are flat graphene sheets.

That is where graphene oxide enters the picture. Pristine graphene and carbon nanotubes are stubbornly hydrophobic, but oxidizing graphite to graphene oxide grafts hydroxyl and epoxy groups across the planar surface and carboxyl groups mainly at the flake edges. The result is a material that is broadly hydrophilic with localized hydrophobic zones, an inherently amphiphilic character that makes it naturally suited to stabilizing oil-in-water emulsions. Even better, those oxygen-bearing functional groups are chemical handles: researchers can attach hydrophobic alkyl amines, polymers, surfactants, or inorganic nanoparticles to tune the wettability for whatever emulsion type a given application demands. The review highlights how the degree of oxidation itself shifts the contact angle, with reported values of 63.6, 55.8, and 90.6 degrees corresponding to different oxygen-to-carbon ratios, giving formulators a dial they can turn.

The functionalization toolbox is impressively broad. A redox reaction between graphene oxide and ferrous ions decorates the sheets with magnetic iron oxide nanoparticles, while treatment with chloroauric acid yields gold-decorated hybrids. One-pot hydrothermal routes can simultaneously reduce graphene oxide to graphene and graft amine groups from polyacryloyl hydrazide, producing stabilizers for olive oil and n-decane emulsions. Ball milling offers a scalable alternative, and pyrolyzing citric acid at 200 degrees Celsius in air generates hydrophilic graphene quantum dots just nanometers across, which can then be functionalized with amines to stabilize dodecane-in-water emulsions or with histidine for styrene-in-water systems. Carbon nanotubes, meanwhile, can be tamed with oxygen plasma or nitric acid oxidation. Selective modification can even produce Janus particles with two chemically distinct faces, an asymmetry prized for interfacial work.

The most conceptually intriguing section of the review concerns polymerization inside graphene oxide-stabilized emulsions. In conventional emulsion polymerization, water-soluble initiators generate radicals that enter monomer-swollen particles, and the compartmentalization of radicals, at most one per particle at any time, governs the kinetics and molecular weights. But in the reported graphene oxide systems, the initiator of choice has been AIBN, which dissolves in the organic phase, hinting that the mechanism may resemble miniemulsion polymerization instead. The large graphene oxide platelets cloaking each droplet may also impede radical exchange between phases. The authors are candid that the mechanism remains an open question, noting that most published studies vary only one or two parameters and use inconsistent emulsion preparation methods, making firm conclusions impossible. What is clear is that the approach works: polystyrene microspheres sheathed in graphene oxide platelets have been produced since the end of the first decade of this century, and polymerizations have focused mainly on styrene and methyl methacrylate.

The applications catalogued in the review read like a tour of modern materials science. Phase-change materials such as paraffins can be encapsulated with extraordinary efficiency; one system using 7.4 weight percent graphene oxide achieved 100 percent encapsulation and a thermal conductivity of 1.3 watts per meter-kelvin for personal thermal management textiles. Self-healing coatings exploit graphene oxide microcapsules that rupture to release healing agents, with one epoxy system reducing concrete’s capillary water absorption by 98.3 percent. Freeze-drying emulsions yields porous aerogels for pressure sensors, electromagnetic interference shielding composites reach 41.4 decibels of shielding effectiveness, catalytic desulfurization systems remove 97 percent of sulfur from fuel oil, and graphene oxide quantum dots have even served as adjuvants boosting immune responses to a Chlamydia trachomatis vaccine. Each droplet can act as a nanoreactor, as demonstrated by the synthesis of 2-aminothiazole with isolated yields of 85 to 90 percent.

Among carbon-based stabilizers, the hierarchy is unambiguous. Graphene oxide dominates, accounting for more than 75 percent of recent literature entries, followed by other graphene derivatives, carbon nanotubes, and carbon quantum dots. The reasons are practical: graphene oxide is comparatively easy to prepare, inherently amphiphilic, and endlessly modifiable. Carbon nanotubes, despite their industrial maturity driven largely by lithium-ion battery electrodes, are harder to synthesize reproducibly and require more elaborate chemistry to become amphiphilic. Production costs for graphene derivatives and nanotubes remain relatively high but are expected to fall over the next five to ten years as volumes increase, and because these stabilizers are used in small proportions, cost may not be prohibitive for many emulsion applications.

Challenges remain, and the review does not shy away from them. The single greatest obstacle to real-world deployment is scaling up graphene oxide production so that the material performs reproducibly as a stabilizer, since current processes suffer significant batch-to-batch variability. Toxicity is another open question: carbon nanomaterials show varying toxicity depending on dimensions, surface modification, and purity, with nanotubes appearing potentially more harmful than graphene derivatives, though surface modification seems to attenuate the risk. The environmental fate of these materials at end of life has been largely overlooked. The authors argue that future research must pivot from proof-of-concept toward practical implementation, with attention to scalability, efficiency, and recyclability, and that unraveling the polymerization mechanism and the self-assembly processes that govern final material properties will require systematic studies across monomer types, oxidation degrees, sheet sizes, and temperatures. For a field that grew from a century-old curiosity into a 1,366-papers-a-year enterprise, the next chapter will be written not in the laboratory alone but in the pilot plant.

Subject of Research: Pickering emulsions stabilized by graphene oxide and other carbon-rich particles, including their use in emulsion polymerization and applications

Article Title: Pickering emulsions: emulsion polymerization and systems stabilized with carbon allotropes or carbon-rich materials

Article References: Rosales-Guzmán, M., Treviño Martínez, M. E., & Saldívar-Guerra, E. (2026). Pickering emulsions: emulsion polymerization and systems stabilized with carbon allotropes or carbon-rich materials. Frontiers in Soft Matter, 6, Article 1908524. https://doi.org/10.3389/frsfm.2026.1908524

Image Credits: AI Generated

DOI: 10.3389/frsfm.2026.1908524

Keywords: Pickering emulsions, graphene oxide, emulsion polymerization, carbon nanotubes, graphene quantum dots, colloids, interfacial science, phase change materials, self-healing coatings, aerogels, drug delivery, nanomaterials

In a review published in Frontiers in Photonics, Ranjeet Dwivedi, Charles Pourny, Anthony Albanese and colleagues from INSA Lyon, CNRS-Université Bourgogne Europe, CEA-LETI and the University Grenoble Alpes survey recent advances in photonic devices that integrate phase-change materials, with an eye toward neuromorphic computing—computing architectures inspired by the brain. Their central claim is bold: PCMs are not merely an optional tuning layer on photonic chips, but a key enabling material that bridges photonics’ high-throughput compute capability with the dense, persistent, low-energy programmability that practical AI hardware demands.

Photonics has long been touted as an attractive route around the energy problem. Optical signals propagate with very high bandwidth, low latency, and inherent parallelism through wavelength, spatial, and temporal multiplexing. These properties have motivated optical neural networks, photonic matrix-vector multiplication engines, and photonic tensor cores as potential accelerators for the linear-algebra operations that dominate inference and signal-processing workloads. But a central challenge remains: practical photonic processors require dense, programmable, reliable, and energy-efficient memory elements to store weights, biases, routing states, and calibration parameters directly inside the photonic circuit. Thermo-optic or free-carrier-based photonic circuits must be continuously powered to hold a given configuration, creating a static energy overhead that grows with system size.

Phase-change materials solve this missing memory problem in a striking way. Chalcogenide PCMs such as GeSbTe (GST), GeSbSeTe (GSST), Sb2S3 and Sb2Se3 exhibit large, reversible changes in optical refractive index and absorption between their amorphous and crystalline states. Crucially, these states are nonvolatile: once programmed, the optical state is retained without continuous electrical power. This makes PCM-based devices especially relevant for photonic computing, where many synaptic weights must remain fixed during inference while optical signals perform matrix-vector multiplication operations at high speed. Demonstrations have already shown PCM-based photonic in-memory computing, all-optical neurosynaptic systems, integrated photonic memories, and photonic tensor cores combining PCM weight banks with wavelength multiplexing.

The review begins with the materials science. Metavalent bonding (MVB) has been identified as a distinctive bonding mechanism that characterizes the crystalline phase of PCMs, placing them between covalently bonded and metallically bonded materials. Materials exhibiting metavalent bonding possess a characteristic set of features, including a high optical dielectric constant, enhanced chemical bond polarizability reflected by large Born effective charges, strong lattice anharmonicity associated with high Grüneisen parameters, and moderate electrical conductivity. From an optical perspective, PCMs exhibit significant differences between their amorphous (covalent) and crystalline (metavalent) phases, which is why they have long served as the working medium of optical data storage technologies such as CD-RW, DVD-RAM, and Blu-ray disks. The amorphous phase is obtained by heating the material above its melting temperature and then rapidly quenching it; the crystalline phase is achieved by annealing above the crystallization temperature, followed by slow cooling.

Among all PCMs, Ge2Sb2Te5 (GST225) is the most extensively studied. Located on the GeTe–Sb2Te3 pseudo-binary line of the Ge–Sb–Te ternary phase diagram, GST225 crystallizes at approximately 150–180 °C and offers a large refractive index contrast across the visible, near-infrared, and mid-infrared spectral ranges. At the telecommunication wavelength of 1550 nm, however, crystallization also increases the extinction coefficient by about an order of magnitude, leading to high optical losses. To evaluate and compare different PCMs for photonic applications, the researchers employ a material figure of merit (FOM) that quantifies the trade-off between optical modulation efficiency and insertion losses. Conventional GST225 thin films exhibit a FOM of approximately 2 at 1550 nm, while GeTe reaches 6.2 and Sb2S3 4.2. A distinct class of ultra-low-loss PCMs such as Sb2S3 and Sb2Se3 keeps the extinction coefficient close to zero in both states, though with a substantially smaller refractive index contrast attributed to their predominantly covalent bonding character.

The most intriguing materials lie at the border between covalent and metavalent systems: the GeSe–GeTe pseudo-binary line (GeSe1-xTex alloys). This alloy series bridges GeSe, characterized by a covalently bonded orthorhombic crystalline structure and ultra-low optical losses, and GeTe, a prototypical phase-change material whose rhombohedral crystalline phase is governed by metavalent bonding. Most GeSe1-xTex compositions exhibit a large refractive index contrast with limited absorption changes, resulting in FOM values up to 550 percent higher than GST225 and up to three times greater than GSST2241. Nitrogen-doped GeSe1-xTex thin films perform even better: N-doped GeSe0.5Te0.5 combines a FOM of 11.6 at 1550 nm, a large refractive index contrast, low optical losses, and a high crystallization temperature of about 345 °C. The material properties can be tailored by adjusting the Se/Te ratio and nitrogen content during deposition. As a bonus, all these alloys exhibit exceptionally high nonlinear Kerr coefficients and negligible two-photon absorption, outperforming many conventional nonlinear photonic materials and making them attractive for supercontinuum and frequency-comb generation.

Turning to devices, the review presents novel photonic designs for electrical PCM actuation. A key requirement for advanced photonic computing is the ability to encode multiple discrete phase levels, typically achieved through partial amorphization of the PCM layer, where intermediate refractive indices correspond to intermediate phase shifts. Conventional designs based on uniform heaters suffer from abrupt phase transitions because small variations in pulse parameters can produce disproportionately large phase shifts. To overcome this, the researchers propose a segmented heater architecture in which the heater width varies along the propagation direction, introducing a controlled thermal gradient so that different segments of the PCM experience distinct degrees of amorphization. When averaged across multiple segments, the cumulative effect is a smooth overall amorphization and a nearly continuous phase-shift response. This approach enables up to 164 distinguishable phase levels—greater than 7-bit resolution—with low insertion loss of approximately 0.6 dB in the worst case, while complying with standard foundry constraints (minimum heater width of 1 µm with incremental increases of 50 nm). The average power dissipation across the segmented heater is approximately 0.94 W, with programming pulse durations from 142 to 1015 ns, corresponding to an energy consumption ranging from 133 nJ to 955 nJ.

The researchers also present a hybrid-mode interferometer (HMI) that directly integrates phase-change modulation with modal interference in a single compact structure. The HMI exploits interference between hybridized transverse modes in a silicon waveguide integrated with a PCM layer at 1550 nm. By utilizing the vertical asymmetry of the structure, the waveguide is engineered to support hybridization between the fundamental TM mode and the first higher-order TE mode. In the crystalline state, the PCM-integrated waveguide length is selected to allow constructive interference, providing high transmittance with ultra-low insertion loss. In the amorphous state, nearly equal modal amplitudes arise from near-perfect hybridization, resulting in very low transmittance because the phase difference approaches destructive interference. This mechanism enables a high extinction ratio of about 14 dB within a compact footprint of roughly 24 µm length, with transmittance varying from 0.98 to 0.04—suitable for analog encoding and multi-bit storage with sub-microsecond switching speeds. Compared with conventional architectures, the HMI provides a good trade-off between compactness, multilevel encoding capability, and low insertion losses: MZI-based PCM phase shifters have large footprints (hundreds to thousands of square micrometers) because of input/output couplers and cross-talk constraints, while ring resonators, though compact, encode only a limited number of levels—for example, up to only 14 distinct optical levels demonstrated with a graphene-actuated Sb2Se3-based ring resonator.

Finally, the review presents experimental results for optically actuated GST225-based waveguides on silicon-on-insulator. GST225 patches integrated onto SOI waveguides were characterized under all-optical programming and readout conditions, with propagation losses of approximately 5 dB/µm at 1550 nm. A heterodyne interferometric setup—using a short 400 ps amorphization pulse followed 25 µs later by a longer, less intense recrystallization pulse, with a low-power 0.6 mW probe laser—monitored transmission and phase variations in real time. For a 1.5 µm-long GST225 patch, 400 ps amorphization pulses with an energy of approximately 100 pJ produced a transmission increase of about 60 percent and a phase-delay reduction of 55°. The write–erase sequence, using optimized pulse energies of 100 pJ and 7.4 nJ, was repeated over a 14-hour cycling test, providing a quantitative assessment of reversibility and endurance under repeated optical programming. The researchers conclude that the combination of devices based on electrical and optical actuation using different PCM compounds can provide a path toward achieving both static synaptic weighting (electrically) and dynamic synaptic reconfigurability, signal summation, and activation functions (optically)—the missing ingredient to enable next-generation computing systems where all the key functions can be addressed by either optical or electrical stimuli, depending on the exact required function.

Subject of Research: Physics

Article Title: Photonic devices based on phase-change materials for neuromorphic computing

Article References: Dwivedi, R., Pourny, C., Albanese, A., Yadav, A., Orobtchouk, R., Benane, G., Sawant, R., Tomelleri, M., Brulé, Y., Rogemont, A., Coillet, A., Charbonnier, B., Noé, P., Cluzel, B., & Pavanello, F. (2026). Photonic devices based on phase-change materials for neuromorphic computing. Frontiers in Photonics, 7, Article 1918762. https://doi.org/10.3389/fphot.2026.1918762

Image Credits: AI Generated

DOI: 10.3389/fphot.2026.1918762

Keywords: phase-change materials, photonics, neuromorphic computing, photonic computing, chalcogenides, optical memory, silicon photonics, Photonic, devices, based, phase-change, materials

The biodegradable polymer at the heart of the work is poly(butylene adipate-co-terephthalate), or PBAT, a flexible compostable plastic familiar from shopping bags and food packaging films. PBAT is cheap, tough and breaks down in the environment, which makes it an attractive candidate for a carrier scaffold that encapsulates a phase-change material. Yet, as the authors note, PBAT has been substantially underexplored in this role, largely because making it porous is surprisingly difficult. The two standard routes each carry a serious flaw. Phase inversion, in which a polymer solution is cast and the solvent is exchanged away, relies on toxic organic solvents that sit awkwardly with any claim to sustainability. Carbon dioxide foaming, meanwhile, tends to produce predominantly closed-cell pores, tiny sealed bubbles that a molten phase-change material cannot easily enter or be retained within.

The Chinese team’s solution borrows its logic from one of the oldest techniques in materials processing: hot-pressing. Instead of dissolving PBAT or blowing it into foam, they used a graphene oxide aerogel as both a dispersion medium and a carrier for PBAT powder particles. Graphene oxide, the oxidized flake form of graphene, naturally assembles into lightweight three-dimensional networks when dispersed in water and frozen or gelated. Into this porous carbon scaffold the researchers introduced PBAT powder, allowing the particles to distribute uniformly and aggregate throughout the aerogel interior to form a macroscopically stable PBAT/GO composite aerogel. The key trick came next: isothermal heating. Held at a temperature that softened but did not destroy the polymer, adjacent PBAT particles began to melt at their contact points and fuse together, a process the authors describe as melt-bridging, effectively welding the powder into a continuous porous skeleton in situ.

What makes the resulting pore architecture clever is that it is formed by two cooperating mechanisms. The three-dimensional graphene oxide network provides the macroscopic template, while the physical space occupied by ice crystals during the freezing step carves out additional channels. When the ice sublimes or melts away, it leaves behind an interconnected, open-pore structure, precisely the kind of plumbing that a liquid phase-change material needs. The graphene oxide is simultaneously reduced to reduced graphene oxide during the thermal treatment, yielding the final PBAT/rGO porous composites, labeled PG-x, where x denotes the compositional series. No toxic solvent is involved at any stage, and the process avoids the closed-cell trap that has limited foamed PBAT carriers.

With the scaffold in hand, the researchers loaded it with polyethylene glycol, or PEG, a workhorse organic phase-change material that stores and releases large amounts of latent heat near room temperature. Loading was accomplished by vacuum impregnation, in which the porous composite is evacuated and then flooded with molten PEG so that capillary forces draw the liquid deep into every interconnected channel. The resulting shape-stable composites, designated PGP-x, held an average actual PEG loading ratio that peaked at 70.04 weight percent, an impressively high fraction for a polymer-based support. At that loading the composite delivered a phase-change enthalpy of 110.37 joules per gram, meaning that each gram of material absorbs or releases more than a hundred joules of heat as PEG melts and solidifies.

Shape stability, the property that gives these composites their name, is where the numbers become genuinely striking. The researchers subjected the PGP-x samples to 100 consecutive thermal cycles of melting and freezing, a torture test that would quickly expose any weak scaffold. After 100 cycles, the leakage rate remained below 2 weight percent, indicating that the welded PBAT/rGO network, together with capillary confinement and possible interfacial interactions between PEG and the reduced graphene oxide walls, keeps the molten wax-like PEG locked in place. For applications such as building envelopes, solar thermal collectors, battery thermal management and waste-heat recovery, where a leaking composite would stain, corrode or short-circuit surrounding components, that kind of cycling durability is the difference between a laboratory curiosity and a deployable technology.

The graphene component contributes more than mechanical containment. Graphene oxide and its reduced form are strong broadband absorbers of solar radiation, converting absorbed photons into heat with high efficiency. Because the reduced graphene oxide sheets line the pore walls throughout the composite, sunlight penetrating the material is captured close to where the PEG is stored, so the photothermal conversion performance of the PGP-x composites was significantly enhanced relative to the neat phase-change material. In practical terms, this means the composites can be charged directly by sunlight: place them in the sun and the graphene framework heats up, melts the PEG, and the latent heat is banked for later release. This light-driven charging pathway opens the door to passive solar energy storage in walls, windows, textiles and off-grid devices without any pumps, heat exchangers or electrical input.

The choice of a biodegradable carrier deserves emphasis in an era when the materials community is scrutinizing the end-of-life footprint of every new composite. Most shape-stable phase-change composites reported to date rely on non-degradable supports such as expanded graphite, metal foams, polyurethane foams or MXene-polymer hybrids. A PBAT-based scaffold, by contrast, can in principle compost along with the polymer matrix once the storage material is recovered, aligning the composite with circular-economy principles. The authors argue that their solvent-free, hot-pressing-inspired preparation method offers novel insights for latent heat energy storage research precisely because it sidesteps the environmental liabilities of phase inversion while solving the pore-connectivity problem of CO2 foaming. The approach is also conceptually portable: any thermoplastic powder that melt-bridges under isothermal heating could, in principle, be welded inside a graphene oxide or other aerogel template by the same route.

There are, of course, questions that follow any such laboratory demonstration. The reported enthalpy of 110.37 joules per gram, while respectable, is below that of pure PEG, since the non-melting scaffold dilutes the active material, and further engineering would be needed to push energy density toward the levels demanded by grid-scale storage. Long-term behavior beyond 100 cycles, mechanical robustness under compression, and the cost of graphene oxide at scale all remain open engineering challenges. The work was supported by the National Natural Science Foundation of China and startup funding from the Guizhou Institute of Technology, and the authors report no conflicts of interest. Still, the demonstration that a humble compostable plastic can be thermally welded into a high-performance, sunlight-charging heat reservoir, using water, ice and heat as the only processing agents, is the kind of elegant simplification that tends to reshape a field.

If the broader promise holds, the implications extend well beyond thermal storage. The same in situ thermal welding strategy could produce open-porous PBAT structures for filtration membranes, oil-spill remediation monoliths, tissue engineering scaffolds and electromagnetic shielding foams, all areas where PBAT composites are already being explored but where solvent-free, interconnected porosity has been hard to achieve. For the energy transition, meanwhile, the study adds a compelling entry to the growing catalog of carbon-based porous supports for form-stable phase-change materials, one distinguished by its biodegradability and by the sheer simplicity of its fabrication. A plastic bag polymer, a graphene oxide aerogel and a hot plate may sound like an unlikely recipe for the future of heat storage, but the numbers, 70 percent loading, 110 joules per gram, and less than 2 percent leakage over a hundred melt-freeze cycles, make a persuasive case that sometimes the greenest route is also the simplest one.

Subject of Research: Biodegradable PBAT/reduced graphene oxide porous scaffolds for shape-stable composite phase-change thermal energy storage materials

Article Title: In situ thermal welding for constructing PBAT/rGO porous structures for shape-stable composite phase-change materials

Article References: Zhang, Y., Luo, D., Zhang, X., & Deng, Y. (2026). In situ thermal welding for constructing PBAT/rGO porous structures for shape-stable composite phase-change materials. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13861-y

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13861-y

Keywords: phase-change materials, PBAT, graphene oxide, thermal energy storage, polyethylene glycol, biodegradable polymers, aerogel, porous materials, photothermal conversion, shape-stable composites, thermal welding, latent heat

The sheer scale of the growth is remarkable. Publications in AI-driven biomimetics remained sparse through the 1990s, when only a handful of pioneering works laid the conceptual foundations. Interest began accelerating after 2000, but the real explosion came after 2016, driven by advances in machine learning, optimisation algorithms, and bio-inspired computing. The field peaked in 2021 with a surge of highly cited studies, and although publication volumes stabilised between 2022 and 2024, the authors interpret this as a sign of maturity rather than decline, with research efforts consolidating and new thematic areas emerging. Citation patterns showed peaks around 2015 and 2020, indicating that certain studies gained considerable academic influence and that researchers are increasingly building cumulatively on previous findings rather than working in isolation.

To construct this map, the team employed VOSviewer version 1.6.20, a widely used tool for constructing and visualising bibliometric networks. They combined citation analysis with content analysis, examining publication trends, co-authorship networks, and keyword co-occurrence patterns. The search query used Boolean operators to pair AI-related terms, including artificial intelligence, machine learning, neural networks, model predictive control, and evolutionary algorithms, with biomimetics-related stems such as biomimetic, biomimicry, bioinspired, and bio-inspired. Author keywords were cleaned using a thesaurus file to merge spelling variants and abbreviations, and only keywords appearing at least six times were included in the final co-occurrence network. Out of 17,552 unique keywords, 103 met this threshold, providing a statistically robust picture of the field’s conceptual structure.

The keyword analysis revealed a field organised around three dominant clusters. The first and most prominent centres on AI in biomimetic robotics, where terms such as bio-inspired robotics, artificial neural networks, reinforcement learning, and swarm intelligence form dense, strongly connected associations. The second cluster revolves around optimisation and computational intelligence, featuring evolutionary algorithms, genetic algorithms, particle swarm optimisation, and deep learning. The third, spanning neuromorphic computing, synaptic learning, and memristive devices, bridges AI, neuroscience, and biomimicry, reflecting the rise of brain-inspired computing models. Artificial neural networks emerged as the single most connected keyword, with 914 occurrences and a total link strength of 954, followed by machine learning with 711 occurrences and a link strength of 843. Deep learning showed a notably recent average publication year of 2021.47, confirming its rapid ascent within the field.

Then comes the surprise. Energy-related terms barely register on the map. The keyword energy ranked just 41st, with only 49 occurrences and a total link strength of 82, while maximum power point tracking, a cornerstone of renewable energy systems, ranked 98th with a mere 14 occurrences. In the citation analysis by research field, Energy accounted for just 119 citations, compared with 2,687 for Engineering and 1,602 for Science. The overlay visualisation, in which colours represent average publication years, confirmed that energy terms sit at the periphery of the network, weakly linked to the central AI and optimisation clusters. For a field that promises sustainable, nature-inspired solutions, the near-absence of energy applications represents a striking disconnect between potential and practice.

The geographic distribution of research output adds another layer to the story. China leads with 2,136 publications, followed by India with 1,443 and the United States with 1,402. Yet when it comes to citation impact, the United States dominates with 57,016 total citations, far ahead of China’s 47,945, suggesting differences in the influence and visibility of research contributions. European nations, including the United Kingdom, Spain, Italy, Germany, and France, feature prominently, reflecting robust academic infrastructure supporting biomimetic research. Emerging economies such as Brazil, Iran, and Saudi Arabia are steadily increasing their contributions, and the collaboration network analysis revealed strong interconnections between major hubs, with newer players establishing growing ties to established research centres. On the individual level, Simon X. Yang of the University of Guelph leads the field with 38 relevant publications and an h-index of 56, while researchers from Mexico’s Tijuana Institute of Technology and Singapore’s National University also rank among the most prolific contributors.

The study also examined where this research is published and who funds the institutional engines behind it. Journal papers dominate the output, followed by conference papers, while book-length treatments remain rare, which the authors identify as a gap in long-form synthesis. Advances in Intelligent Systems and Computing leads by publication volume with 276 papers, but Advanced Materials tops citation impact with 7,888 citations, followed by IEEE Transactions on Systems, Man, and Cybernetics with 7,201. Specialised venues such as Bioinspiration and Biomimetics and Neurocomputing play a crucial bridging role between computational intelligence and bio-inspired engineering. Institutionally, Cairo University’s Faculty of Computers and Information ranks first by citations with 1,735 from just 12 documents, while the University of Chinese Academy of Sciences is the most productive with 26 publications, underscoring that computational intelligence and optimisation groups, rather than energy departments, currently drive the field.

Beneath the statistics lies a compelling technical narrative about what AI actually does for biomimetic design. Machine learning models trained on biological data can predict material properties and suggest optimal compositions, as demonstrated by AI-driven simulations of hierarchical structures found in nacre and spider silk that have informed ultra-lightweight, high-strength composites. Machine-learning-assisted design of nacre-inspired composites and gradient architectures has improved strength-toughness trade-offs, while AI-powered optimisation has refined bio-inspired surfaces such as lotus-leaf-inspired hydrophobic coatings and gecko-inspired adhesives. In robotics, neural networks, reinforcement learning, and computer vision enable bio-inspired machines to learn from their environments, adjust their movements dynamically, and navigate unpredictable terrain, with swarm intelligence coordinating collaborative robotic systems. In medicine, neural networks trained on biological datasets advance diagnostics, prosthetic design, and bio-fabrication techniques such as 3D bioprinting of tissues and organs.

So why does energy lag so far behind? The authors identify concrete technical shortfalls across three subareas. In thermal energy storage with phase change materials, AI has been used for performance prediction and parameter inference, but end-to-end, bio-inspired AI pipelines for tank geometry design, PCM selection, encapsulation, and degradation-aware control remain scarce, with few studies translating natural thermoregulation strategies into AI control policies at system scale. In solar energy, bio-inspired micro and nanostructures for light trapping and anti-reflection exist, but demonstrations at module scale incorporating durability, manufacturability, and cost in multi-objective optimisation are limited. In wind energy, AI-guided morphing surfaces modelled on bird and whale fin analogues exist primarily as prototypes or simulations, with few field-validated, AI-in-the-loop controllers that co-optimise efficiency, loads, and noise under real turbulence spectra. The pattern is consistent: promising concepts, but few validated, scalable deployments.

The message for the research community is clear. The convergence of AI and biomimetics has already transformed robotics, neuromorphic computing, and optimisation, but its application to energy systems, biomimetic materials, sensory perception mimicking echolocation or insect vision, and adaptive control remains an emerging frontier. The authors argue that closing this gap will require deliberate cross-disciplinary collaboration between AI scientists, energy engineers, and biomimetic researchers, spanning thermal energy storage, solar and wind technologies, energy harvesting, and smart grid management. Given that bio-inspired algorithms can optimise energy consumption and that AI-driven predictive models can enhance the adaptability of renewable energy systems, the untapped potential is substantial. If the trajectory of the past decade is any guide, the energy sector may be the next arena where nature’s blueprint, decoded by machines, delivers its most consequential innovations yet.

Subject of Research: Bibliometric mapping of artificial intelligence applications in biomimetic and bio-inspired technologies

Article Title: Bibliometrics in artificial intelligence in biomimetic and bio-inspired technologies: mapping the research landscape and identifying knowledge gaps

Article References: Mehraj, N., Mateu, C., Borri, E., Castro-Gomes, J., & Cabeza, L. F. (2026). Bibliometrics in artificial intelligence in biomimetic and bio-inspired technologies: mapping the research landscape and identifying knowledge gaps. Heliyon, 12(15), Article e45560. https://doi.org/10.1016/j.heliyon.2026.e45560

Image Credits: AI Generated

DOI: 10.1016/j.heliyon.2026.e45560

Keywords: artificial intelligence, biomimetics, machine learning, bibliometrics, bio-inspired robotics, neuromorphic computing, thermal energy storage, renewable energy, swarm intelligence, phase change materials, keyword co-occurrence, research trends

Phase change materials are deceptively simple in concept. When a paraffin wax, a salt hydrate, or a polyethylene glycol melts, it absorbs a large quantity of latent heat at a nearly constant temperature; when it solidifies again, that heat is released. This makes PCMs ideal for banking thermal energy and for passively regulating temperature in buildings, electronics, and batteries. Yet the classic formulations suffer from three chronic weaknesses. First, once molten, they leak, which means they must be contained or encapsulated before they can be deployed. Second, most organic PCMs conduct heat poorly, so charging and discharging the store is slow and temperature gradients build up inside the material. Third, conventional PCMs merely store heat; they do not convert other forms of energy into it, limiting their usefulness in systems that need to harvest sunlight or electricity directly.

MXenes, first reported in 2011 when researchers exfoliated the layered ceramic Ti3AlC2 into two-dimensional titanium carbide sheets, have rapidly become one of the most versatile nanomaterial platforms in materials science. These transition metal carbides and nitrides carry a chemically tunable surface terminated with functional groups, and they combine metallic electrical conductivity with strong in-plane thermal transport. The review emphasizes that this combination is precisely what leaky, sluggish PCMs need. Dispersed or structured within a phase change matrix, MXene nanosheets act simultaneously as a thermal bridge that accelerates heat distribution, an absorbent scaffold that locks the molten PCM in place by capillary forces and surface interactions, and in many designs as the actual energy converter that turns sunlight or electricity into stored heat.

The authors devote considerable attention to how these composites are made, beginning with MXene synthesis itself. The dominant route remains selective etching of the aluminum layers from MAX phase precursors, typically using hydrofluoric acid or gentler fluoride salt mixtures such as hydrochloric acid combined with lithium fluoride, followed by delamination into single-layer sheets. Newer protocols, including electrochemical etching, dry selective extraction guided by computation, and even ultrafast laser synthesis of MAX phases, are expanding the toolkit and reducing the environmental burden of the fluoride chemistry. The review notes that etching conditions directly control the surface terminations, defect density, and flake size of the resulting MXene, which in turn govern how well the nanosheets disperse in a PCM, how strongly they bind the melt, and how efficiently they conduct heat through the composite.

Encapsulation strategies form the second pillar of the review. The simplest approach is the form-stable composite, in which a porous MXene aerogel or hydrogel-derived framework is infiltrated with molten paraffin or polyethylene glycol, producing a monolith that holds its shape even above the melting point. Binderless MXene aerogels assembled without polymeric binders have achieved ultrahigh energy storage densities alongside exceptional electromagnetic interference shielding, a bonus property that stems from the electrical conductivity of the percolating nanosheet network. Hybrid frameworks that pair MXene with graphene or with copper nanowires exploit synergistic conduction pathways, while polymer partners such as polyvinyl alcohol, gelatin, cellulose nanofibers, and polyurethane add mechanical flexibility, producing composite films that can be bent, wrapped around pipes, or integrated into fabrics. Microencapsulation, in which PCM droplets are shelled in silica or polymer with MXene incorporated into the shell or coating, offers another route to leakage-proof, supercooling-suppressed particles suitable for slurries and coatings.

Solar photothermal conversion is where MXene composites deliver their most eye-catching performance. Broad absorption across the solar spectrum, combined with efficient conversion of absorbed photons into heat, allows MXene-loaded PCMs to charge rapidly under illumination. Paraffin infiltrated into Ti3C2Tx MXene and gelatin aerogels, MXene aerogel monoliths, diatomite ceramics coated with MXene, kapok fibers modified with the nanosheets, and composites decorated with gold nanorods or nano copper have all demonstrated high solar-thermal conversion efficiencies and strong shape stability. The review highlights designs that pair MXene with polydopamine for synergistic photothermal enhancement, with biochar from sorghum straw for sustainable scaffolds, and with liquid metal gallium modified on blackbody-inspired principles, extending the concept to interfacial evaporation and desalination where stored heat drives water purification after sunset.

Electrothermal applications form a complementary frontier. Because MXenes conduct electricity, a composite PCM can be charged simply by passing current through it, converting electrical energy into latent heat with near-total efficiency. Flexible films based on polyethylene glycol with two-dimensional MXene, aramid nanofiber composites, cellulose nanofiber materials, and sandwich-structured MXene and polyvinyl alcohol systems with barium sulfate have demonstrated dual-mode solar and electrothermal charging. Such films are candidates for wearable thermal management, defrosting surfaces, and electrically rechargeable heat packs, and the review notes that molecular dynamics studies of lauric acid in polylactic acid and MXene matrices are now providing atomistic insight into how the filler alters crystallization and heat transport.

Perhaps the most consequential application is thermal safety in batteries and electronics. Lithium-ion cells can enter catastrophic thermal runaway when heat accumulates faster than it is removed, and the review cites extensive work on MXene-based composite PCMs for passive battery cooling. Composites pairing MXene with carbon nanotubes, expanded graphite, hexagonal boron nitride nanosheets for electrical insulation, or VO2 for thermally triggered tunable conductivity can absorb heat spikes during fast charging or high discharge, delay the onset of runaway, and in flame-retardant formulations actively suppress fire propagation. Similar composites protect power electronics and LED systems, and some add electromagnetic interference shielding and even radiation protection, turning a simple heat sink into a multifunctional protective layer.

The review closes with a candid assessment of obstacles and a striking glimpse of the future. MXenes are vulnerable to oxidative degradation, which erodes their conductivity over time, and surface and edge passivation strategies are being developed to extend operational lifetimes. Large-scale, low-cost synthesis remains a hurdle, as does the long-term cycling stability of composites exposed to repeated melting. Yet the authors see these materials converging toward integrated platforms that convert, store, and manage energy in a single component: fabrics that harvest sunlight by day, warm the wearer at night, and hide the wearer’s infrared signature; battery packs that cool themselves and shield electronics; and building panels that smooth the intermittency of renewable power. Infrared camouflage, achieved by tuning emissivity and buffering surface temperature with phase change layers, illustrates how far the concept has traveled from simple heat storage. For a field racing to decarbonize, MXene-based composite PCMs, the review concludes, offer a rare combination of high latent heat, fast charging, and multifunctional intelligence that could define the next generation of thermal energy technologies.

Subject of Research: MXene-based composite phase change materials for thermal energy storage and management

Article Title: Review: MXene-based composite phase change materials for preparation, encapsulation, and thermal management

Article References: Wu, Y., Huang, Y., & Li, L. (2026). Review: MXene-based composite phase change materials for preparation, encapsulation, and thermal management. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13844-z

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13844-z

Keywords: MXene, phase change materials, thermal energy storage, encapsulation, photothermal conversion, electrothermal conversion, battery thermal management, infrared camouflage, two-dimensional materials, thermal conductivity, aerogels, renewable energy