The research team, led by Jinrong Cao of the Geological Carbon Dioxide Storage Technology Research Association and the Research Institute of Innovative Technology for the Earth in Japan, combined three observational streams in a single experiment: distributed fiber-optic strain sensing, time-lapse X-ray computed tomography, and coupled numerical modeling of two-phase flow and poroelastic deformation. Their specimen was a cylindrical tuffaceous sandstone core, 34.83 millimeters in diameter and 179.50 millimeters long, drilled from the Sarukawa oil field in Oga, Akita Prefecture, an area selected for a Japanese advanced carbon storage program targeted to begin operations by 2030. The rock had a porosity of 25.06 percent and an intrinsic permeability of 5.41 millidarcys, with a mineral framework dominated by the zeolite clinoptilolite at roughly 63 percent, alongside quartz, albite, anorthite, and heulandite.

The sensing element was a single-mode silica fiber bonded to the core surface with epoxy at an optimized wrap angle of 80 degrees relative to the core axis. This helical geometry converts one continuous fiber into a dense array of quasi-independent strain sensors, resolving circumferential, or hoop, strain at one-centimeter spatial resolution along the full specimen length. The interrogator, a Neubrex 7020 unit, works by measuring Rayleigh frequency shifts in backscattered laser light using a tunable wavelength coherent optical time-domain reflectometer. Because strain and temperature both shift the Rayleigh spectrum, the team held the experiment at a stable 40 degrees Celsius and applied a calibrated strain coefficient of minus 0.153 gigahertz per microstrain, yielding a strain resolution of about half a microstrain for comparable measurements, far finer than the tens to roughly one hundred microstrains observed during injection.

Before introducing carbon dioxide, the researchers ran a single-phase water flow test to pin down permeability and validate their poroelastic model. When upstream pressure reached 10.5 megapascals, circumferential strain near the inlet jumped to approximately 75 microstrains within a single sampling interval of 36 seconds or less, while the downstream end of the core registered only a few microstrains. Numerical simulations showed that the sub-second initial response could not be resolved experimentally, but by roughly half a second to one second the simulated strain gradient matched the first measured profile, and a steady inlet-to-outlet strain gradient established itself within about one second. This close agreement between measurement and model confirmed that, in fully water-saturated rock, deformation is governed by pore water pressure gradients acting through Biot-style poroelastic coupling.

The main event was the supercritical carbon dioxide flood. Time-lapse CT scans, taken at 60 seconds per volume using an iodide-rich contrast solution to sharpen fluid-rock contrast, tracked the drainage process in detail. During the first 1.6 minutes, corresponding to 0.036 injected pore volumes, carbon dioxide accumulated mainly near the inlet. By 2.67 minutes the saturation field had become spatially nonuniform, reflecting variability in pore accessibility and capillary entry conditions across the zeolite-rich framework. At 4.27 minutes the front reached the specimen midpoint, and breakthrough occurred at 8.0 minutes, when average carbon dioxide saturation hit 19.4 percent. Differential pressure during drainage held steady between 0.45 and 0.48 megapascals at a flow rate near one milliliter per minute.

The striking result was how differently the strain field evolved from the saturation field. At the onset of injection, a pronounced strain gradient appeared immediately: strain near the inlet climbed to roughly 80 microstrains, while even the outlet showed a small but detectable response. The strain front was far more spatially diffuse than the comparatively sharp saturation front imaged by CT. By breakthrough, strain had reached about 100 microstrains near the inlet and 20 microstrains near the outlet. Most tellingly, at a position 0.09 meters from the inlet, a distinct strain increase appeared near the very start of injection, while local carbon dioxide saturation remained at zero for the first four minutes. The delay between strain onset and saturation onset grew with distance from the inlet, exactly the pattern expected if pressure disturbances propagate through the connected aqueous phase faster than the capillary-controlled gas front advances.

The coupled numerical model, a two-dimensional axisymmetric finite-element representation of the full specimen, provided the physics-based bridge between the observable strain and the unmeasured internal pressure. The team calibrated two-phase flow parameters exclusively against the CT-derived saturation profiles, then compared the predicted strain against the fiber measurements as an independent test. Simulated pore gas and pore water pressures evolved concurrently but with different spatial patterns, related through capillary pressure, and the modeled strain reproduced both the magnitude and the timing of the measured response. Because the sandstone’s apparent drained bulk modulus of roughly one to two gigapascals makes it relatively compliant, a given pressure perturbation produces a large, measurable strain. The authors are careful to stress that the fiber does not measure pressure directly; the strain signal is a model-constrained poroelastic proxy for the evolving pressure footprint, not a standalone pressure gauge.

The engineering implications reach well beyond the laboratory. Operational surveillance of storage sites typically relies on wellhead and bottomhole pressure, flow rates, sparse downhole gauges, and episodic plume imaging, none of which uniquely constrains the internal pressure field. Distributed strain sensing adds a spatially continuous constraint that can be folded into coupled flow and geomechanical models, helping to characterize uncertain formation properties and to evaluate deformation relevant to reservoir, caprock, and wellbore integrity. Field deployments already hint at feasibility: distributed fiber sensing has been demonstrated under field-scale injection conditions at the CO2CRC Otway site in Australia, a pumping test at Mobara in Japan captured pressure-related reservoir deformation, and behind-casing water-injection measurements show that injection-induced strain is detectable through a casing-cement-formation system.

The authors are equally candid about the limitations that separate their benchtop result from routine field practice. The adhesive layer bonding the fiber to the core was not independently calibrated, so perfect strain transfer was assumed. Field fibers are usually installed axially behind casing, where recorded amplitude depends on cable orientation, completion design, cement properties, gauge length, and strain-transfer efficiency, and axial strain is not generally equivalent to the hoop strain measured here. Stiffer formations or rocks with a lower Biot-Willis coefficient would produce smaller strains that may fall below detection thresholds, meaning an absent strain signal cannot be read as absent pressure communication. The homogeneous axisymmetric model also cannot capture localized effects of bedding, fractures, or anisotropic permeability, and longer-term chemical interactions between carbon dioxide, brine, and reactive minerals may gradually alter rock stiffness and fracture behavior.

Even with those caveats, the study delivers a compelling proof of concept: the mechanical consequences of injection arrive before the plume does, and a helically wound strand of glass can watch them happen. Future priorities include experiments on rocks with contrasting stiffness and capillary behavior, direct internal pressure measurements, three-dimensional models that explicitly represent the helical fiber geometry, and field studies that integrate distributed strain with pressure gauges, time-lapse geophysics, distributed acoustic and temperature sensing, and surface deformation observations. As global net-zero pathways call for roughly ten gigatons of carbon dioxide storage per year by 2050, tools that convert invisible pressure transients into measurable, interpretable strain signals could become an essential part of the monitoring toolkit, giving operators and regulators earlier and more defensible warnings about where the subsurface is being mechanically stressed.

Subject of Research: Distributed fiber-optic sensing of poroelastic strain precursors during supercritical CO2 core flooding in sandstone

Article Title: Poroelastic strain precursors during laboratory carbon dioxide core flooding revealed by helically bonded fiber sensing

Article References: Cao, J., Park, H., Xue, Z., Nakajima, T., Amer, R., & Ouchi, W. (2026). Poroelastic strain precursors during laboratory carbon dioxide core flooding revealed by helically bonded fiber sensing. Communications Engineering, 5(1), Article 164. https://doi.org/10.1038/s44172-026-00783-5

Image Credits: AI Generated

DOI: 10.1038/s44172-026-00783-5

Keywords: carbon capture and storage, distributed fiber-optic sensing, poroelasticity, CO2 core flooding, X-ray computed tomography, pore pressure, geomechanics, sandstone, capillary pressure, geological storage, strain sensing, two-phase flow

The stakes are higher than they might first appear. Copper anodes cast in these molds move directly into electrorefining cells, where they dissolve into a sulfuric acid electrolyte and re-deposit as ultra-pure cathode copper. When barium sulfate particles cling to the anode surface, they act as non-conductive obstacles that shrink the effective electrochemically active area, raising cell voltage and slowing copper dissolution. Worse, because barium sulfate is almost completely insoluble in the acidic electrolyte, detached particles sink to the cell floor and inflate the volume of anode slime, the residue that must be processed to recover gold, silver, and platinum-group metals. Every kilogram of inert barium sulfate in that slime dilutes its precious metal content, driving up the cost and complexity of recovery circuits.

The research team, led by Mahdi Jafari Mohammadabadi of Shahid Bahonar University of Kerman in collaboration with colleagues at the Sarcheshmeh complex, began with a forensic question: why does a coating used for decades fail so consistently? The answer lay in the mineralogy of the local barite ore. X-ray fluorescence analysis of the commercial coating revealed 1.8 weight percent iron oxide and a loss-on-ignition of 0.9 percent, signatures of incomplete beneficiation and trapped volatile components. During casting, those iron-bearing minerals partially decompose or oxidize, forming reactive oxides that chemically bond with the solidifying copper surface. Meanwhile, moisture and organic matter trapped in the coating decompose violently on contact with the 1200-degree-Celsius melt, blasting voids into the coating that let molten copper penetrate between coarse, angular barite grains and mechanically lock itself in place.

Microscopy sealed the case. Scanning electron microscopy with energy-dispersive X-ray spectroscopy showed that adhered patches on contaminated anodes were enriched in barium, sulfur, and iron, while the clean copper matrix contained none of these elements above detection limits. The problem, in other words, was not operator error or an inherent flaw in barium sulfate coatings, but the impurity-laden, coarse-grained character of the specific commercial product in use. That diagnosis opened the door to a redesign rather than a replacement of the entire coating philosophy.

The team’s alternative began with materials most smelters would discard. Low-grade barite waste, recycled coke dust from the Zarand Coke Plant, and weak acid effluent containing 6.2 percent sulfuric acid from the smelter’s own gas-cleaning plant were combined in a closed-loop synthesis. The barite was first ground to 74 micrometers and roasted with coke at 1200 degrees Celsius, where carbothermal reduction converted barium sulfate to soluble barium sulfide with 99.1 percent conversion efficiency. Water leaching dissolved the barium, and the addition of the sulfuric acid effluent precipitated it back out as barium sulfate, this time in a form of exceptional purity: more than 99.95 weight percent, with iron oxide reduced by over 99 percent to below 0.01 percent and volatile content nearly eliminated. The overall recovery yield reached 96.5 percent, and the only significant byproduct was a silica-alumina residue that the researchers put to use rather than discarding.

Purity was only half the story. Seeded precipitation, using a small addition of sub-micron barium sulfate as a nucleating agent, produced a powder with a narrow, unimodal particle size distribution centered on a median diameter of roughly 8 micrometers. The commercial coating, by contrast, showed a broad distribution with substantial fractions exceeding 40 micrometers and a porous, interconnected network of voids. That difference matters because of a simple piece of physics: according to the Young-Laplace equation, the capillary pressure that resists liquid penetration into a pore scales inversely with pore radius. The researchers calculated that the coarse commercial coating offers only about 50.7 kilopascals of capillary resistance, easily overcome by molten copper, while the refined synthetic powder raises the barrier to roughly 253 kilopascals, effectively sealing the pores against infiltration and the mechanical interlocking that follows.

The final ingredient was a deliberate act of self-destruction. The silica-alumina residue recovered from the acid leaching stage was blended back into the purified barium sulfate at controlled levels, creating an engineered ternary system of roughly 95 percent barium sulfate, 2.9 percent silica, and 2.1 percent alumina. The alumina lends refractory strength, keeping the coating intact against thermal erosion during pouring. The silica does something more subtle: differential scanning calorimetry revealed a distinct endothermic peak at 573 degrees Celsius, the well-known alpha-to-beta polymorphic transformation of crystalline quartz, which involves an abrupt volume change. As the casting cools through this temperature, the silica grains contract sharply, generating localized micro-stresses and microcracks within the dense coating matrix. Those stresses actively weaken the bond between coating and anode, promoting spontaneous release precisely when it is needed, after the copper has solidified.

Laboratory casting trials put the concept to the test with five independent replicates under identical thermal conditions, using molten copper at approximately 1200 degrees Celsius poured into preheated molds carrying a 300-micrometer coating layer. The results were striking. Copper cast against the commercial barium sulfate coating showed extensive adhered residues, with an average adhesive mass transfer of 2.45 grams per trial. Copper cast against the engineered coating released spontaneously in every single experiment, leaving smooth, residue-free surfaces with an average mass transfer of just 0.018 grams, a reduction of more than 99 percent that the team reports as statistically significant. Electron microscopy confirmed no detectable transfer of barium or sulfur to the copper, with residual concentrations below 100 parts per million. Benchmarked against graphite-based washes, which risk carbon pickup, and zircon coatings, which carry high raw material costs, the waste-derived formulation outperformed both on release performance while costing less to produce.

The economic and environmental logic is as compelling as the metallurgy. Because the synthesis consumes barite tailings, recycled coke, and industrial acid effluent that would otherwise require disposal, the researchers estimate a roughly 38 percent reduction in raw material acquisition costs relative to commercial formulations, alongside reduced hazardous waste handling. The approach exemplifies a circular metallurgical paradigm in which a smelter’s waste streams become feedstock for its own consumables. The authors are careful to note that the results, while dramatic, were obtained under controlled laboratory conditions; scaling up will require industrial trials covering automated slurry preparation, spray application, and the continuous thermal cycling of full production wheels. Still, the central finding stands as a genuine conceptual shift: barium sulfate coating adhesion, long treated as an unavoidable cost of anode casting, is revealed to be a controllable outcome of composition and microstructure. By purifying the mineral, refining its pores, and building in a quartz-powered debonding mechanism, the researchers turned a century-old nuisance into a demonstration that sometimes the best way to fix an industrial process is to feed it its own garbage.

Subject of Research: Development of a waste-derived barium sulfate mold coating to eliminate adhesion in copper anode casting

Article Title: Analysis of barite Mold coating adhesion and development of negligible-adhesion waste-derived alternatives in copper anode casting

Article References: Jafari Mohammadabadi, M., Nemat, S., Khayati, G. R., Hajmohammadi, H., & Khezripour, M. (2026). Analysis of barite Mold coating adhesion and development of negligible-adhesion waste-derived alternatives in copper anode casting. Results in Chemistry, 31, Article 103932. https://doi.org/10.1016/j.rechem.2026.103932

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103932

Keywords: copper anode casting, barium sulfate, mold coating, electrorefining, barite, waste valorization, capillary pressure, thermal debonding, anode slime, circular metallurgy, Sarcheshmeh Copper Complex, silica polymorphic transformation

The review, led by Arash Ghaitaranpour of Ferdowsi University of Mashhad together with Mohsen Esmaiili, Zoleykha Fahimi vajargahi, and Michael O. Ngadi, reexamines frying technologies through the lens of three distinct oil fractions first described in classic work on French fries. Surface oil, or SO, is the film that clings to the outside of a fried product without penetrating its microstructure. Penetrated surface oil, or PSO, is oil that begins on the surface but is later sucked into the porous crust. Structural oil, or STO, is oil that migrates into the food’s interior during frying itself. By separating total oil content into these components, the authors reveal that seemingly contradictory results across decades of frying research begin to make sense: different technologies reduce oil uptake by intervening at entirely different stages of the process.

The physics of oil absorption is more subtle than most people assume. During frying, two countercurrent mass transfer processes unfold simultaneously. Water and water-soluble compounds migrate from the food’s moist core toward the surface, where they evaporate violently, while heat flows inward through convection and conduction. The escaping vapor generates positive pressure inside the food, and this outward flow actually resists oil penetration during most of the frying period. As a result, structural oil typically represents only a small share of total oil content. The crucial event happens after the food leaves the fryer. As the product cools below 100 degrees Celsius, water vapor inside the pores condenses, internal pressure drops sharply, and the resulting vacuum effect draws surface oil deep into the crust. Studies consistently show that more oil is absorbed during cooling than during frying itself, making the cooling stage the dominant target for oil reduction strategies.

Capillary forces add a second layer of complexity. The crust of a fried product is far more porous than its core; in French fries, the crust can be roughly six times more porous. Oil movement through these microscopic channels is governed by capillary pressure, which depends on pore radius, the contact angle between oil and the food surface, and oil surface tension. Smaller pores generate higher capillary pressures and thus greater oil uptake, and degraded frying oil, thickened by polymerization products and enriched with surface-active compounds formed during oxidation and hydrolysis, adheres more stubbornly to food surfaces. These findings help explain why oil quality, not just oil quantity, shapes the nutritional outcome of frying.

Viewed through this fraction-specific framework, each frying technology reveals a distinct mechanism of action. In conventional deep-fat frying, most absorbed oil ends up as penetrated surface oil drawn in during cooling. Pressure frying, widely used in commercial food service for meat and poultry, shortens frying time and improves moisture retention, but the review highlights an underappreciated factor: the pressure-release stage. When pressure is broken, vapor and liquids escape from the product, blocking oil entry and potentially expelling some oil already absorbed. Higher applied pressures consistently produce lower total oil content, suggesting that the pressure cycle itself, not merely faster cooking, drives the reduction.

Vacuum frying, performed at reduced pressure and correspondingly lower temperatures, preserves heat-sensitive nutrients and slows oil degradation. Yet its oil-saving benefit depends critically on how the vacuum is broken. When pressure returns to atmospheric levels, condensing vapor can pull oil inward; however, a rapid vacuum-breaking rate compresses the product, shrinking the internal space available for oil. The relationship between vacuum-breaking rate and oil absorption is roughly linear and inverse, meaning that fast decompression can substantially cut total oil content. The authors stress that vacuum breaking should be judged by processing conditions rather than labeled universally beneficial or harmful. Combined with centrifugal deoiling immediately after frying, careful pressure management allows vacuum-fried products to achieve markedly lower fat levels.

Hot-air frying, the technology behind the wildly popular domestic air fryer, operates on a fundamentally different principle. Because only a small amount of oil is sprayed onto the food rather than immersing it in a bath, little surface oil exists after frying, leaving almost nothing for capillary suction to draw in during cooling. The review’s fraction-based analysis shows that post-frying oil uptake in hot-air frying is effectively negligible; the lower total oil content stems from limited oil availability, not from altered cooling physics. Oil penetration during frying follows a latent phase, an acceleration phase in which most crust moisture evaporates, and a declining phase, but the absence of a substantial surface oil reservoir distinguishes this method from all pressure-based approaches.

Microwave frying presents the most inconsistent evidence of the technologies examined. Volumetric heating, generated by dipole rotation of water molecules and polar constituents, produces rapid internal steam generation and structural channels that can either restrain oil entry or create pathways for deeper penetration. Some studies report lower oil uptake at high microwave power, where fast water escape opposes absorption; others observe increased absorption from structural damage and uneven heating. Notably, microwave-fried products cooled at room temperature showed little post-frying oil change, and total oil content actually decreased when products were kept in a hot microwave cavity, apparently because reduced oil viscosity allowed surface oil to drain away. Infrared frying, by contrast, forms a smooth, hard crust quickly in starchy foods, reducing surface oil adhesion, though early crust formation can later crack and admit more penetrated surface oil during cooling. The authors caution that quantitative fraction data for infrared frying remain scarce.

The most novel technology reviewed is G-frying, in which centrifugal force is applied during or immediately after frying. Rotating the fryer basket strips vapor bubbles from the food surface, enhancing heat transfer and moisture loss, and then physically flings surface oil off the product before the vacuum effect can pull it inside. Because surface oil constitutes the largest share of total oil content in conventional frying, actively removing it represents a uniquely direct intervention. Oil removal efficiency depends on product orientation and structure, with vertically positioned samples draining better, while centrifugation speed and cooling time show surprisingly limited effects. Preliminary studies suggest G-fried products exhibit reduced oil uptake, improved texture, and reduced oil oxidation thanks to shorter heating exposure, though industrial validation is still limited.

The broader message of the review is methodological as much as technological. Because each frying technology alters a different stage of oil migration, comparing methods solely on final total oil content obscures the mechanisms that actually matter and renders much of the existing literature difficult to reconcile. The authors call for standardized fraction-specific analytical methods, real-time oil tracking, and industrial-scale validation, particularly for emerging approaches like G-frying and infrared frying. For food scientists and manufacturers, the implication is clear: designing healthier fried products requires not just less oil, but a precise understanding of which oil fraction to target, and when. For consumers watching the air fryer revolution reshape home cooking, the science now explains why it works, and hints at how the next generation of fryers could deliver the same crunch with even less fat.

Subject of Research: Fraction-specific oil absorption mechanisms in conventional and emerging food frying technologies

Article Title: From Deep‐Fat Frying to G‐Frying: Exploring Absorption Dynamics of Oil Fractions in Fried Foods

Article References: Ghaitaranpour, A., Esmaiili, M., vajargahi, Z. F., & Ngadi, M. O. (2026). From Deep‐Fat Frying to G‐Frying: Exploring Absorption Dynamics of Oil Fractions in Fried Foods. Food Science & Nutrition, 14(9), Article e72391. https://doi.org/10.1002/fsn3.72391

Image Credits: AI Generated

DOI: 10.1002/fsn3.72391

Keywords: deep-fat frying, oil absorption, surface oil, penetrated surface oil, structural oil, vacuum frying, air frying, microwave frying, G-frying, capillary pressure, vacuum effect, fried food health