According to the study abstract, the experimental films were examined by nanoindentation to assess hardness. Chromium was added in solid solution to strengthen the lattice, while yttrium was observed to enrich the examined grain boundaries. The researchers systematically varied the alloying-element contents with grain size kept constant, allowing them to investigate how grain-interior and grain-boundary chemistry jointly affected mechanical response.

Chromium additions produced solid-solution strengthening, but the abstract reports that this effect saturated at higher concentrations as grain-boundary-dominated deformation processes emerged. Indentation pileups containing slip steps and grain rotation provided evidence for those processes. Increasing yttrium concentration strengthened the grain boundaries by pinning dislocations and suppressing dislocation emission, grain-boundary sliding and grain rotation. The authors associated a weakened chromium contribution at higher yttrium concentrations with a reduced dislocation-bowing distance caused by dopant pinning.

The findings are based on the published abstract; the supplied source does not provide the full article, so the report cannot assess the complete methods, underlying measurements or uncertainties. Within the stated scope of nanocrystalline Ni-Cr-Y sputtered films, the results indicate that controlling both grain and grain-boundary chemistry can influence deformation mechanisms and increase hardness. The authors present this tuning approach as a possible strategy for strengthening nanocrystalline metals, but the reported evidence concerns hardness measured by nanoindentation rather than a broader range of structural or engineering performance tests.

Subject of Research: Effects of chromium and yttrium doping on hardness and deformation mechanisms in nanocrystalline Ni-Cr-Y films

Article Title: Synergistic doping of the grain interior and grain boundary alters deformation mechanisms and enables extreme strength in nanocrystalline Ni-Cr-Y alloys

Article References: Liu, Y., Trelewicz, J. R., & Rupert, T. J. (2026). Synergistic doping of the grain interior and grain boundary alters deformation mechanisms and enables extreme strength in nanocrystalline Ni-Cr-Y alloys. Journal of Materials Science, 61(43), 34103-34123. https://doi.org/10.1007/s10853-026-13753-1

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13753-1

Keywords: nanocrystalline alloys, nickel-chromium-yttrium, grain boundaries, solid-solution strengthening, nanoindentation, hardness, yttrium segregation, chromium doping, deformation mechanisms, materials science, Synergistic, doping

The results identify promising design criteria for extending atomic force microscopy, or AFM, beyond its familiar roles in imaging and local material characterization. AFM indentation works by lowering a flexible cantilever into a sample and recording how the probe deflects in response to contact. A laser reflected from the cantilever is directed onto a position-sensitive photodiode, which monitors and records the cantilever deflection.

The AFM output was subsequently converted into force–indentation curves, which researchers fitted with a contact model to estimate properties such as Young’s modulus. That modulus represents a material’s intrinsic elasticity, whereas apparent stiffness is the slope of the force–indentation curve and therefore also incorporates the mechanical environment surrounding the specimen. That distinction matters because a rigid support beneath a soft specimen resists the same indentation and can make the material appear stiffer than it is.

The effect is commonly treated as an artifact in conventional AFM, but the study deliberately used it as a signal. In earlier work, this substrate effect allowed the turgor pressure of bacterial and plant cells to be inferred from changes in apparent stiffness. The new experiment asked whether a related response could be detected in a larger tissue-like structure and, more specifically, whether it could reveal pressure transmitted through a corneal surrogate.

The artificial cornea was a homogeneous proprietary material with a Young’s modulus of approximately 25 kilopascals, a value the investigators said was comparable to their earlier measurements on cadaveric corneas. It was mounted in a custom sealed-end pressure chamber and indented at its apex with a custom AFM system driven vertically at 15 micrometres per second. The pressure transducer covered 0 to 0.1 bar, or 0 to 75 mmHg, with a stated static accuracy of ±0.1% and a total error band of ±0.25%.

Representative recordings were within approximately ±0.3 mmHg of the target pressures. At least ten repeated measurements were acquired at each of the three pressure levels, with indentation remaining below 2.50 micrometres. Only approach data were analysed.

The initial nonlinear region of each force–indentation curve was fitted with a Hertzian model for a spherical indenter, using an assumed Poisson’s ratio of 0.49, while a manually selected linear region was used to calculate apparent stiffness. Fourteen commercially obtained tipless probes were used first to examine working length and spring constant as separate variables. Their working lengths ranged from 90 to 130 micrometres, and their spring constants were measured before and after any modification using thermal power spectral density analysis.

Eight additional probes were fitted with epoxy-mounted glass beads measuring 50 to 100 micrometres in diameter, creating spherical indenters whose radii were determined from microscope images. Among the tipless probes, spring constant had a marked influence on both measured outcomes. At 15 mmHg, spring constant correlated significantly with apparent stiffness (p less than 0.001) and with Young’s modulus (p less than 0.05).

Adding spring constant to statistical models that already included working length raised the explained variance from 0.01–0.07 to 0.425–0.542 for apparent stiffness and from 0.001–0.034 to 0.427–0.476 for Young’s modulus. All likelihood-ratio comparisons were significant at p less than 0.001. By comparison, working length alone was a weak predictor.

One 130-micrometre probe nevertheless produced an estimated modulus of 508.0 kPa at 35 mmHg, with a 95% confidence interval of 416.3–599.8 kPa, versus 327.5 kPa for the 90-micrometre probe and 321.7 kPa for the 110-micrometre probe. Geometry became more consequential after the spherical indenters were added. Across modified probes with medium and high spring constants, the ratio of working length to indenter radius was positively associated with apparent stiffness and modulus.

This did not hold for very low spring constants, which the authors attributed to an inability to generate enough force for adequate indentation, leaving measurements dominated by the instrument’s threshold rather than tissue mechanics. A modified probe with a spring constant of 36.39 N/m, a 34-micrometre indenter radius and a 40-micrometre working length gave the most robust response. Its working-length-to-radius ratio was 1.2, the lowest in the high-spring-constant group.

Yet a second probe with a similar spring constant of 35.36 N/m did not behave equivalently, demonstrating that high stiffness alone was insufficient to guarantee reliable pressure detection. Adding a spherical bead also changed how the measurements responded to pressure. At spring constants around 8.2 N/m, tipless probes produced higher apparent stiffness and modulus estimates than modified probes, whereas the difference was not evident near the lower end of the tested spring-constant range.

The authors proposed that the bead shortened the effective working length and restricted bending, while its expanding contact area produced nonlinear Hertzian mechanics concentrated near the center of contact. A tipless probe instead acted more like a flat punch over a broader region. They therefore proposed that tipless designs may better capture bulk corneal behavior, whereas spherical tips may emphasize localized compression, although this distinction requires further testing.

The findings remain preliminary because the pressure-sensitive response was demonstrated in a manufactured, homogeneous surrogate rather than living or postmortem human corneal tissue. Native corneas contain collagen architecture, cell interactions, hydration gradients and regional variations that the artificial material does not reproduce. The investigators also applied a spherical-contact model to tipless probes, manually selected the transition between nonlinear and linear curve regions, assumed a Poisson’s ratio and tested spring constants no higher than 37 N/m.

Visual positioning at the corneal apex also introduced variability, and measurements away from that site may be needed to avoid artifacts caused by membrane displacement. The study therefore demonstrates a design strategy in a controlled model rather than a validated method for measuring intraocular pressure in patients. The long-term objective is to use pressure-dependent stiffness changes in the cornea as a possible route to intraocular-pressure measurement, including pressure differences on the order of 1 mmHg that may be relevant to glaucoma monitoring.

It also did not test healthy people or animals, and it did not show that AFM could replace established tonometry. What the experiments do show is that the pressure signal depends strongly on how the probe is built: a high spring constant can improve coupling to a pressurized substrate, but effective working length and contact geometry may determine whether that signal remains measurable across the pressure range. Confirming those criteria in postmortem corneas will be the next essential step before the method can be evaluated in more biologically realistic tissue.

Subject of Research: Experimental optimization of AFM cantilevers for detecting pressure beneath an artificial cornea

Article Title: Optimization of Atomic Force Microscopy Cantilever Specifications for Pressure Measurement in Biological Tissues

Article References: deHaseth, N. H., Penarredonda, A., Orlando, G., Infante, M., Rodriguez, O. G., Moy, V. T., Knight, O. J., & Ziebarth, N. M. (2026). Optimization of Atomic Force Microscopy Cantilever Specifications for Pressure Measurement in Biological Tissues. Annals of Biomedical Engineering. https://doi.org/10.1007/s10439-026-04420-2

Image Credits: AI Generated

DOI: 10.1007/s10439-026-04420-2

Keywords: atomic force microscopy, cantilever design, artificial cornea, pressure sensing, intraocular pressure, corneal biomechanics, apparent stiffness, substrate effect, nanoindentation, spring constant, Optimization, Atomic

The team, led by Man Lei and corresponding author Haibin Xue, took granite specimens from the Qinling Tunnel of the Hanjiang-to-Weihe River Valley Water Diversion Project in China, a massive engineering undertaking that brings water from the Yangtze basin to the Yellow River basin. All specimens came from the same rock mass, ensuring a consistent starting point. The researchers cut the granite into cuboids and then polished them on a metallographic polisher using abrasive papers ranging from 100 to 7000 mesh, with each grit applied for at least 10 minutes and the finest grit for no less than 20 minutes. The goal was to produce surfaces flat and smooth enough for nanoindentation testing, a technique that demands near-perfect specimen preparation. The polished samples were then ultrasonically cleaned in absolute ethanol and dried in an oven at 50 degrees Celsius for at least 24 hours to guarantee complete dryness before any chemical exposure began.

Once prepared, the granite specimens were immersed in 0.1 mol/L sodium chloride solutions adjusted to pH values of 3, 5, 7, 9 and 11, using hydrochloric acid and sodium hydroxide to set the acidic and alkaline conditions respectively. Distilled water at pH 7 served as a neutral control. The solutions were held in 500 mL wide-mouth bottles, with eight specimens laid flat on the bottom of each bottle in 250 mL of corrosive liquid. The immersion durations were 30, 60, 90 and 120 days, spanning four months of continuous chemical attack. The entire experiment ran at temperatures between 17 and 23 degrees Celsius, so thermal effects could be excluded from the analysis. After each soaking period, the corroded specimens were polished and dried again before nanoindentation tests were performed using an Agilent Nano Indenter G200 equipped with a Berkovich diamond tip.

Nanoindentation works by pressing a diamond tip into a material’s surface while continuously recording the applied load and the corresponding penetration depth. In the loading stage, the material undergoes both elastic and plastic deformation simultaneously. During unloading, the recovered elastic deformation provides the basis for calculating mechanical properties such as elastic modulus and hardness. The contact stiffness—the slope of the upper segment of the unloading curve at maximum penetration depth—is the key parameter that links the measured load-displacement data to the reduced modulus and, ultimately, the specimen’s true elastic modulus. The instrument used in this study had a load resolution of 50 nanonewtons and a displacement resolution of 0.01 nanometers, allowing extremely fine measurements of how each mineral grain responds to chemical corrosion. The researchers deployed grid indentation arrays with 100 indentation points per mineral per condition, spaced 100 micrometers apart, to generate statistically robust averages for quartz, feldspar and mica.

The results revealed that the pH of the solutions shifted noticeably during the early stages of corrosion as intensive water-rock reactions took place, before stabilizing in later stages. Neutral and alkaline solutions ended up weakly alkaline, attributed to the high alkali feldspar content of the granite generating hydroxide ions. Acidic solutions drifted toward near-neutral pH as hydrogen ions were consumed by reactions with the rock minerals. Precipitate morphologies also evolved over time: in the pH 3 solution, massive off-white floccules appeared within 10 days, peaked between 60 and 90 days, and declined thereafter, while the pH 11 solution produced abundant reddish-brown coarse particles as early as 10 days. Distilled water generated only slight turbidity and trace black precipitates over the full 120 days, confirming that pure water alone imposes minimal chemical damage on granite’s constituent minerals.

Scanning electron microscopy provided direct visual evidence of how each mineral grain corroded. After 120 days in the pH 3 solution, mica surfaces displayed abundant layered microcracks and uneven roughness, while feldspar formed step-like dissolution terraces along with fine cracks. In the pH 11 solution, quartz surfaces developed numerous irregular etch pits. These distinct corrosion signatures—microcracks, dissolution terraces and etch pits—correspond directly to the chemical compositions of the minerals and the concentrations of hydrogen and hydroxide ions in the surrounding solutions. Minerals with well-developed pore structures reacted faster with corrosive solutions, while those with poorly developed pores corroded at much lower rates, meaning that pore architecture dictated the kinetic rate of hydrochemical attack.

The nanoindentation data showed that elastic modulus and hardness degradation varied dramatically across the three minerals and across solution chemistries. In distilled water, quartz and feldspar suffered only minor modulus attenuation, but mica—due to its relatively high porosity—experienced severe degradation, with a rapid decrease during the first 60 days followed by a slower decline. In acidic solutions, quartz showed nearly linear modulus attenuation, while feldspar and mica degraded rapidly in the initial immersion stage before the rate declined. In alkaline solutions, all three minerals underwent rapid initial modulus loss that gradually slowed. The hardness results followed similar patterns: quartz suffered the most severe hardness loss under alkaline conditions, intensifying with rising alkalinity, whereas feldspar and mica underwent more pronounced hardness reduction in acidic solutions, worsening with increasing acidity.

To quantify the damage, the researchers adopted the Kachanov-Rabotnov damage variable framework and Lemaitre’s strain equivalence principle, defining scalar damage variables based on the ratio of pre- and post-corrosion elastic moduli and hardness values. The results were striking. After 120 days in the strongly acidic pH 3 solution, mica’s elastic modulus damage variable reached approximately 0.29, while its hardness damage variable climbed to 0.65—meaning mica’s hardness degraded more than twice as fast as its elastic modulus under acidic attack. For quartz, both damage variables increased with rising solution pH, confirming that hydroxide ions in alkaline solutions corrode quartz more severely. For feldspar, damage increased as pH decreased, indicating stronger corrosion by hydrogen ions. The elastic modulus damage variable exceeded the hardness damage variable for feldspar, suggesting its stiffness degrades faster than its hardness during immersion.

Using bivariate least-squares fitting, the team established damage evolution equations for elastic modulus and hardness as functions of both pH and soaking duration for each mineral, with coefficients of determination ranging from 0.979 to 0.997—exceptionally high fits that make the equations practical predictive tools. These equations allow engineers to estimate how much stiffness and hardness a given granite mineral will lose after a specified exposure time in a solution of known pH, without needing to run months of laboratory immersion tests. The researchers suggest the findings can provide a scientific reference for evaluating the mechanical degradation and durability of granite in acid rain and saline environments, conditions increasingly relevant as industrial development accelerates water pollution and yields hydrochemical environments with high concentrations of acids and alkalis.

The broader implications extend across geotechnical engineering, tunnel design and dam foundation safety. Long-term immersion in deep groundwater weakens the bonding force between mineral particles through water film lubrication, mineral dissolution and other effects, and prior studies have shown that clay hydration, pyrite oxidation and carbonate dissolution can further exacerbate internal structural degradation in other rock types. By isolating the micromechanical mechanism of granite’s degradation—reactions between solution ions and mineral grains that precipitate reaction products, raise porosity and generate cracks—the study reveals how macroscale weakening emerges from nanoscale chemistry. As underground infrastructure ages in chemically aggressive groundwater, understanding which minerals fail first, and under which pH conditions, could help engineers predict where and when granite structures will lose strength, before the damage becomes visible at the surface.

Subject of Research: Study on the micromechanical properties and damage model of granite under hydrochemical environments based on nanoindentation tests

Article Title: Study on the micromechanical properties and damage model of granite under hydrochemical environments based on nanoindentation tests

Article References: Lei, M., Xue, H., Dang, F.-N., & Ding, W. (2026). Study on the micromechanical properties and damage model of granite under hydrochemical environments based on nanoindentation tests. Frontiers in Earth Science, 14, Article 1874086. https://doi.org/10.3389/feart.2026.1874086

Image Credits: AI Generated

DOI: 10.3389/feart.2026.1874086

Keywords: micromechanical, properties, damage, model, granite, under, hydrochemical, environments, based, nanoindentation, tests, scientific research

The technique at the heart of the study is nanoindentation, a method borrowed from materials science in which a pyramid-shaped diamond tip is pressed into a polished surface with exquisite precision. The instrument records how deeply the tip penetrates under a known load and how the material pushes back during unloading. From these measurements, researchers calculate Young’s modulus, a quantity that describes how stiff a material is: the higher the value, the more the material resists elastic deformation. Using a Berkovich tip under a load of just two millinewtons, with indentation points spaced eight micrometres apart, the team produced detailed maps of skull stiffness across regions barely wider than a human hair.

The study focused on three living species of the endemic genus Gallotia: the small Atlantic lizard G. atlantica from Lanzarote and Fuerteventura, the intermediate-sized Tenerife lizard G. galloti, and the larger Gran Canaria giant lizard G. stehlini. Five specimens were analysed, including two juveniles of G. stehlini, each embedded in cold-curing epoxy resin and polished to a mirror finish with progressively finer abrasive papers and colloidal silica. The researchers probed eleven areas on each skull, covering seven bone regions such as the premaxilla, parietal, quadrate, pterygoid and dentary, two cranial sutures, and two tooth-related zones of dentine and enamel.

The results were strikingly patterned. Tooth enamel, unsurprisingly, was by far the stiffest material tested, with values often exceeding sixty gigapascals, while the cranial sutures consistently registered the lowest values, highlighting their role as flexible joints within an otherwise rigid frame. More intriguing was the finding that bone stiffness did not differ significantly across the seven cranial regions examined. A statistical analysis using linear mixed models, which properly accounted for the many repeated measurements nested within each skull, found no meaningful differences among bone areas. In effect, the skull bone of these lizards behaves as a broadly uniform material, at least at the scale relevant to whole-skull mechanics.

Yet when the researchers compared species, a clear trend emerged: the smaller the skull, the stiffer the bone. The tiniest specimen, an adult G. atlantica with a skull only about nineteen millimetres long, showed the highest average stiffness at roughly 24 gigapascals, while the largest, an adult G. stehlini with a skull of 61 millimetres, averaged around 17 gigapascals. The statistical model confirmed a significant negative relationship between skull length and stiffness. The team proposes that this pattern reflects diet. G. atlantica, living in arid islands near the African coast, feeds heavily on hard-shelled prey such as beetles and snails, demanding robust cranial bone. G. stehlini, by contrast, is largely herbivorous, eating leaves and seeds that require less skull reinforcement.

Predation pressure may add a second layer of explanation. Small lizards face attacks from a wider array of predators, including shrikes, kestrels, hedgehogs and cats, whereas the giants of the genus evolved in a world with few threats. Intriguingly, the finite element simulations showed that G. galloti, which is not the species eating the hardest food, nonetheless displayed the lowest stress values under identical biting loads, suggesting its skull geometry makes it the most structurally resistant of the group. The authors suggest that protection against predation may have shaped its comparatively robust cranium, possibly helping explain why this species thrives across several islands and occupies a broad range of ecological niches.

The simulations themselves represent a substantial technical achievement. Each lizard skull was micro-CT scanned, digitally segmented and converted into computer models containing up to two and a half million nodes. Muscle forces were calculated from the physiological cross-sectional areas of ten major jaw muscles and applied along vectors running from each muscle’s origin to its insertion. The models then simulated bilateral biting, comparing two scenarios: one in which bone was assigned a single averaged stiffness value, and another in which the experimentally measured regional values were smoothly interpolated across the skull. The verdict was clear. Both approaches produced nearly identical patterns of stress and strain, meaning a simple homogeneous model captures the global biomechanics of these skulls just as well as a complex heterogeneous one.

This finding matters far beyond the Canary Islands. Biomechanical models of extinct animals have long been handicapped by uncertainty about the material properties of fossil bone, which is rarely preserved in a state that allows direct testing. Palaeontologists typically borrow stiffness values from cows, birds or crocodiles, introducing potentially large errors. The new study demonstrates an elegant workaround: because stiffness varies predictably with skull length within Gallotia, the researchers could use their statistical model to estimate bone stiffness in the extinct giants G. goliath and G. auaritae from skull measurements alone. The predicted values, between roughly 14.6 and 16.2 gigapascals, sit at the soft end of the spectrum observed in living relatives.

Applied to a finite element model of G. goliath, these estimates painted a revealing picture. The extinct giant showed low stress in the front of the skull but high stress concentrated in the vomer, palatal bones and lateral pterygoids, a pattern consistent with a shift toward herbivory as body size increased under the so-called island rule. This ecological principle holds that island animals often evolve extreme body sizes when resources are abundant and predators and competitors are scarce, as was the case in the pre-human Canary Islands. The comparatively less reinforced skull of G. goliath fits the expectation that large herbivorous lizards simply do not need the bone strength required to crush hard-shelled invertebrates.

The broader significance of the work lies in its methodological message. For researchers modelling the functional morphology of extinct vertebrates, the study provides evidence that averaged material properties can be adequate when the biological question concerns overall mechanical performance, while regionally specific data remain valuable when local stress details are the focus. It also opens a window onto conservation biology: several living Gallotia species, including G. simonyi and G. bravoana, are critically endangered, and understanding how their skulls evolved under island conditions may inform how they are protected today. By connecting nanometre-scale measurements to evolutionary patterns spanning millions of years, the study shows that even the smallest poke can illuminate the biggest questions about how life diversifies on islands and why some of its most spectacular experiments, like the giant lizards of the Canaries, ultimately failed to survive the arrival of humans.

Subject of Research: Skull bone stiffness and biting biomechanics in living and extinct Canary Island lizards

Article Title: Lizards under pressure: skull nanoindentation in an insular reptile for palaeobiological inference

Article References: Garcia-Escolà, L., Marcé-Nogué, J., de Celis, A., Cuadrado, N., Vidales, E., Cruzado-Caballero, P., Serrano-Martínez, A., Castillo-Ruiz, C., & Fortuny, J. (2026). Lizards under pressure: skull nanoindentation in an insular reptile for palaeobiological inference. Swiss Journal of Palaeontology, 145, 881-900. https://doi.org/10.3897/sjp.145.193019

Image Credits: AI Generated

DOI: 10.3897/sjp.145.193019

Keywords: Gallotia, Canary Islands, nanoindentation, finite element analysis, biomechanics, lizards, palaeontology, Young's modulus, island rule, cranial bone, extinct giant lizard, functional morphology

The research, led by Yingying Zhao, Shengchang Zhang, Qibin Xu, Mengjin Jiang, and Pengqing Liu of the College of Polymer Science and Engineering at Sichuan University, together with Krishnan Jayaraman of the University of Auckland, tackles a problem that has stubbornly resisted experimental analysis. At the boundary where a basalt fiber meets a polymer matrix, several factors operate simultaneously: the chemical groups grafted onto the fiber surface, the nanoscale roughness of that surface, and the way resin molecules arrange themselves in response. In a real composite, all of these effects are entangled. Measure the strength of an interface and you cannot easily tell whether the credit belongs to chemical bonding, to mechanical interlocking, or to something subtler still. The Sichuan University team’s solution was to decouple these influences using atomistic simulations, allowing each factor to be varied and evaluated in isolation.

Central to the study is a workhorse of composite chemistry: the silane coupling agent known as gamma-aminopropyl triethoxysilane, or KH550. Coupling agents are molecular intermediaries, molecules designed with one end that bonds to an inorganic surface and another that is compatible with organic polymers. KH550 carries amino groups, which are rich in nitrogen and hydrogen atoms capable of forming hydrogen bonds with surrounding resin chains. Using computational simulations, the researchers showed that KH550 does something rather elegant on the basalt fiber surface: it balances highly positive and highly negative electrostatic regions, creating multiple binding sites where resin molecules can attach. In effect, the coupling agent transforms a chemically patchy surface into a welcoming landscape for polymer chains.

The quantitative results are striking. At the interface between basalt fiber and polyamide 66, a common engineering thermoplastic, KH550 modification increased the number of hydrogen bonds by 10.4 percent. More tellingly, the interfacial interaction energy, a measure of how strongly the two phases attract each other, became more negative, shifting from -384.4 to -487.9 kilocalories per mole. In the language of molecular simulation, a more negative interaction energy means a more stable, more tightly bound interface. That single modification, applied at the molecular scale, produced a measurable and substantial strengthening of the chemical handshake between fiber and resin.

But chemistry alone was only half the story, and this is where the study’s decoupling approach proves its worth. The researchers examined three different composite systems: basalt fiber with polyamide 66, basalt fiber with epoxy resin, and basalt fiber with polypropylene. Across these systems, they separated the contributions of KH550’s amino groups from the contributions of surface morphology, the atomic-scale texture of the fiber surface. The verdict was consistent: the chemical interactions provided by the amino groups contributed more to interfacial mechanical enhancement than surface morphology did. At the basalt fiber and polyamide 66 interface specifically, introducing amino groups enhanced the interfacial mechanical response by a factor of 1.49, while modifying the atomic-scale morphology enhanced it by a factor of 1.29. Both matter, but chemistry leads.

Perhaps the most intriguing finding concerns how surface texture influences the resin itself. The simulations revealed that for both the polyamide 66 and epoxy systems, atomic-level surface morphology regulates the arrangement, or conformation, of resin molecular chains, and that this effect optimizes mechanical properties more effectively than larger surface asperities that simply allow resin to infiltrate surface irregularities. In other words, the classical picture of mechanical interlocking, where rough surfaces grip the polymer like microscopic Velcro, is not the dominant mechanism at these scales. Instead, the fine texture of the surface shapes how polymer chains fold and orient, and those conformations determine how load is transferred across the interface.

KH550 also orchestrates a dramatic reorganization of the resin. According to the simulations, the coupling agent transforms resin molecular chains from conformations that lie aligned along the fiber surface into interpenetrating structures that reach into the matrix. The researchers attribute this to two combined effects: enhanced interaction between the amino groups and the resin, and steric hindrance, the physical crowding that prevents chains from lying flat against the surface. The result is a molecularly interlocked interphase, a region where fiber and polymer are no longer simply touching but genuinely entangled at the chain level.

To connect these molecular pictures to measurable mechanics, the team performed atomic-scale nanoindentation simulations, a computational analogue of the classic hardness test in which a sharp tip presses into a material to probe its resistance to deformation. The results revealed a fundamental shift in how the material fails. In unmodified interfaces, the resin deformed by sliding along the interface, a mode that ultimately leads to adhesive failure, where the bond between fiber and matrix simply gives way. After KH550 modification, deformation was redirected into the bulk of the matrix itself, a transition that shifts failure from adhesive to cohesive. Cohesive failure, in which the polymer itself must tear rather than the bond peeling apart, is generally the more desirable mode because it means the interface is no longer the weakest link. The maximum indentation force rose from approximately 2.9 to 4.0 nanonewtons, a roughly 38 percent increase attributable to the molecular redesign of the interphase.

The significance of this work extends well beyond basalt fiber. Fiber-reinforced composites of every kind, from glass and carbon to natural fibers, depend on the same delicate interfacial chemistry, and designers have traditionally improved interfaces by trial and error, testing coupling agents and surface treatments empirically. By rigorously separating the roles of chemical functionality, atomic-scale morphology, and resin conformation, the study provides something rarer: a mechanistic roadmap for rational interphase design. It tells engineers which lever to pull first. If chemistry contributes more than texture, then investment in tailored coupling agents and surface functionalization should take priority over aggressive roughening treatments, and the choice of coupling agent should be matched to the electrostatic and hydrogen-bonding character of the specific resin.

There are also practical implications for sustainability and materials selection. Basalt fiber is produced from abundant volcanic rock without the energy-intensive precursor chemistry required for carbon fiber, and it is compatible with a range of resins, from commodity polypropylene to high-performance epoxies and polyamides. The finding that the same coupling agent strategy strengthens interfaces across polyamide 66, epoxy, and polypropylene systems suggests a versatile design principle that could accelerate the adoption of basalt composites in automotive parts, wind turbine components, construction materials, and consumer products. As the authors note, the research clarifies the intrinsic interfacial strengthening mechanism and provides guidance for rational interphase design. What was once an opaque tangle of competing effects is now a decoupled, quantified, and ultimately engineerable set of levers, and that clarity may prove to be the most valuable property of all.

Subject of Research: Interfacial strengthening mechanisms in basalt fiber-reinforced polymer composites

Article Title: Decoupling of factors influencing interface characteristics in basalt fiber-reinforced polymer composites

Article References: Zhao, Y., Zhang, S., Xu, Q., Jayaraman, K., Jiang, M., & Liu, P. (2026). Decoupling of factors influencing interface characteristics in basalt fiber-reinforced polymer composites. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02118-6

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02118-6

Keywords: basalt fiber, polymer composites, silane coupling agent, KH550, interface, hydrogen bonds, molecular simulation, nanoindentation, polyamide 66, epoxy resin, interphase design, surface morphology

The problems do not stop at water uptake. The old adhered mortar is riddled with pores and microcracks that act as stress concentrators and preferential pathways for water and aggressive ions, weakening the bond between aggregate and new cement paste. Even when the aggregate is fully saturated, only 16 to 36 percent of the absorbed water is released back at high relative humidity, so high absorption does not guarantee useful internal curing. A research team led by Zedong Qiu and Shuang Lu, publishing in Case Studies in Construction Materials, has now tested a deceptively simple idea: instead of trying to repair the aggregate before mixing, use its porous structure as a temporary chemical reservoir that feeds reactive silicate into the hydrating cement from the inside.

The strategy hinges on replacing the water normally used to pre-wet the aggregate with a sodium silicate solution of the same volume. Sodium silicate is chemically attractive because dissolved silicate ions react with calcium ions and portlandite, the calcium hydroxide that cement hydration produces in abundance, to form additional calcium silicate hydrate gel, the glue-like binding phase of concrete. Previous approaches either stirred sodium silicate directly into the mixing water, which can cause rapid flow loss and early flocculation, or soaked aggregates for many hours and dried them, which consumes time and energy. The new procedure pre-wets the aggregate for just three hours and then mixes it into mortar without any drying step at all.

The experiments were carefully controlled. Recycled fine aggregate was produced by crushing a parent concrete with a compressive strength of 40 megapascals and sieving to particles between 1.18 and 2.35 millimetres. The pre-wetting liquid volume was fixed at 85 percent of the aggregate’s saturated surface-dry water absorption, and solutions containing 5, 10, 15 and 20 percent sodium silicate by mass were compared against a water-only reference. Total water in every mortar was held constant at 262.36 grams per 500 grams of cement, so any difference in performance could be attributed to the chemistry of the stored liquid rather than to changes in mix proportions.

The first surprise is what did not happen during those three hours. Thermogravimetric analysis and scanning electron microscopy showed no systematic consumption of portlandite and no progressive build-up of a gel-rich surface layer as concentration increased. The aggregate surfaces retained their heterogeneous character, with open depressions, exposed particles and unfilled pore-like defects, and portlandite crystals remained visible even at the highest concentration. In other words, the treatment did not rebuild the aggregate before mixing. Instead, extraction tests in deionized water proved that a releasable silicate fraction remained locked inside. Silicate concentrations in the extract rose steadily over 24 hours without reaching a plateau, and the background-corrected concentration after 24 hours increased almost perfectly linearly with the pre-wetting concentration, with a coefficient of determination of 0.981. The porous aggregate was behaving exactly as intended: a carrier, not a reactor.

That spatial confinement paid off immediately in the fresh mortar. Direct addition of sodium silicate typically causes rapid flow loss because soluble silicate reacts with calcium in the bulk paste, triggering early precipitation and flocculation. Here, the opposite occurred: the sodium-silicate mortars showed slightly higher initial flowability than the water-pre-wetted reference, because the silicate was initially trapped inside the aggregate pores and only a limited fraction reached the continuous paste during the short interval before the flow test. Pore storage effectively separated the introduction of reactive silicate from its reaction in both space and time.

Once mixing began, the stored silicate started to work. Isothermal calorimetry showed that higher silicate loadings advanced the onset of the main hydration peak, and the mortar pre-wetted with the 20 percent solution shortened its acceleration period to 8.98 hours, 27.35 percent below the reference. A Krstulovic-Dabic kinetic analysis revealed that all mortars followed the same sequence of nucleation-and-growth, phase-boundary and diffusion-controlled stages, but the rate constants shifted. The nucleation-stage rate constant rose by roughly 16.9 percent at the highest loading, consistent with silicate released from the pores raising local supersaturation and providing extra nucleation sites for calcium silicate hydrate. Crucially, however, the strongest early kinetics did not produce the best overall reaction: the highest extrapolated maximum heat release belonged to the 10 percent mixture, not the 20 percent one, because excessively rapid early precipitation at high concentrations hindered later mass transport and reaction.

The 10 percent formulation emerged as the clear winner across nearly every measurement. Its 28-day mass loss associated with bound water in hydrates was about 16.5 percent higher than the reference, while its portlandite content was the lowest, indicating that stored silicate had been consumed in secondary gel formation rather than merely accelerating clinker hydration. Solid-state silicon-29 nuclear magnetic resonance spectroscopy added molecular-level detail: the 10 percent mortar showed the lowest fraction of isolated silicate tetrahedra from unhydrated clinker and the highest fraction of more connected Q3 environments, while the 15 percent mixture produced the longest mean silicate chains in the calcium silicate hydrate. Compressive strength followed suit, with the 10 percent mixture gaining 29.52 percent at 3 days and 15.13 percent at 28 days over the reference, while the 20 percent mixture actually fell below the reference at early age.

The interfacial evidence is perhaps the most striking. Backscattered electron imaging and energy-dispersive spectroscopy showed that the calcium-to-silicon ratio of the interfacial gel dropped from a median of 2.15 to 1.88, with a narrower spread, indicating a more uniform, silicon-rich gel along the aggregate boundary. Segmented image analysis revealed that unhydrated cement near the interface fell from 11.41 to 6.88 percent of the area, coarse portlandite clusters shrank dramatically, and the estimated width of the interfacial transition zone narrowed from roughly 35 to 20 micrometres, a reduction of about 43 percent. Nanoindentation mapping across the interface showed the median indentation modulus rising from 26.17 to 33.66 gigapascals and hardness from 744 to 1142 megapascals, increases of 28.6 and 53.5 percent respectively, with the fraction of high-stiffness matrix within 24 micrometres of the aggregate surface jumping from 16.67 to 72.73 percent. Mercury intrusion porosimetry completed the picture: total porosity fell from 18.82 to 14.22 percent, a 24.4 percent reduction, with pore volume shifting decisively from pores larger than 200 nanometres into the harmless sub-20-nanometre range.

The broader significance lies in the elegance of the mechanism. Rather than spending energy drying, calcining or carbonating recycled aggregate, the method exploits the very property that makes recycled sand troublesome, its open pore network, and turns it into a delivery system for chemistry that strengthens the weakest zone of the composite. The aggregate pre-wetting and the hydration regulation become a single step with no drying stage, and the optimum dosage sits at a moderate 10 percent where early activation and sustained silicate supply are balanced. If the approach scales from laboratory mortars to real concrete production, it could help close the loop on construction and demolition waste, turning porous, water-hungry rubble into an asset that builds its own stronger interface from the inside out.

Subject of Research: Sodium silicate pre-wetting of recycled fine aggregates to strengthen the interfacial transition zone and micromechanics of recycled mortar

Article Title: Sodium silicate pre-wetting of recycled fine aggregates for interfacial reconstruction and micromechanical strengthening of recycled mortar

Article References: Qiu, Z., Lv, M., Chen, Z., Liao, Y., Zhu, X., & Lu, S. (2026). Sodium silicate pre-wetting of recycled fine aggregates for interfacial reconstruction and micromechanical strengthening of recycled mortar. Case Studies in Construction Materials, 25, Article e06614. https://doi.org/10.1016/j.cscm.2026.e06614

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06614

Keywords: recycled fine aggregate, sodium silicate, pre-wetting, interfacial transition zone, calcium silicate hydrate, cement hydration kinetics, nanoindentation, porosity, construction and demolition waste, recycled mortar, C-S-H gel, sustainable construction

The research, carried out by Thi-Nhai Vu of Nha Trang University and Van-Trung Pham and colleagues at the University of Danang – University of Science and Technology in Vietnam, relies on molecular dynamics simulations, a technique that tracks the motion of every individual atom in a material by solving the classical equations of motion under an interatomic potential. Rather than testing bulk samples in a mechanical testing frame, the team simulated nanoindentation, the process of pushing a hard, sharply pointed tip into a material and measuring its resistance. Nanoindentation is the standard method for probing hardness and elastic modulus at very small length scales, and by reproducing it atom by atom, the researchers could watch dislocations nucleate, grain boundaries slide, and stacking faults spread in real time, something no laboratory microscope can capture with such completeness.

The first major finding concerns the celebrated Hall-Petch relationship, one of the oldest rules in metallurgy. For more than half a century, engineers have known that shrinking the grains of a polycrystalline metal makes it harder, because grain boundaries act as obstacles that block the glide of dislocations, the line defects responsible for plastic flow. The simulations confirmed this classic strengthening trend in CoCuFeNiPd alloys with larger grains, where plastic deformation was dominated by dislocation activity nucleated near the indenter tip and propagating through the crystal interior. But when the grain size was reduced into the ultrafine nanocrystalline regime, the trend reversed dramatically. Hardness and the reduced Young’s modulus began to fall rather than rise as grains became smaller, a phenomenon known as inverse Hall-Petch behavior.

The reason for this reversal, revealed directly by the atomic-scale trajectories, is a change in the dominant deformation mechanism. In the inverse Hall-Petch regime, grains have become so small that dislocations can no longer pile up effectively against boundaries; instead, the material deforms by grains sliding past one another along their shared boundaries and by whole grains rotating under the indenter’s pressure. Grain boundary sliding and grain rotation allow the material to accommodate strain without the intense dislocation activity that characterizes conventional plasticity. This mechanistic crossover has been observed in other nanocrystalline metals and ceramics, but the present study pins down how it plays out in a chemically complex, five-element high-entropy system, where the rugged energy landscape created by chemical disorder adds further obstacles to dislocation motion.

The second variable the team explored was the palladium concentration, denoted by the subscript x in CoCuFeNiPdx. Palladium is the largest and heaviest of the five elements in this alloy family, and adding it increases what metallurgists call lattice distortion: the local warping of the crystal lattice caused by atoms of different sizes trying to share the same lattice sites. The simulations showed that increasing Pd content enhances both hardness and indentation resistance. The mechanism is twofold. First, stronger lattice distortion raises the frictional resistance that dislocations experience as they move through the lattice, effectively making the entire crystal a rougher terrain for defect motion. Second, higher palladium levels promote short-range ordering, a subtle chemical phenomenon in which atoms of particular species preferentially occupy neighboring sites, creating local patterns within the nominally random solid solution. These ordered domains act as additional barriers that significantly impede dislocation glide, a strengthening route that has attracted intense interest since recent experimental and computational work demonstrated that short-range order can simultaneously boost the strength and ductility of high-entropy alloys.

However, the study also uncovered a cautionary limit. When the palladium content becomes excessive, the alloy begins to undergo local phase separation, with palladium-rich regions segregating from the rest of the matrix. This chemical inhomogeneity suppresses the material’s ability to accommodate strain, undermining the very ductility and damage tolerance that make high-entropy alloys attractive in the first place. The message for alloy designers is that palladium is a powerful strengthening agent only up to an optimum concentration; beyond that point, the benefits of lattice distortion and short-range ordering are outweighed by the embrittling effects of compositional segregation. This kind of composition-property trade-off is exactly the information needed to guide the rational design of Pd-containing HEAs for real applications.

Temperature emerged as the third decisive factor. As the simulation temperature increased, the alloys exhibited pronounced thermal softening, with both hardness and elastic modulus declining. Elevated temperature promotes structural disorder, thermally shaking atoms out of their ideal lattice positions and weakening the short-range order that had helped block dislocations. At the same time, the increased atomic disorder interferes with the propagation of dislocations in a different way, scattering and absorbing them before they can carry plastic deformation efficiently across grains. The net result is a material that yields more easily and deforms more diffusely at high temperature, an important consideration for any application in which nanoscale contact occurs under thermal load, such as microelectromechanical systems, high-temperature coatings, or cutting tools.

Perhaps the most valuable contribution of the work is its unified atomic-scale picture of how these mechanisms couple. The researchers demonstrate that nanoindentation-induced deformation in CoCuFeNiPdx alloys is never governed by a single process but by the simultaneous evolution of grain boundary activity, dislocation nucleation, stacking fault formation, and amorphous transformation, the latter being the local loss of crystallinity under the extreme contact pressures beneath the indenter tip. Stacking faults, which are planar packing defects in the face-centered cubic lattice, appear as intermediate carriers of plasticity between perfect dislocation slip and full amorphization. Which of these channels dominates depends on grain size, composition, and temperature, and the simulations show how shifts in one variable can redirect the entire deformation pathway. This mechanistic map gives experimentalists concrete signatures to look for, for example in transmission electron microscopy of indented regions, and gives modelers benchmarks against which to validate larger-scale simulations.

The study also situates itself within a rapidly growing literature on high-entropy alloys, a field launched in 2004 when independent groups led by Jien-Wei Yeh and Brian Cantor first reported the surprising stability and properties of multi-principal-element alloys. In the two decades since, HEAs have been explored for structural, cryogenic, irradiation-resistant, and high-temperature applications, and concepts such as the four core effects of high-entropy materials, including severe lattice distortion and sluggish diffusion, have been progressively clarified. Recent work has highlighted chemical short-range order as a tuning knob of exceptional power, and the present results extend that theme to the specific case of palladium-bearing CoCuFeNiPd, an alloy system that earlier simulations had already flagged as one where short-range ordering and grain boundary segregation can inhibit the onset of inverse Hall-Petch softening.

For engineers thinking about applications, the relevance is direct. Nanoscale contact governs the performance and reliability of micro- and nanoelectromechanical devices, thin-film coatings, wear-resistant surfaces, and precision machining processes. A material that maintains high hardness and elastic resilience while tolerating strain at elevated temperature is the ideal candidate for such roles, and the new results indicate how to move toward that target: choose grain sizes on the Hall-Petch side of the crossover, tune palladium content high enough to maximize distortion and ordering but low enough to avoid phase separation, and account for thermal softening in any environment where heat is present. The Vietnamese team’s atomistic tour of CoCuFeNiPd thus delivers both fundamental insight into how chemically complex crystals deform under contact and practical guidance for the next generation of high-entropy alloys designed for nanoscale service. As simulation tools and interatomic potentials continue to improve, studies of this kind are expected to play an ever larger role in screening alloy compositions before a single ingot is melted, accelerating the path from atomic-scale understanding to real-world materials.

Subject of Research: Atomic-scale simulation of grain size, palladium composition, and temperature effects on the nanoindentation behavior of CoCuFeNiPdx high-entropy alloys

Article Title: Atomic-scale investigation of grain-size, Pd composition, and temperature effects on the nanoindentation behavior of CoCuFeNiPdx high-entropy alloys

Article References: Vu, T.-N., Pham, V.-T., Tran, N.-H., Luu, D.-B., Tao, Q.-B., & Nguyen, T.-T. (2026). Atomic-scale investigation of grain-size, Pd composition, and temperature effects on the nanoindentation behavior of CoCuFeNiPdx high-entropy alloys. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13891-6

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13891-6

Keywords: high-entropy alloys, nanoindentation, molecular dynamics, Hall-Petch, grain boundary sliding, palladium, short-range ordering, lattice distortion, dislocations, thermal softening, hardness, CoCuFeNiPd

The core challenge lies in something invisible to the naked eye: the interfacial transition zone, or ITZ, the thin band of cement paste that bonds directly to the surface of each aggregate particle. In ordinary concrete, the ITZ is often the weakest region of the whole material, but coal gangue makes the problem dramatically worse. The rock is riddled with pores, bedding-related defects, pre-existing microcracks, and weak mineral regions, and its exposed surface is dominated by aluminosilicate minerals that react only weakly under normal curing conditions. Although the angular, rough texture of crushed gangue does provide good mechanical interlocking with the surrounding paste, that advantage cannot compensate for the discontinuous, mechanically feeble boundary that forms where aggregate meets binder. When water finds its way into these surface-connected defects, differences in pore structure and stiffness between the aggregate and the paste concentrate stress near the interface and invite cracks to begin exactly where the material can least afford them.

The research team attacked this weakness with three humble modifiers, all readily available in coal-mining regions: sodium silicate, silica fume, and limestone powder. Each works through a different route. Sodium silicate can penetrate and seal open pores and microdefects, while its soluble silicate species participate in reactions near the aggregate surface that improve interfacial continuity. Silica fume, an ultrafine powder of nearly pure amorphous silica, physically fills surface irregularities and interfacial voids and can later react pozzolanically to refine the surrounding cementitious products. Limestone powder contributes mainly through particle packing, heterogeneous nucleation of hydration products, and carbonate-related interactions with aluminate-bearing phases. The researchers applied each modifier at dosages of 2, 3, and 4 percent by aggregate mass, dry-mixing the powder onto washed, surface-dried gangue particles before the concrete was batched.

The concrete itself was deliberately unconventional. Instead of ordinary Portland cement, the team used a coal-based solid-waste binder containing 50 percent benchmark cement, 25 percent calcined coal gangue powder, 10 percent limestone powder, 10 percent fly ash, and 5 percent flue gas desulfurization gypsum, a formulation that turns more mining and power-plant waste into a useful building material. The calcined gangue powder was produced by heating ground raw gangue first to 500 degrees Celsius and then to 800 degrees, activating its aluminosilicate content. All mixtures shared a fixed water-to-binder ratio of 0.40 and an aggregate-to-binder ratio of 1.50, so that the only variable was the type and dosage of the surface coating. Compressive strength screening at 3, 7, and 28 days identified the best dosage for each modifier: 4 percent sodium silicate, 3 percent silica fume, and 4 percent limestone powder.

The most revealing part of the study came from nanoindentation, a technique that presses a microscopic diamond tip into a polished specimen surface to measure local stiffness point by point. The researchers ran indentation paths of 25 points, spaced 10 micrometers apart, across the aggregate, the ITZ, and the paste on either side. In every mixture, the modulus held steady at roughly 50 to 55 gigapascals inside the aggregate, plunged within the interfacial zone, bottomed out near 110 micrometers from the boundary, and then recovered toward the paste. But the depth of that plunge depended strongly on the treatment. The unmodified concrete reached a minimum of about 18 gigapascals; limestone powder raised it to 22, silica fume to 26, and sodium silicate to 33 gigapascals, the latter producing the smoothest mechanical transition across the entire interface.

Scanning electron microscopy gave those numbers a visible structure. The unmodified interface showed coarse residual particles, loose agglomerates, open pores, and discontinuous patches. Sodium silicate treatment, by contrast, produced abundant flocculent, fibrous, and fine granular products distributed around the aggregate surface, yielding a comparatively continuous and compact boundary. Silica fume yielded a more uniform fine-grained morphology, though some spherical residual particles remained visible. Limestone powder produced a heterogeneous picture, with compact product-rich regions coexisting alongside loose, porous zones and needle-like, plate-like reaction products morphologically consistent with carbonate-bearing AFm-type phases such as monocarboaluminate and hemicarboaluminate, though the authors caution that SEM alone cannot confirm phase identity.

Then came the durability trials, framed in an unusual but physically precise vocabulary. Rather than the conventional labels of wet-dry and freeze-thaw cycling, the researchers speak of liquid-vapor and liquid-solid phase cycling, emphasizing what the pore water itself is doing. In the liquid-vapor test, specimens spent 8 hours immersed in water, 8 hours drying naturally, and 8 hours in a 75-degree-Celsius oven, repeating the absorption-evaporation cycle up to 30 times. In the liquid-solid test, a rapid freeze-thaw apparatus swung the specimen core temperature between minus 35 and plus 20 degrees Celsius every 5 hours, forcing pore water to freeze, redistribute, and melt again and again. The results diverged sharply. After 30 liquid-vapor cycles, silica fume-modified concrete lost only 9.3 percent of its compressive strength, dropping from 27.9 to 25.3 megapascals, while the unmodified control lost 18.8 percent. Freezing proved far more brutal: after 15 liquid-solid cycles, the unmodified and limestone-modified specimens had lost roughly 70 and 67 percent of their strength, and by 30 cycles both had collapsed beyond the point of valid testing.

The survivors told the most important story. Sodium silicate-modified concrete, which had not been the best performer in the wet-dry regime, proved the champion of freeze-thaw resistance, retaining the highest residual strength, 9.7 megapascals after 30 cycles, and enough structural integrity to keep testing. Post-cycling nanoindentation after 15 cycles confirmed that the damage was concentrated precisely where the team expected: the aggregate region barely changed, the paste weakened moderately, and the ITZ deteriorated most severely. Silica fume’s interface lost only 3.8 percent of its minimum modulus under liquid-vapor cycling, while sodium silicate’s interface retained both the highest absolute modulus and the smallest relative loss, 24.8 percent, under liquid-solid cycling. The lesson is that different coatings build different kinds of interfacial quality, and the best choice depends on the environment the concrete will face.

The mechanistic explanation ties the whole picture together. Surface modification does not eliminate water-induced deterioration; it delays its initiation, localization, and propagation within the ITZ. Silica fume’s fine particles plug the small voids where moisture redistribution would otherwise nucleate microcracks, making it ideal for hot, drying climates with repeated wetting. Sodium silicate, supplying soluble silicate species into an alkaline local environment, appears to foster a more continuous, product-rich interfacial fabric that can distribute the internal pressures generated by ice formation and delay debonding and crack coalescence, making it the better choice for cold regions. Limestone powder, with its more heterogeneous product distribution, offered the least protection against either regime. The authors note that water-migration pathways were inferred from combined macroscopic, microscopic, and nanoindentation evidence rather than directly measured, and that local alkalinity changes and individual reaction products were not quantified.

What makes this work resonate beyond the laboratory is its double dividend: it converts an environmental liability into infrastructure material while simultaneously making that material tougher than anyone expected. Because the binder itself is built from calcined coal gangue, fly ash, and desulfurization gypsum, an entire concrete could one day be assembled almost entirely from industrial byproducts, with nothing more exotic than sodium silicate, silica fume, or ground limestone standing between a weak interface and a durable one. For coal regions searching for a future after mining, and for a construction sector under pressure to cut its carbon and resource footprint, the humble act of coating a waste rock particle before it enters a mixer may prove to be one of the most consequential steps in sustainable materials engineering.

Subject of Research: Surface modification of coal gangue aggregate to strengthen the interfacial transition zone in coal-based solid-waste concrete

Article Title: Surface modified coal gangue aggregate in coal-based solid-waste concrete: ITZ strengthening and resistance to water phase-transition cycling

Article References: Wang, Y., Yang, Y., Yu, C., Li, R., Chang, J., & Zhang, T. (2026). Surface modified coal gangue aggregate in coal-based solid-waste concrete: ITZ strengthening and resistance to water phase-transition cycling. Case Studies in Construction Materials, 25, Article e06572. https://doi.org/10.1016/j.cscm.2026.e06572

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06572

Keywords: coal gangue, concrete, interfacial transition zone, surface modification, sodium silicate, silica fume, limestone powder, freeze-thaw resistance, solid waste recycling, nanoindentation, sustainable construction, coal-based binder

The review’s methodology tells its own story. De-Giorgio and Benedetti searched PubMed, Scopus, and Web of Science without date restrictions, combining AFM-related terms with post-mortem and autopsy keywords, and screened references manually to catch anything the databases missed. Despite the breadth of the search, only five original research articles met their strict criteria of focusing on human post-mortem materials with forensic relevance. That number is striking. AFM has been embraced enthusiastically in materials science, nanotechnology, biology, and clinical medicine for decades, yet its application to the tissues of the deceased remains in its infancy. The five qualifying studies concentrated on just four substrates: bone, skeletal muscle, tendinous tissue, and hair. This scarcity, the authors argue, reflects a combination of high instrumentation costs, small sample sizes, and substantial methodological heterogeneity that has kept the field fragmented.

Bone emerges as the most scientifically mature substrate in the review. Building on earlier animal studies that mapped elastic and inelastic deformation behavior and visualized the lacunar-canalicular network with exceptional precision, researchers turned to human autopsy samples to probe age-related changes in bone composition. In one key investigation, Milovanovic and colleagues characterized mineral grain size in bone harvested from the lateral femoral neck of two groups of women: young women aged 20 to 40 and elderly women aged 73 to 94. The older cohort exhibited larger and more heterogeneous mineral grains, a structural condition associated with reduced mechanical resistance. Crucially, chemical analysis of calcium and phosphorus levels revealed no significant differences between the groups, ruling out a major confounder and reinforcing the validity of the purely structural observations.

A follow-up study translated those structural differences into mechanical terms using AFM-based nanoindentation. The technique works by applying a controlled force to the sample surface and recording the corresponding force-distance curves, from which local mechanical properties can be computed with precision. The results showed that the differences in mineral grain size between young and elderly women translated into distinct elastic behaviors, with significantly reduced elasticity in the elderly group, an effect closely linked to higher fracture susceptibility. Although limited by sample size, the work demonstrated a reproducible methodological framework that the review’s authors believe could be extended to contexts far more directly relevant to forensic investigation, including the characterization of fracture margins in cases of suspected trauma.

It is in forensic traumatology that the review’s most provocative proposals appear. AFM topography and force mapping can quantify nanoscale roughness, microcrack patterns, and local stiffness gradients along fracture edges, capabilities that could support the differentiation between perimortem trauma, injuries inflicted around the time of death, and post-mortem damage that occurred afterward. One high-impact translational scenario involves cardiopulmonary resuscitation. CPR is well recognized to generate rib fracture patterns that can complicate post-mortem interpretation, sometimes mimicking injuries inflicted by an assailant. AFM could add objective surface and mechanical descriptors to complement macroscopic evaluation, radiology, and conventional microscopy, helping pathologists distinguish resuscitation artifacts from thoracic fractures unrelated to resuscitative maneuvers. In an era when CPR-related rib injuries are common and medico-legal disputes over their origin are frequent, such a tool could prove decisive.

Bone is also highly informative in cases of thermal exposure, including fires and explosions. Experimental work has shown that heating produces progressive physicochemical and structural modifications of bone mineral: crystallite parameters begin to change at temperatures of 500 degrees Celsius and above, while marked crystallite growth and recrystallization become prominent at higher temperatures, commonly reported around 700 degrees Celsius and beyond, with downstream effects on the stability and fragility of calcined remains. Post-mortem computed tomography, or PMCT, has already proven valuable in assessing burned victims, including the recognition of typical heat-related changes and the differentiation of heat-related fractures from traumatic ones. The review proposes a correlative framework in which PMCT provides non-destructive, case-level documentation of fracture patterns, ATR-FTIR spectroscopy and X-ray diffraction characterize temperature-related mineral and matrix transformations, and AFM targets selected regions for nanoscale topographic and nanomechanical mapping. The open question is whether thermal overprinting modifies or preserves the nanoscale features relevant to forensic interpretation, and AFM is positioned to answer it.

Soft tissue tells a different story, one in which water plays an unexpectedly large role. Studies on human iliotibial band samples investigated how variations in water content influence the mechanical properties of post-mortem soft tissues, and the findings were clear: lower water content increases the elastic modulus of the tissue. This has direct implications for anyone designing experiments on post-mortem soft tissues, since hydration status must be controlled for or at least reported. With specific regard to estimating the post-mortem interval, the elapsed time since death and one of the central questions in forensic practice, De-Giorgio and colleagues performed a preliminary investigation on skeletal muscle samples collected at different post-mortem intervals, applying AFM-based measurements of the Young’s modulus and hysteresis, the latter reflecting energy dissipation during loading cycles. Their results indicated that hysteresis is less influenced by inter-individual variability than the elastic modulus, making it a parameter worth prioritizing in future PMI-focused studies. This matters because traditional PMI methods, which rely on qualitative assessment of livor mortis, rigor mortis, and algor mortis, are fundamentally constrained by the examiner’s subjective evaluation and by intrinsic factors including age, sex, muscle mass, and ambient temperature.

Hair, remarkably durable and easy to sample, offers a third window into the post-mortem nanoworld. Mansilla and colleagues compared hair samples from contemporary autopsies with those from archaeological mummies to examine nanostructural cellular features. Compared with modern hair, the mummy samples exhibited a depletion of fatty acids and a reduction in the regularity of the cuticular scale pattern, although the scales themselves remained remarkably preserved even after centuries. The review’s authors suggest extending this analytical approach by comparing mummy hair across different historical periods and geographic regions, potentially revealing correlations between long-term environmental exposure and nanostructural hair alterations. Such a comparative framework could eventually help investigators assess whether remains are consistent with a claimed historical context or with a more recent death.

Perhaps the most forward-looking sections of the review concern substrates that have barely been touched in forensic settings. Skin, which has been extensively investigated with AFM in dermatological research on the epidermis and dermis, remains underexplored in forensic pathology, despite the fact that establishing wound vitality and age is often critical for medico-legal reconstruction and remains methodologically challenging. AFM-derived parameters such as surface topography, local stiffness mapping, and viscoelastic signatures could be investigated for their association with the post-trauma interval, provided that major confounders including hydration status, sampling site, and fixation protocol are explicitly controlled. The authors also point to dried bloodstains, where experimental studies have used AFM to estimate stain age by tracking changes in the mechanical properties of red blood cells over time, with subsequent work showing that substrate type, whether glass, metal, or ceramic, significantly affects the mechanical signature. Gunshot residue analysis represents another avenue, since AFM has already been applied to high-resolution characterization of GSR particle morphology and size distribution, with evidence that particle size distributions may vary as a function of shooting distance. Extending such analyses to peri-wound skin at entry and exit sites could reveal reproducible patterns related to muzzle-to-target distance and ammunition type. Even the subtle electrical current mark seen in electrocution victims, currently assessed mainly through histopathology and scanning electron microscopy with energy-dispersive X-ray analysis, could yield additional microfeatures to AFM’s nanomechanical mapping.

The review is candid about the obstacles standing between these visions and courtroom reality. The evidence base is constrained by small sample sizes, high instrumentation costs, and methodological heterogeneity spanning differences in sampling, preparation, AFM operational modes, and reporting standards. To support AFM as a reliable forensic tool, and ultimately strengthen its potential admissibility in court, the authors call for robust statistical reporting including appropriate summary measures, dispersion indices, and explicit assessment of reproducibility and measurement uncertainty. They also advocate multicentric research designs to increase sample representativeness and distribute financial and logistical burdens, along with standardized post-mortem imaging biobanks built on harmonized acquisition protocols to facilitate cross-study comparison and accelerate the integration of AFM-based metrics into forensic science. Bone, skeletal muscle, and hair remain the most practical starting points, being generally accessible at autopsy and collectable with limited manipulation. If those foundations are laid, the nanoscale may soon become a routine crime scene, one measured not in meters but in nanometers.

Subject of Research: Applications of atomic force microscopy to human post-mortem tissues in forensic medicine

Article Title: Atomic force microscopy in human post-mortem samples: current applications and future directions

Article References: De-Giorgio, F., & Benedetti, B. (2026). Atomic force microscopy in human post-mortem samples: current applications and future directions. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-03976-x

Image Credits: AI Generated

DOI: 10.1007/s00414-026-03976-x

Keywords: atomic force microscopy, forensic science, post-mortem interval, forensic pathology, bone nanomechanics, nanoindentation, skeletal muscle, mummified hair, thermal bone alteration, wound age estimation, gunshot residue, legal medicine

Muscle is a hierarchical composite material, and that architecture is the key to the new framework. At the smallest level sit myofibrils, the contractile protein threads built from repeating sarcomeres, each containing Z-disks, A-bands, and H-bands. Myofibrils bundle together into muscle fibers, wrapped in a thin collagenous sheath called the endomysium. Fibers in turn group into bundles encased in a thicker connective tissue layer, the perimysium. Connective tissues form a continuous network that reinforces the muscle and transmits force between fibers and bundles. Because each level contributes to the whole, the team hypothesized that macroscopic texture could be quantitatively predicted if the mechanical properties of the microscopic components and their volume fractions were known.

Testing that hypothesis required measuring mechanics at scales where no conventional test can operate. The researchers turned to atomic force microscopy, or AFM, a technique in which an ultrasharp silicon nitride tip, with a radius of just a few nanometers, is pressed against a sample while the force of contact is recorded. Fitting the resulting force-indentation curves with the Derjaguin-Muller-Toporov contact model, which accounts for both elastic deformation and van der Waals adhesion, yields the local Young’s modulus. The team applied this to myofibrils isolated from pork tenderloin, beef tenderloin, and chicken breast, as well as to extracted endomysium and perimysium, measuring both dried and hydrated samples. Hydration mattered enormously: dried myofibrils showed moduli in the gigapascal range, while wet samples dropped by one to two orders of magnitude into the tens of megapascals, a reminder that data from dried biological materials can have limited relevance to real food.

The nanoscale maps revealed striking patterns. In raw myofibrils, stiffness followed a consistent spatial order across all three species: the Z-disk was stiffest, the A-band intermediate, and the H-band softest, echoing earlier AFM studies on rabbit and rat muscle. Species differences were also clear. In the hydrated raw state, pork myofibrils were the stiffest at roughly 50 megapascals, beef followed at about 47, and chicken was softest at around 34. Cooking reshuffled the dried-state landscape, erasing the species-specific sarcomere structures as proteins denatured and aggregated, but the wet cooked myofibrils preserved the same hierarchy, with pork highest at about 75 megapascals and chicken lowest at about 45. The collagenous membranes told their own story: the perimysium was consistently slightly stiffer than the endomysium, and both stiffened after cooking, likely through heat-induced collagen denaturation and aggregation.

With the microscopic inputs in hand, the team built a two-level analytical model based on the classical Reuss series scheme from composite mechanics. Under transverse compression, a single muscle fiber was treated as myofibrils embedded in an endomysium matrix, and a fiber bundle as equivalent fibers in series with the perimysium. The effective modulus of each level is the volume-fraction-weighted combination of its phases, with the phase fractions measured from scanning electron microscope images of fiber cross-sections. Running the numbers, the model predicted bundle moduli that ranked pork highest, beef intermediate, and chicken lowest, and predicted a significant increase after cooking, trends that mirror the myofibril data feeding into it. Notably, the predicted bundle modulus correlated strongly with the myofibril and endomysium moduli but not with the perimysium modulus, suggesting that in this low-connective-tissue muscle system, the bundle stiffness is governed primarily by the fibers themselves.

The validation step came from macroscopic compression tests on cubes of raw and cooked meat using a texture analyzer, with the compression axis carefully aligned perpendicular to the muscle fibers to match the orientation of the nanoscale measurements. The stress-strain curves were strongly nonlinear, stiffening as strain increased, so the team fitted them with two constitutive models. A combined logarithmic-polynomial hyperelastic model, originally developed for liver tissue, captured the general shape but showed systematic deviations, particularly for chicken. A logistic model, adapted from work on passive spinal muscle mechanics, performed far better, with coefficients of determination above 0.997 for every sample. Its parameters carried clear physical meaning: an initial modulus reflecting the relaxed response of the microscopic components, a hardening increment describing nonlinear stiffening, a hardening rate, and a critical strain at which stiffening accelerates.

The correlation analysis tied the scales together. The logistic model’s initial modulus correlated strongly with the linear modulus measured from the first five percent of strain, and both correlated with the multiscale model’s predicted bundle modulus and, through it, with the myofibril and endomysium properties. In other words, the initial stiffness of a piece of meat is largely written into its myofibrils. The nonlinear parameters told a different story. Beef showed the largest hardening increment, which the authors attribute to its denser network of mature collagen crosslinks and the pronounced nonlinear hardening behavior of the perimysium observed in the AFM force curves, potentially explaining why beef is chewier than pork or chicken. Bound water content correlated positively with the initial stiffness parameters, while free water correlated negatively with the hardening rate, hinting that water acts as a lubricant that smooths the structural response under compression.

The authors are careful about scope. The AFM-derived moduli of the isolated connective tissues represent effective properties of collagen-rich fractions rather than absolute in situ values, and the constitutive models describe rate-independent behavior at a single loading speed rather than the full viscoelastic response of muscle. Validation was performed on three relatively lean, low-connective-tissue muscles, so extending the framework to collagen-rich cuts such as tendon-laden muscles remains future work. The link between micro- and macroscale is also framed as a parametric correlation rather than a direct numerical equivalence, with microscopic stiffness serving as the physical foundation for macroscopic structural stiffness rather than substituting for it one-to-one.

Even with those caveats, the implications are broad. The study delivers a quantitative, bottom-up route from nanoscale protein mechanics to the texture a consumer actually perceives, clarifying which hierarchical structures dominate which aspects of the mechanical response. For the booming plant-based meat industry, where replicating the fibrous architecture and anisotropic mechanics of real muscle remains the central challenge, the framework offers something like a design blueprint: a way to specify the stiffness and volume fraction of the protein and matrix phases needed to hit a target bite. More broadly, it demonstrates that with enough care at the nanoscale, even something as familiar and complex as the texture of dinner can be reduced to physics you can measure, model, and ultimately engineer.

Subject of Research: Multiscale mechanical modeling linking AFM nanomechanics of myofibrils and connective tissue to the macroscopic compressive texture of meat

Article Title: Predicting the compression mechanical properties of muscle from microscale indentation mechanics using multiscale mechanical models

Article References: Zhao, C., Jiang, R., Zhang, Z., Jia, J., Nishinari, K., & Yang, N. (2026). Predicting the compression mechanical properties of muscle from microscale indentation mechanics using multiscale mechanical models. Current Research in Food Science, Article 101577. https://doi.org/10.1016/j.crfs.2026.101577

Image Credits: AI Generated

DOI: 10.1016/j.crfs.2026.101577

Keywords: meat texture, atomic force microscopy, myofibrils, multiscale modeling, connective tissue, food science, compression mechanics, plant-based meat, collagen, constitutive models, Reuss model, nanoindentation