Now, a team of researchers at the Federal University of Alagoas in Brazil has developed a bifunctional fluorescent film that can monitor healing through pH changes while simultaneously acting as an antioxidant agent in the treatment of wounds. The study, published in Frontiers in Carbon, focuses on films based on polyvinyl alcohol (PVA) and carbon dots (CDs) derived from two very different sources: lemon peel bagasse, a food industry waste product, and ortho-phenylenediamine, a synthetic aromatic compound. The work represents a rare systematic attempt to combine pH sensing and antioxidant therapy in a single bioactive dressing, addressing a gap the authors note is still uncommon in wound research.

Carbon dots are luminescent carbon nanoparticles smaller than 10 nanometers with a spherical morphology, featuring a graphitic core and a surface decorated with functional groups characteristic of the precursor materials used during synthesis. They exhibit excellent optical properties, including fluorescence in the visible spectrum, good dispersion in water, biocompatibility, photo-stability, low toxicity, antimicrobial activity and low-cost synthesis. These properties, combined with their non-invasiveness and good sensitivity, have made them attractive candidates for biological fluorescent sensors. However, when exposed to different pH environments, individual carbon dots typically exhibit only one emission band, and gradations in the wavelength of maximum emission change with low clarity, making pH detection difficult to visualize reliably.

To overcome this limitation, the researchers turned to ratiometric fluorescent sensing, a strategy that employs dual emission bands at different wavelengths. Rather than relying on a single fluorescence intensity, a ratiometric sensor provides a correlation from the ratios of fluorescence intensities at different wavelengths, which minimizes background interferences and improves sensitivity, precision and detection. The team synthesized two types of carbon dots: CD-L, derived from Tahiti lemon bagasse via a rapid microwave method, and CD-oPD, derived from ortho-phenylenediamine via a hydrothermal reaction. CD-L emits in the blue region with a maximum centered at 450 nanometers, while CD-oPD emits in the yellowish-green region with a maximum centered at 550 nanometers. Both exhibited excitation-independent emission, a feature associated with uniform sizes, molecular states and passivated surface defects.

Transmission electron microscopy revealed that both CD-L and CD-oPD exhibited spherical graphitic morphology with uniform size dispersion, with average diameters of 2.54 ± 0.44 nanometers and 2.64 ± 0.60 nanometers respectively. The interplanar distances typical of graphitic structure were observed at 0.21 and 0.24 nanometers, corresponding to the (100) diffraction plane for CD-L and CD-oPD respectively. Fourier transform infrared spectroscopy identified the main functional groups: broad O-H stretching bands around 3,445 and 3,330 cm⁻¹ for CD-L and CD-oPD respectively, C-H vibrations between 2,970 and 2,700 cm⁻¹, and for CD-L, bands suggestive of C=O, C=C and C-N groups associated with oxygenated functionalities, a polyaromatic graphitic core and surface-functionalizing nitrogen groups. For CD-oPD, peaks characteristic of aromatic C-N and N-H angular deformation were observed at 1,330 and 780 cm⁻¹ respectively.

The photostability of both carbon dots was assessed using photoluminescence spectroscopy, with fluorescence intensity recorded under UV lamp excitation for 60 minutes continuously. The results remained practically unchanged during the analyzed period, with variations in the fluorescence signal of less than 10 percent, confirming their suitability for sustained sensing applications. When solutions of CD-L and CD-oPD were mixed in an optimized ratio, the researchers observed a dual emission with bands centered at 450 and 550 nanometers, consistent with the individual spectra of each carbon dot. The resulting ratiometric system, named CD-L/oPD, showed a high sensitivity for detecting pH in the range of 5 to 10, an interval suitable for monitoring the wound healing process.

The analytical response of the CD-L/oPD system to pH variation was investigated using photoluminescence spectroscopy. The ratio of fluorescence intensities at 460 and 550 nanometers, I460/I550, as a function of pH value, fit well to a sigmoidal curve in the pH range of 5 to 10, with a relationship having an r² of 0.992. This variation in the I460/I550 ratio allows for the visualization of a color change from yellowish-green to green with increasing pH, a gradient that can be seen with the naked eye. By contrast, the individual carbon dots showed only linear functions in the pH range from 6 to 10, with CD-L demonstrating a blue emission with no perceptible change to the naked eye and CD-oPD revealing a consistent yellow emission except at pH 9, where a pale yellowish-green color was observed. The protonation and deprotonation of oxygenated groups on the carbon dot surfaces explains the fluorescence modulation: after pH 7, these groups are deprotonated, causing a decrease in fluorescence intensity.

The researchers then incorporated the carbon dots into a PVA matrix to produce flexible, transparent fluorescent films. Under natural light, the films were colorless for CD-L-F and yellowish for CD-oPD-F and CD-L/oPD-F. Under UV light, the characteristic blue emission of CD-L was observed for CD-L-F, and yellow and yellowish-green for CD-oPD and CD-L/oPD films respectively. The maximum emission wavelengths of the films shifted toward the blue compared to the carbon dots in solution, a phenomenon the researchers attribute to the formation of hydrogen bonds between the PVA and the surface functional groups of the carbon dots when the nanoparticles are stabilized in the polymer. When applied to an ex vivo pig skin model sprayed with different pH solutions ranging from 5 to 9, the CD-L/oPD-F film was more efficient at visually discriminating color in relation to pH changes than films prepared from the individual carbon dots, displaying a significant change from greenish-yellow to green as pH increased from 5 to 9.

Swelling tests conducted in Britton-Robinson buffer at pH 5, 7 and 9 revealed that the degree of swelling of the films increased with pH and time, reaching equilibrium in 60 minutes. The minimum and maximum swelling percentages at pH 5, 7 and 9 were 47.5 to 59.5, 59.0 to 75.5 and 97.5 to 153.5 respectively. These values were suitable to maintain the shape and uniform edges of the films after the swelling tests. The pH-dependent swelling response is attributed to ionizable functional groups of the PVA (hydroxyl) and the carbon dots (hydroxyl and carboxyl), which promote electrostatic repulsion and increase interactions with water as pH increases, expanding the film and creating a greater surface area available for the diffusion of water molecules.

Beyond pH sensing, the carbon dots demonstrated significant antioxidant capacity against reactive oxygen species, which are formed during normal cellular respiration but in excess contribute to the development and progression of diseases resulting from oxidative stress. In the inflammatory phase of wound healing, an excess of ROS is produced and is considered the main factor hindering skin regeneration, causing oxidative structural modifications in lipids, DNA and proteins that lead to necrosis at the wound site. The IC50 values for CD-L and CD-oPD were 56.7 and 39.5 μg mL⁻¹ in the DPPH radical inhibition assay, and 25.1 and 63.4 μg mL⁻¹ in the hypochlorous acid scavenging assay respectively. CD-L exhibited higher antioxidant capacity against physiologically relevant reactive species such as superoxide anion and HOCl, while CD-oPD showed no elimination capacity against superoxide anion but demonstrated greater potential for capturing the DPPH radical. These values compare favorably with carbon dots derived from beet juice, which exhibited an IC50 of 231.7 μg mL⁻¹ against DPPH, and clove-derived carbon dots, which showed an IC50 of 57 μg mL⁻¹ against the same radical.

Biocompatibility was evaluated using MTT viability assays with human non-tumoral skin fibroblast HFF-1 cells, which showed a cell survival rate of over 80 percent for both carbon dots up to a concentration of 1,000 μg mL⁻¹, corroborating the relatively negligible cytotoxicity of the nanoparticles in non-transformed human fibroblasts. Cells treated with triton-X (1 percent) were used as a control for reduced cell viability, showing only 28 percent viable cells. The authors suggest that the developed films can act in a bifunctional way, monitoring healing through pH changes and acting as an antioxidant agent in the treatment of wounds, offering a real-time, in situ measurement of pH value and redox status. While carbon dots have been explored as fluorescent pH sensors, systematic studies aimed at combining different properties to offer both monitoring and treatment of wound healing remain rare, and this work seeks to address that gap by combining the use of carbon dots in film form to act as an antioxidant agent, protective barrier and colorimetric pH sensor with a view to their use as bioactive dressings.

Subject of Research: Materials Science

Article Title: Carbon dots-based fluorescent films to act as a potential antioxidant agent and pH ratiometric sensor for skin applications

Article References: Da Silva, L. E., Araujo, A. P. D. L., Almeida, J. H., de Vasconcelos, L. B. O. D., Silva, M. D. O., Lima, D. J. P., Viana, R. D. S., Ferro, J. N. D. S., Goulart, M. O. F., Xavier, J. A., & Barbosa, C. D. A. E. S. (2023). Carbon dots-based fluorescent films to act as a potential antioxidant agent and pH ratiometric sensor for skin applications. Frontiers in Carbon, 2, Article 1300811. https://doi.org/10.3389/frcrb.2023.1300811

Image Credits: AI Generated

DOI: 10.3389/frcrb.2023.1300811

Keywords: carbon dots, wound healing, pH sensor, antioxidant, polyvinyl alcohol, fluorescent films, reactive oxygen species, smart dressings, nanotechnology, biomaterials, Carbon, dots-based

The team, led by Devyani Gupta, Akash Chandra, Jagruti M. Patil and Karla P. Mercado-Shekhar, systematically fabricated seventy-five phantoms from 10 percent PVA hydrogel, varying aluminum oxide from 0 to 10 percent by weight and two cryoprotectants, ethylene glycol and propylene glycol, from 0 to 20 percent by volume. For each formulation they measured density, longitudinal sound speed, acoustic attenuation, shear modulus and viscosity, and examined the microstructure with scanning electron microscopy. The question was deceptively simple: when you add an ingredient to tune one property, what happens to everything else?

Aluminum oxide has long been treated as a one-trick additive. Its job is to absorb and scatter ultrasound, mimicking the way real soft tissue attenuates sound waves as they travel through the body. The study confirmed that it does this beautifully. Attenuation climbed from 0.12 to 0.54 dB/cm/MHz across the concentration range, with a striking linear correlation of r = 0.98. But the surprise came when the researchers turned to shear wave viscoelastography, a technique that sends ripples of shear waves through a material and reads its stiffness from how fast those waves disperse. The shear modulus of the phantoms rose from 3.05 to 5.32 kilopascals, a 1.7-fold increase, correlated with aluminum oxide concentration at r = 0.79. Density rose in parallel from 1.03 to 1.14 g/cm3.

The physical explanation is elegant. Rigid ceramic particles embedded in a soft polymer matrix cannot deform when a shear wave passes through. They restrict the conformational freedom of the surrounding PVA chains, so the network as a whole requires more force to deform, registering as a stiffer material. Meanwhile, the longitudinal sound speed, hovering between 1576 and 1583 m/s, and the viscosity, between 1.58 and 2.15 Pa s, remained essentially unchanged. So a phantom designer who adds aluminum oxide to match tissue attenuation is, whether they realize it or not, also manufacturing a stiffer phantom, a confounding variable that could bias elastography benchmarks in ways nobody has previously accounted for.

The cryoprotectant story turned out to be stranger still. Ethylene glycol and propylene glycol are added to PVA because, during the freeze-thaw cycling that gives PVA hydrogels their strength, they suppress the growth of large ice crystals that would otherwise leave a porous, inhomogeneous structure. Electron microscopy confirmed the effect dramatically: without cryoprotectant, the hydrogel network was highly porous; with either glycol, even at modest concentrations, it became dense and non-porous, and stayed that way across the entire range.

But the mechanical response of the gels did not follow a simple trend. With ethylene glycol, the shear modulus fell from 6.94 kPa in the cryoprotectant-free gel to a minimum of 3.81 kPa at 15 percent concentration, and then rebounded sharply to 8.01 kPa at 20 percent, the stiffest formulation in the entire study. Propylene glycol behaved differently: the modulus decreased from the baseline through 10 percent and then plateaued at roughly 4 kPa through 20 percent. The authors attribute the initial softening to plasticization, with glycol molecules wedging themselves between PVA chains, breaking interchain hydrogen bonds and increasing free volume. The sudden stiffening at high ethylene glycol concentrations, by contrast, may mark a threshold at which the small glycol molecule, at 62.07 g/mol versus 76.09 g/mol for propylene glycol, draws water away from the polymer chains, allowing them to re-establish strong cross-links or form microcrystallites. The bulkier propylene glycol molecule apparently cannot pack efficiently enough to trigger this re-crystallization.

The acoustic measurements told a parallel tale. Sound speed rose almost perfectly linearly with cryoprotectant concentration, from 1535 to 1643 m/s for ethylene glycol and 1535 to 1666 m/s for propylene glycol, both with correlation coefficients of 0.99. Propylene glycol edged out its smaller cousin at the top end, possibly because its extra methyl group produces a tighter local arrangement within the hydrogel pores. Attenuation also increased with concentration for both glycols, from about 0.27 to 0.40 dB/cm/MHz, an effect the researchers link to the denser hydrogen-bonded fluid network that forms as the glycol fraction rises, increasing frictional losses for propagating waves.

Viscosity, the other half of the viscoelastic picture, showed a simpler pattern. Adding either cryoprotectant significantly lowered viscosity relative to the baseline, but beyond 5 percent concentration the values plateaued, remaining statistically indistinguishable from 5 to 20 percent. This saturation makes molecular sense: the first doses of glycol structure free water within the hydrogel pores through hydrogen bonding, but once the primary hydration sites are saturated, additional glycol simply pools into the already-structured fluid phase without changing the macroscopic resistance to shear flow. The takeaway for phantom builders is that the choice between ethylene glycol and propylene glycol, and the exact concentration, matter far more than a perusal of the standard literature would suggest.

Why does all this matter beyond the materials lab? Shear wave viscoelastography is an active clinical research area for assessing liver fibrosis, breast lesions and thyroid nodules, and recent work has shown that treating inherently viscoelastic tissues as purely elastic introduces substantial errors in modulus estimates. Phantoms sit at the foundation of this enterprise: they are how new reconstruction algorithms are validated, how machines are calibrated, and how measurements are compared across hospitals and studies. If the additive used to tune attenuation simultaneously shifts the shear modulus, or if the cryoprotectant chosen to smooth the microstructure also drives a nonlinear swing in stiffness, then phantom-based benchmarks inherit biases that propagate all the way to the clinic.

The Gandhinagar team frames its findings as a step toward standardizing phantom fabrication protocols and controlling confounding variables, and the contribution is genuinely novel in scope. Prior work had examined only the presence or absence of ethylene glycol, and propylene glycol had been used almost exclusively for sound-speed tuning without anyone checking its downstream effects. This study is the first direct head-to-head comparison of the two cryoprotectants under identical fabrication and measurement conditions, and the first to report aluminum oxide’s effect on PVA phantom mechanics. The authors acknowledge limitations: they did not test ethylene glycol above 20 percent, where the stiffening reversal might continue or reverse again; they did not assess long-term stability beyond two days; and they used the widely adopted Kelvin-Voigt model rather than exploring alternative rheological frameworks. Future work, they suggest, will incorporate shear wave attenuation corrections and monitor phantoms over six to twelve months. For now, the message to the field is clear: in tissue-mimicking materials, nothing acts alone, and every recipe must be read as a whole.

Subject of Research: Effects of aluminum oxide and cryoprotectant additives on the acoustic and viscoelastic properties of polyvinyl alcohol tissue-mimicking phantoms for shear wave viscoelastography

Article Title: Characterization of tissue-mimicking polyvinyl alcohol phantoms for shear wave viscoelastography: effects of aluminum oxide and cryoprotectant concentration

Article References: Gupta, D., Chandra, A., Patil, J. M., & Mercado-Shekhar, K. P. (2026). Characterization of tissue-mimicking polyvinyl alcohol phantoms for shear wave viscoelastography: effects of aluminum oxide and cryoprotectant concentration. Frontiers in Acoustics, 4, Article 1920457. https://doi.org/10.3389/facou.2026.1920457

Image Credits: AI Generated

DOI: 10.3389/facou.2026.1920457

Keywords: tissue-mimicking phantom, polyvinyl alcohol, aluminum oxide, ethylene glycol, propylene glycol, acoustic attenuation, shear wave viscoelastography, ultrasound elastography, viscoelasticity, cryoprotectant, sound speed, hydrogel

The target of the investigation was calcium silicate hydrate, or C-S-H, the binding phase that gives cement its strength. C-S-H is a layered material: stiff silicate chains form sheets that are stacked and held together by water molecules and calcium ions. That layered architecture is both a blessing and a curse. Within the sheets, the silicon-oxygen framework is extremely rigid, but between the sheets the material is comparatively soft and prone to sliding and separation. This anisotropy means that C-S-H — and therefore concrete — behaves very differently depending on the direction of the load, and it is precisely at these vulnerable interlayer regions that vibration damage tends to begin.

To probe how polymers could shore up these weak zones, the team built realistic atomistic models of C-S-H with a calcium-to-silicon ratio of 1.67, matching ordinary Portland cement, and inserted three representative polymers into the interlayer spaces: polyethylene (PE), polyvinyl alcohol (PVA), and polybutadiene (PB). These three were chosen deliberately because they differ in one crucial chemical respect. PE and PB are essentially nonpolar hydrocarbon chains, while PVA is decorated with abundant hydroxyl groups — the same -OH chemistry that makes water sticky. The polymer content was kept between roughly 1 and 5 percent by weight, consistent with what is used in real damping-modified concretes.

The simulations themselves were ambitious. Using the LAMMPS package with the ClayFF and CVFF force fields, the researchers first calibrated their model against known experimental and computational values, confirming that the tensile strength, elastic modulus, and shear modulus of their C-S-H matched earlier studies. They then subjected both pristine and polymer-modified C-S-H to two kinds of cyclic shear loading: constant strain-rate cycling and sinusoidal loading inspired by dynamic mechanical analysis, the standard laboratory technique for measuring viscoelastic damping. Each condition ran for 72 full loading cycles, with simulations lasting up to 46 nanoseconds — an enormous investment of computational time at the atomic scale.

The mechanical results were encouraging but nuanced. Adding polymers barely changed the tensile strength of C-S-H along its strong direction, and left shear strength along the stiff XY plane essentially untouched, because that direction is governed by the intrinsic silicate framework. But along the weak interlayer direction, the story changed dramatically. Polymer chains acted as molecular bridges spanning adjacent C-S-H sheets, raising shear strength in the XZ direction and — critically — providing residual strength after failure. When unmodified C-S-H was pulled apart along its weak axis, it fractured completely; when polymer was present, the broken pieces remained tethered together, delaying catastrophic failure and increasing the material’s ductility and toughness. Dosage mattered too: around 2.5 to 2.7 percent by weight gave the best tensile reinforcement, while 4.9 to 5.3 percent maximized shear enhancement.

The atomic-scale analysis explained why. Radial distribution functions showed that polymers sitting on the (010) surface of C-S-H readily form hydrogen bonds with interlayer water molecules at distances of roughly 2 to 3 angstroms, whereas polymers on the (001) surface form almost none. Hydrogen bond counting during deformation revealed that these bonds are the workhorses of interlayer cohesion: under tension along the weak direction, the hydrogen bond network collapses, but under shear it largely survives, allowing energy to be dissipated gradually through sliding and rearrangement rather than sudden breakage. Among the three polymers, PVA formed by far the most hydrogen bonds with C-S-H, thanks to its hydroxyl-rich chemistry, giving it the strongest interfacial grip.

When the team turned to damping — the heart of the study — the findings became genuinely striking. Under cyclic shear, plain C-S-H showed equivalent viscous damping of about 0.099 along the XY direction and 0.096 along XZ. After polymer modification, damping along the stiff XY direction rose only modestly, but along the weak XZ direction it jumped substantially: PE increased the loss factor by about 10.1 percent, PB by 11.3 percent, and PVA by 13.7 percent. Even more interesting, polymer modification flipped the anisotropy. Before modification, C-S-H dissipated more energy along its strong plane; after modification, the formerly weak interface became the better energy-dissipating interface. In effect, the polymers converted concrete’s structural liability into a functional asset.

The viscoelastic measurements reinforced this picture. Under sinusoidal loading, both the storage modulus, which measures elastic energy storage, and the loss modulus, which measures energy converted to heat, increased after polymer modification — with PVA again showing the largest gains. The non-zero phase shift between applied strain and resulting stress confirmed that C-S-H is genuinely viscoelastic, and the polymers widened that phase lag, particularly along the interlayer direction. The mechanism is elegant: hydrogen-bonded polymer bridges increase interlayer friction and enable controlled structural rearrangement during each cycle, so vibrational energy that would otherwise drive crack growth is instead bled away as heat, cycle after cycle.

The implications for infrastructure are considerable. A concrete that can dissipate vibration without sacrificing strength could extend the service life of bridges, tunnels, seismic-resistant buildings, and industrial facilities, while reducing maintenance costs and material consumption. The study is careful to acknowledge its limits: each simulation condition was run once, the nanosecond-scale loading frequencies far exceed real structural frequencies, and features like aggregates and heterogeneous hydration products are absent from the models. The authors frame their results as molecular-level guidance rather than engineering predictions, and call for experimental dynamic mechanical analysis and multiscale modeling to validate the mechanism at full scale. Still, the core insight stands: by choosing polymers with the right hydrogen-bonding chemistry — PVA chief among them — and orienting them within cement’s weakest layers, engineers may one day design concrete that doesn’t just resist vibration, but quietly swallows it.

Subject of Research: Molecular mechanisms of polymer-induced damping enhancement in calcium silicate hydrate

Article Title: Hydrogen-bond-mediated damping enhancement in polymer-modified calcium silicate hydrate

Article References: Liu, Y., Zaoui, A., & Sekkal, W. (2026). Hydrogen-bond-mediated damping enhancement in polymer-modified calcium silicate hydrate. Results in Engineering, 32, Article 113328. https://doi.org/10.1016/j.rineng.2026.113328

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.113328

Keywords: calcium silicate hydrate, molecular dynamics, hydrogen bonds, polyvinyl alcohol, damping, cement, viscoelasticity, concrete, interlayer sliding, energy dissipation, C-S-H, infrastructure

A team of pharmaceutical scientists in India has now developed a thin, flexible film loaded with amixicile, a next-generation antimicrobial, designed to be placed directly into the diseased gum pocket. The work, published in Discover Chemistry, describes how the researchers combined amixicile with two film-forming polymers, the natural polysaccharide pullulan and the synthetic, water-soluble polymer polyvinyl alcohol, to create a locally applied treatment for periodontitis. Amixicile is a derivative of the antiparasitic drug nitazoxanide and works through an unusual mechanism: it inhibits pyruvate-ferredoxin oxidoreductase, or PFOR, a key enzyme in the energy metabolism of anaerobic bacteria. By binding to thiamine pyrophosphate, a cofactor the enzyme depends on, amixicile prevents pyruvate from binding, blocking the formation of acetyl-CoA and carbon dioxide and thereby starving anaerobic pathogens of energy. Crucially, every oral Treponema species studied so far relies on PFOR, making amixicile a particularly promising candidate against periodontal pathogens, while its high selectivity for anaerobic organisms keeps it relatively non-toxic to host tissues.

The choice of polymers was equally deliberate. Pullulan, a fermentation product of the fungus Aureobasidium pullulans, is non-ionic, bio-erodible and biocompatible, with outstanding film-forming ability; it is already used in commercial oral care films sold internationally under the Listerine brand. Its many hydroxyl groups make it highly water-soluble, so it absorbs water, swells and breaks down, helping entrapped drug molecules diffuse out. Polyvinyl alcohol complements this by adding mechanical strength through intermolecular hydrogen bonding, improving the film’s elasticity, wettability and swelling behavior. Together, the two polymers form a matrix that is strong enough to be handled and inserted into a gum pocket yet dissolves quickly enough to release its payload. The films themselves were made by solvent casting: the polymers were dissolved in water, amixicile was stirred into the homogeneous blend, and the solution was cast into petri plates and dried in a hot air oven at 80 degrees Celsius before being trimmed into two-by-two-centimeter squares.

Before formulating, the team established how much drug is actually needed to stop microbial growth. Using a broth dilution method, they determined that the minimum inhibitory concentration of amixicile against both Pseudomonas aeruginosa and Candida albicans was 20 micrograms per milliliter. The minimum bactericidal concentration against Pseudomonas aeruginosa and the minimum fungicidal concentration against Candida albicans were both 25 micrograms per milliliter. The choice of test organisms reflects the complex ecology of periodontal pockets: Candida albicans is the most prevalent fungus in both healthy and diseased oral cavities and has been shown to facilitate invasion of gingival epithelial cells by Porphyromonas gingivalis, while Pseudomonas aeruginosa, though not a primary periodontal pathogen, can thrive in the low-oxygen niches of periodontal pockets, forming biofilms and secreting virulence factors such as phenazines and pyocyanin that sustain inflammation and tissue destruction.

To optimize the formulation rather than rely on trial and error, the researchers employed a central composite design, a statistical approach that systematically varies the concentrations of pullulan and polyvinyl alcohol and models their effects on two critical quality attributes: in-vitro drug release and tensile strength. Nine formulations were produced and evaluated. Drug content across the batches ranged from 87.7 to 97.4 percent, indicating that amixicile was evenly dispersed throughout the films. Drug release over five minutes ranged from about 81.8 to 95.2 percent, with formulations A1 and A6 performing best. The regression analysis revealed that both polymers increased drug release, but pullulan’s linear coefficient, 4.80, was nearly three times that of polyvinyl alcohol, 1.69, confirming that the hydrophilic polysaccharide was the dominant driver of dissolution. A low interaction coefficient showed the two polymers acted largely through their individual effects rather than synergistically on release.

Tensile strength told a complementary story. The strongest film, batch A1, withstood 12.8 newtons per square centimeter, a result attributed to high polymer concentrations producing dense chain entanglement and extensive hydrogen bonding. But excessive rigidity can compromise elasticity and patient comfort during periodontal application, so the strongest film was not necessarily the best. Batches with low polymer content, A2 through A5, ranged from just 1.02 to 5.23 newtons per square centimeter, reflecting weak matrix cohesion. Batch A6, with moderate polymer levels, achieved 10.78 newtons per square centimeter, striking what the authors describe as the ideal balance between structural stability and flexibility. The statistical models for both responses were validated by analysis of variance, with model F-values of 119.88 for drug release and 22.51 for tensile strength, and prediction errors for the optimized batch of only 0.41 percent for release and 2.13 percent for mechanical strength.

The optimized formulation, containing 300 milligrams of pullulan and 200 milligrams of polyvinyl alcohol, was then put through a full battery of characterization tests. The yellow film was uniform and smooth, with an average thickness of 0.06 millimeters, a weight of 0.0125 grams, and a folding endurance of 200 folds, indicating robust mechanical integrity. Its pH of 6 falls within the natural range of the oral cavity during gingival infections, minimizing irritation risk, and it disintegrated completely in about one minute, enabling rapid drug release. In-vitro diffusion through a cellophane membrane reached 78.6 percent over 70 minutes, notably longer than the five-minute release window, because only one side of the film contacted the membrane. When tested against fresh sheep gingival mucosa, ex-vivo diffusion reached 65.1 percent, with a steady-state flux of 0.93 micrograms per square centimeter per minute, about 16 percent lower than the in-vitro value, a reduction the researchers attribute to the additional diffusional and partitioning resistance of biological tissue.

Perhaps the most striking results came from the antimicrobial testing. Using an agar-well diffusion assay, the optimized film produced a zone of inhibition of 35 millimeters against Pseudomonas aeruginosa and 28 millimeters against Candida albicans. A plain pullulan film without drug showed much smaller zones, 18 and 22 millimeters respectively, meaning the drug-loaded film enlarged the inhibition zone by 94.4 percent against the bacterium and 27.3 percent against the fungus, differences that were statistically significant. The particularly large effect against Pseudomonas aeruginosa makes mechanistic sense, since that organism depends directly on the PFOR pathway that amixicile disables, whereas the eukaryotic fungus is affected through a less direct route. These findings suggest the film could suppress both the bacterial and fungal contributors to periodontal infection at the site where they do their damage.

The broader significance of this work lies in its approach to a stubborn clinical problem. Deep periodontal pockets, those exceeding four millimeters, are often inaccessible to thorough cleaning because of tooth structure, which is precisely why localized delivery systems that place antimicrobials directly at the infection site, prolonging drug contact time while limiting systemic exposure, have attracted so much research attention. A dissolvable film that releases over 95 percent of its drug within minutes, then sustains diffusion for over an hour, could offer clinicians a non-invasive, easy-to-insert option that avoids the resistance risks of systemic antibiotics. The authors are careful to note that the road to the clinic is not yet complete: preclinical periodontal efficacy testing, mucosal safety and toxicity studies, bioadhesion and residence time measurements, microbiological efficacy against clinically relevant periodontal organisms, and eventually clinical trials will all be required before therapeutic use can be established. Still, the convergence of a mechanistically novel antimicrobial, well-characterized biocompatible polymers, and rigorous statistical optimization makes this amixicile film a compelling candidate in the fight against a disease poised to affect billions.

Subject of Research: Development of an amixicile-loaded pullulan and polyvinyl alcohol composite film for localized drug delivery in periodontitis treatment

Article Title: Amixicile loaded polyvinyl alcohol and pullulan composite film for localized periodontal treatment

Article References: Kandekar, U., Davkare, P., Pandit, A., Chaudhari, P., Chavan, M., Sayare, A., & Kolhe, R. (2026). Amixicile loaded polyvinyl alcohol and pullulan composite film for localized periodontal treatment. Discover Chemistry, 3(1), Article 573. https://doi.org/10.1007/s44371-026-01011-x

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01011-x

Keywords: amixicile, periodontitis, pullulan, polyvinyl alcohol, drug delivery film, PFOR inhibitor, antimicrobial, periodontal pocket, solvent casting, central composite design, Pseudomonas aeruginosa, Candida albicans

Gallium-based liquid metals such as eutectic gallium–indium (EGaIn) have long been viewed as the most promising intrinsically deformable conductors. They combine metallic-level conductivity, on the order of a million siemens per meter, with liquid-like flow at room temperature, allowing them to endure extreme strain without fracturing. Yet their practical adoption has been hampered by two stubborn problems. In air, gallium rapidly forms a self-limiting oxide shell roughly three nanometers thick that stabilizes droplet shape but acts as an electrical insulator, blocking electron transport between neighboring particles. At the same time, the metal’s very high surface tension, near 600 millinewtons per meter, makes it difficult to wet and pattern uniformly on soft elastomeric substrates. As a result, most liquid metal inks are electrically dead when deposited and require a separate thermal, mechanical, laser, or chemical activation step to rupture the oxide and establish conductive pathways.

The new work tackles both obstacles at once by wrapping each liquid metal particle in an ultrathin polymer shell and then exploiting the physics of the spray process itself. Bulk EGaIn is fractured into microscale droplets by tip sonication in a 5 weight percent aqueous PVA solution, run at 20 percent amplitude in pulsed mode to prevent overheating. PVA chains hydrogen-bond to the freshly formed gallium oxide surface, lowering particle surface energy and improving wettability. A centrifugation step removes free, unbound polymer, leaving particles with a controlled PVA layer estimated at 7 to 10 nanometers thick atop the 3 to 5 nanometer native oxide. Transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed this layered structure, with the carbon signal of the polymer conformally wrapping the oxygen-rich oxide shell. The team emphasizes that the PVA is retained after deposition, where it serves as a fusion mediator and adhesive bridge rather than an insulating barrier.

Getting the shell thickness right proved decisive. Particles carrying an excessively thick PVA coating, produced before the centrifuge refinement, showed improved wettability but could not make direct particle-to-particle contact, yielding films roughly eightfold less conductive than the optimized formulation. The refined PmLMP films reached an electrical conductivity of approximately 1.5 × 10^6 siemens per meter immediately after spraying. Zeta potential measurements help explain why: pristine particles carry a strongly negative surface charge of about −70 millivolts, creating an electrostatic barrier that keeps neighbors apart, while PVA modification reduces this to roughly −38 millivolts, allowing hydrodynamic forces during printing to push particles into intimate contact. Density functional theory calculations, using isopropanol as a model for the PVA repeat unit and hydroxylated gallium oxide as a surface model, supported the feasibility of a moderate hydrogen bond at the interface, with a counterpoise-corrected interaction energy of −23.2 kilojoules per mole.

The heart of the innovation is a synergistic mechano-fluidic mechanism that unfolds in a single deposition event. First, high-velocity impact of aerosolized particles delivers enough mechanical stress to rupture the oxide–polymer shell, exposing fresh metallic surfaces that coalesce on contact. Atomic force microscopy nanoindentation measured a yield force of 266.08 nanonewtons per particle, only slightly above the 200 to 250 nanonewtons reported for bare oxide-shelled particles, confirming that the ultrathin PVA layer does not meaningfully suppress rupturability. X-ray photoelectron spectroscopy provided chemical corroboration: screen-printed control films showed only oxidized gallium signals, whereas spray-printed films revealed distinct indium peaks and metallic Ga^0 features, consistent with shell rupture exposing the metallic core. The researchers estimate a critical impact velocity of only about 4 meters per second, well below the particle speeds achieved at the optimized 30 psi spray pressure.

Second and third, the drying process itself consolidates the network. Because the ink uses a binary solvent of deionized water and ethanol in a 3:1 volume ratio, a surface-tension gradient arises within each deposited droplet, driving Marangoni convection. High-speed imaging of fluorescent tracer particles and microparticle image velocimetry showed flow velocities up to 50 times faster, averaging a 22.4-fold increase, compared with a single-solvent system. These vortical flows redistribute particles, counteract gravitational sedimentation, and wedge smaller particles into the voids between larger ones, creating nanoscale point contacts where capillary stress concentrates. The team’s capillary-bridge model predicts a lateral force of roughly 79 nanonewtons at each interparticle meniscus, and under an illustrative contact radius of about 11 nanometers this corresponds to local stresses near 200 megapascals, plausibly sufficient to rupture residual shells. Transmission electron microscopy captured metallic neck formation at particle contacts, and the binary-solvent formulation delivered a threefold conductivity enhancement over the water-only control.

Process optimization revealed how sensitively the mechanism depends on spray parameters. Ultrasonic amplitudes above 50 percent, despite producing smaller particles, introduced enough energy to generate gallium oxide and hydroxide byproducts that interfered with coalescence, so 20 percent amplitude proved optimal. Conductivity saturated at carrier-gas pressures above 30 psi, where kinetic energy reliably exceeds the rupture threshold. Working distance mattered too: at 6 centimeters, air resistance dissipated too much particle energy, while at 3 centimeters the balance of partial solvent evaporation and retained impact energy enabled efficient fusion. The resulting process patterned conductive traces with nominal linewidths down to 50 micrometers and coated areas larger than 20 by 20 square centimeters, and a batch-printed 4 by 4 array showed an average conductivity of 1.55 × 10^6 siemens per meter with limited pixel-to-pixel variation.

Electromechanical testing underscored the practical payoff. Under monotonic tension, PmLMP traces retained electrical continuity beyond 200 percent strain and up to 800 percent, with relative resistance rising only gradually to about 2.8, whereas unmodified particle films lost continuity through droplet beading and over-coated films fractured near 100 percent strain. Cyclic testing at 100 percent strain over 50,000 seconds, roughly 1,400 stretch-release cycles, showed reproducible resistance modulation with limited drift. Integrated light-emitting diodes stayed illuminated through twisting, 100 percent stretching, and bending, and star-shaped LED arrays printed on table-tennis balls, tennis balls, and basketballs remained operational, demonstrating conformability across curvatures. On nonpolar substrates such as PDMS and Ecoflex, an oxygen-plasma pretreatment improved trace uniformity by increasing surface polarity for hydrogen bonding.

The team then pushed the platform toward real devices. Because the printed interconnects are conductive on arrival, standard components, including a microcontroller, resistor, and LEDs, could be pick-and-placed directly onto as-printed flexible circuits that remained functional after folding. A flexible wound-healing patch carrying 640-nanometer red LEDs, driven at 10 hertz and encapsulated in Ecoflex, accelerated macroscopic wound closure relative to untreated controls over seven days in a murine full-thickness excisional wound model. Large-area conductive patterns were printed directly onto textile banners, and the same platform, paired with a LiCl-hydrogel skin interface, served as a wearable electromyography and electrocardiography system. Wireless EMG signals transmitted over Bluetooth Low Energy controlled a remote-controlled vehicle in real time, while custom software visualized ECG waveforms and computed heart rate. Together, these demonstrations sketch a manufacturing route in which liquid metal circuits emerge from an ordinary airbrush already alive with current, opening possibilities for wearable healthcare, bio-integrated electronics, and human-interactive devices that no longer wait for a sintering oven to switch them on.

Subject of Research: Post-treatment-free spray deposition of PVA-modified liquid metal particles for soft and wearable electronics

Article Title: Synergistic Mechano‐Fluidic Self‐Fusion of Poly(Vinyl Alcohol)‐Modified Liquid‐Metal Particles for Post‐Treatment‐Free Soft Electronics

Article References: Yook, K.-Y., Kim, S., Kim, C., Kang, M., Lee, Y., Kim, M., Park, K., Han, S. Y., Cho, S.-W., Lee, G.-H., Son, K., Jang, H., Kim, T. Y., & Seo, J. (2026). Synergistic Mechano‐Fluidic Self‐Fusion of Poly(Vinyl Alcohol)‐Modified Liquid‐Metal Particles for Post‐Treatment‐Free Soft Electronics. Advanced Science, Article e78062. https://doi.org/10.1002/advs.78062

Image Credits: AI Generated

DOI: 10.1002/advs.78062

Keywords: liquid metal, soft electronics, spray printing, EGaIn, poly(vinyl alcohol), self-fusion, wearable sensors, Marangoni convection, capillary forces, stretchable conductors, electromyography, wound healing

The motivation is straightforward. Pork is one of the world’s most consumed meats, and projections cited by the Organization for Economic Co-operation and Development suggest global consumption will reach 129 million metric tons by 2032, accounting for roughly a third of projected growth in total meat consumption. Yet pork’s high lipid and protein content, stored in the humid microclimate of a sealed package, makes it an ideal substrate for microbial spoilage. Consumers still judge freshness by color and odor, subjective cues that vary from person to person, while conventional laboratory tests for spoilage are costly, slow, and require trained personnel and elaborate sample preparation.

Smart labels offer a way around that bottleneck. As meat spoils, microbes and enzymes release volatile compounds that raise the pH inside the package. Freshness indicators exploit this chemistry by embedding pH-sensitive pigments that visibly change color as the atmosphere shifts. Synthetic pigments work well but raise health and environmental concerns, so researchers have turned to natural dyes. Curcumin, the polyphenol that gives turmeric its golden hue, is yellow under acidic conditions and turns orange-red when alkaline. Alizarin, an anthraquinone from madder roots, goes from light yellow in acid to bluish-purple in base. Used alone, however, each pigment responds over a narrow pH window with limited color contrast.

The research team, led by Bingcan Liu, Siling Zhang, and Zeyu Wu of Hefei University of Technology, solved both the pigment problem and a materials problem at once. They blended curcumin and alizarin at six different mass ratios, from pure curcumin to pure alizarin, and electrospun each mixture into nanofibers made of polyvinyl alcohol (PVA) blended with zein, a hydrophobic corn protein. Electrospinning draws a charged polymer jet from a Taylor cone under a 16-kilovolt electric field; as the jet whips and stretches toward the collector, it dries into solid fibers with enormous surface area and porosity, ideal for gas sensing. Crucially, the process involves no high temperatures, so the delicate pigments survive intact.

The polymer blend was the key to durability. Pure PVA films dissolve in humid conditions because of their abundant hydroxyl groups, which would be fatal for a label inside a moist meat package. By mixing in zein, rich in nonpolar amino acids, the researchers produced fibers averaging roughly 76 to 120 nanometers in diameter, far finer than the 347-nanometer fibers of pure PVA. Scanning electron microscopy showed smooth, continuous, well-fused fibers, evidence of good compatibility between the two polymers. Fourier transform infrared spectroscopy confirmed hydrogen bonding across the network, with characteristic zein amide bands appearing alongside PVA’s hydroxyl and carbon-oxygen stretches.

Water resistance improved dramatically. Pure PVA films showed 100 percent water solubility and a 100 percent swelling index, meaning they disintegrated completely in water. With zein and pigments added, water solubility fell to between 31 and 35 percent, moisture content dropped from 7.58 percent to as low as 4.5 percent, and the swelling index fell by about 35 percent. The hydrophobic protein shields PVA’s polar groups from water, while hydrogen bonds between the pigments and the matrix occupy binding sites that water molecules would otherwise attack. The films also held their color during ten days of storage at both 4 and 25 degrees Celsius, with total color differences remaining below 3, well under the threshold of 5 that untrained observers can perceive.

Sensitivity testing sealed squares of each film in a chamber with controlled vapors of ammonia, dimethylamine, and trimethylamine, the signature gases of meat decay, at concentrations from 1 to 40 parts per million. The mixed-pigment films outperformed single-pigment versions on both ends of the spectrum. Films containing both dyes detected ammonia and dimethylamine at just 1 part per million, five times more sensitive than the alizarin-only film, while mixed formulations responded to trimethylamine at 10 parts per million, better than curcumin alone. The three intermediate blends, with curcumin-to-alizarin ratios of 4:1, 3:2, and 2:3, showed the most pronounced and varied color changes, because the paired pigments broaden the pH response range and multiply the distinguishable hues.

The decisive test came with real pork. The team affixed a circular array of six indicator films inside the lids of glass containers holding about 60 grams each of chilled pork tenderloin, then refrigerated the samples at 4 degrees Celsius for six days. Daily measurements of total volatile basic nitrogen, the regulatory benchmark for meat spoilage, tracked the meat’s decline: below 10 milligrams per 100 grams on day one, between 10 and 15 on days two and three, and 15.54 on day four, crossing the Chinese national limit of 15. Lipid oxidation, measured by the thiobarbituric acid assay, rose from 0.16 to 0.52 milligrams per kilogram, and pH climbed from 5.96 to 6.58 as protein-degrading bacteria took over from glycogen fermenters.

The array’s color output mirrored this trajectory almost perfectly. The films drifted from light yellow through reddish-brown to purple as spoilage progressed, and a composite chromatic parameter calculated from all six films jumped sharply on day four, exactly when the meat crossed into the spoiled category. Pearson correlation coefficients between the color parameter and the three chemical spoilage markers were strikingly high: 0.98 for total volatile basic nitrogen, 0.98 for lipid oxidation, and 0.95 for pH. Single-pigment labels, by contrast, often lagged or produced changes too subtle to notice, which is precisely why the array design matters. By reading several films together, the system converts a fuzzy qualitative signal into a reliable three-tier grading of fresh, less fresh, and spoiled.

The researchers describe the platform as eco-friendly, low-cost, and scalable, and the ingredients support that claim: biodegradable PVA, an abundant food-grade corn protein, and non-toxic dyes already common in the food supply. Because the label works inside ordinary packaging and needs no instrument beyond the human eye, it could plausibly move from the laboratory to supermarket shelves and home refrigerators. The work also points toward broader applications, since the same dual-pigment, dual-polymer strategy could be tuned for fish, shrimp, beef, or any protein-rich food whose spoilage chemistry raises the local pH. For a food system that loses enormous value to spoilage and foodborne illness alike, a label that quietly turns from yellow to purple may prove one of the simplest and most consequential safety tools yet devised.

Subject of Research: A pH-sensitive curcumin-alizarin electrospun nanofiber array for colorimetric monitoring of pork freshness

Article Title: Synergistic PVA/zein electrospun nanofiber array with curcumin-alizarin: a water-resistant, sensitive colorimetric platform for graded pork freshness monitoring

Article References: Liu, B., Zhang, S., Geng, H., Hu, C., Zhou, A., & Wu, Z. (2026). Synergistic PVA/zein electrospun nanofiber array with curcumin-alizarin: a water-resistant, sensitive colorimetric platform for graded pork freshness monitoring. Food Chemistry: X, Article 104591. https://doi.org/10.1016/j.fochx.2026.104591

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104591

Keywords: electrospinning, nanofibers, curcumin, alizarin, smart packaging, pork freshness, food safety, pH indicator, volatile amines, zein, polyvinyl alcohol, colorimetric sensor

The material, developed by Zhi Lei, Daohai Zhang and colleagues, is built from two inexpensive and environmentally friendly ingredients: polyvinyl alcohol, a widely used water-soluble polymer, and gelatin, a natural biomass-derived protein. The researchers combined them into a semi-interpenetrating network in which the two polymer chains entangle during gelation and are further crosslinked by hydrogen bonds between abundant amino and hydroxyl groups. That molecular architecture produces a three-dimensional porous scaffold with high water content, and the same hydrophilic functional groups allow the gel to adhere to skin, paper, glass and metal through hydrogen bonding and intermolecular forces. Into this matrix the team dispersed composite nanoparticles made of carbon nanotubes decorated with ZIF-67, a cobalt-based metal-organic framework in which cobalt ions are coordinated by 2-methylimidazole ligands into a highly ordered porous crystal.

Each component of the hybrid filler plays a distinct role. Carbon nanotubes are lightweight and highly electrically conductive, so they raise the conductivity of the hydrogel dramatically, from 0.34 siemens per meter for the pristine polymer blend to 0.62 siemens per meter, an increase of 82.35 percent. ZIF-67, meanwhile, contributes cobalt centers that absorb electromagnetic waves, giving the composite dual loss mechanisms: dielectric loss from the conductive carbon network and magnetic loss from the cobalt ions. Together, the two phases dissipate incoming electromagnetic energy as heat rather than letting it pass through or bounce off. The porous hydrogel scaffold adds a third layer of defense, because its three-dimensional architecture provides anchoring sites for the nanoparticles and forces penetrating waves to undergo multiple internal reflections, each of which bleeds away more energy.

The synthesis relied on three complementary techniques. First, an in situ growth method deposited rhombic dodecahedral ZIF-67 crystals directly onto the surfaces of carboxylated multi-walled carbon nanotubes, with cobalt nitrate and nanotubes dispersed in methanol at controlled mass ratios and then added to a 2-methylimidazole solution under stirring for 24 hours. Second, a one-pot method dispersed the resulting CNTs@ZIF-67 particles uniformly into the aqueous PVA-gelatin precursor under ultrasonication. Third, cyclic freeze-thaw treatment physically crosslinked the polymers into a stable gel without any toxic chemical crosslinkers. Scanning electron microscopy confirmed that ZIF-67 had grown on the nanotubes and revealed how the fillers reshaped the gel’s internal pores.

Perhaps the most intriguing structural finding concerns electrostatics. When ZIF-67 alone was added, cobalt ions attracted electron-rich groups on the polymer chains, causing chain segments to bunch together and collapsing the gel’s three-dimensional network into a smoother, denser morphology. Carbon nanotubes alone infiltrated the pores and shrank them. But the combined CNTs@ZIF-67 particles produced hydrogels with more numerous and larger pores than either single filler. The researchers attribute this to an electrostatic confinement effect: oxygen anions on the nanotube surfaces neutralize the positive charge of the cobalt ions, weakening the electrostatic interactions between the composite and the polymer matrix and preserving the porous architecture that is so important for wave attenuation.

Spectroscopic analysis backed up the picture. X-ray diffraction peaks of the synthesized ZIF-67 matched the standard reference pattern at all expected crystal planes, indicating a complete lattice, while the hydrogels showed narrowed diffraction peaks consistent with grain-size changes induced by the cobalt-containing filler. Fourier transform infrared spectra showed no new functional groups after doping, meaning the nanoparticles disperse physically within the polymer framework rather than forming new chemical bonds. X-ray photoelectron spectroscopy, however, revealed subtle electronic interactions: the cobalt 2p binding energies shifted upward in the doped gels, suggesting that hydroxyl and carboxyl groups coordinate with cobalt ions and redistribute electron density at the interface.

Mechanically, the composite gel proved remarkably robust. The pristine PVA-gelatin hydrogel withstood compressive stresses of 18.75 megapascals at 71.07 percent strain; the shielding version reached 19.67 megapascals at 66.33 percent strain, with its compressive modulus rising from 38.1 to 41.8 kilopascals as the fillers constrained chain mobility and increased crosslinking density. A cylinder of the composite hydrogel just half a centimeter in diameter could lift a 200-gram weight without fracturing, and the material stayed firmly attached to paper, iron rods and glass rods for extended periods. Differential scanning calorimetry showed the additives did not disturb the gel’s crystallization behavior, and water content remained high at 88.99 percent, with water absorption of 265.92 percent, so the shielding function came without sacrificing the hydration and flexibility that make hydrogels attractive for wearables.

The electromagnetic results were the study’s centerpiece. Measured with a vector network analyzer across the X-band from 8.2 to 12.4 gigahertz, the plain hydrogel achieved an average shielding effectiveness of 14.70 decibels. The optimized composite, designated PGZC1, reached 33.32 plus or minus 1.67 decibels, a 126.7 percent improvement that comfortably exceeds the 20-decibel threshold generally considered effective shielding. Analysis of the reflection, absorption and transmission coefficients showed near-zero transmission and absorption dominating over reflection, confirming that the material neutralizes waves by soaking up their energy rather than bouncing them back toward other devices, a crucial distinction for crowded electronic environments. Conductivity of the optimized gel measured 0.512 plus or minus 0.026 siemens per meter.

Intriguingly, more nanotubes were not always better. When the researchers increased the carbon nanotube proportion in the CNTs@ZIF-67 filler, shielding effectiveness progressively declined. The explanation lies in agglomeration: nanotubes have enormous surface area and strong van der Waals attraction, so at higher loadings they clump together, disrupting the synergistic interplay between the carbon and the ZIF-67 phase and damaging the gel’s porous structure, which reduces the surface area and active sites available for wave scattering. The finding underscores a recurring lesson in composite design, that uniform dispersion at modest loadings can outperform brute-force addition of conductive filler.

The researchers propose a clear shielding mechanism that ties the observations together. The PVA-gelatin network forms the structural scaffold, while well-dispersed CNTs@ZIF-67 particles build a conductive network and help generate relatively independent, complete spherical pores. When a wave strikes the surface, part is reflected and part penetrates, losing energy as it crosses the conductive walls; reflected components bounce between wall layers, attenuating further with each pass. Because absorption dominates, the energy ultimately dissipates as heat within the material. The authors suggest the gel’s combination of high shielding, toughness, adhesion, water retention and processability positions it for flexible electronics, wearable devices and stretchable sensors, offering a green, low-cost route to protecting both devices and people from the electromagnetic clutter of modern technology.

Subject of Research: CNTs@ZIF-67 composite nanoparticles enhancing electromagnetic interference shielding in tough PVA-gelatin organic hydrogels

Article Title: CNTs@ZIF-67 conductive composite nanoparticles enhance the electromagnetic shielding performance of tough organic hydrogels

Article References: Lei, Z., Zhang, D., Hu, Y., Zhou, T., Diao, K., Liu, D., Song, A., Zou, K., & Qin, S. (2026). CNTs@ZIF-67 conductive composite nanoparticles enhance the electromagnetic shielding performance of tough organic hydrogels. iScience, 29(11), Article 114635. https://doi.org/10.1016/j.isci.2026.114635

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.114635

Keywords: electromagnetic interference shielding, hydrogel, carbon nanotubes, ZIF-67, metal-organic framework, polyvinyl alcohol, gelatin, X-band, wearable electronics, dielectric loss, magnetic loss, conductive composites

Crystal violet is not merely a cosmetic nuisance. The triarylmethane dye, widely used in textile printing, paper production, and even as a biological stain, is toxic to aquatic life and suspected of harmful effects in humans, which is why researchers worldwide are racing to find cheap, sustainable ways to capture it before it reaches rivers and groundwater. Adsorption, the process by which dye molecules cling to the surface of a solid material, remains one of the most practical removal strategies, but the performance of any adsorbent depends heavily on how much accessible surface it offers.

That is where electrospinning comes in. The technique applies a high voltage to a droplet of polymer solution, stretching it into a whip-like jet that whips through the air, solvent evaporating along the way, until it lands as fibers with diameters measured in nanometers. Because these fibers pack enormous surface area and high porosity into a small mass of material, they expose a vast number of adsorption sites to the surrounding water. The Iranian team exploited this by blending polyvinyl alcohol, a water-friendly synthetic polymer, with gum arabic, a natural exudate from acacia trees prized for its biocompatibility and abundance of functional groups.

The twist in this study is the addition of carbon dots, nanoscale carbon-based particles that have attracted enormous interest for their fluorescence, low toxicity, and ease of green synthesis. Embedded within the electrospun nanofiber matrix, the carbon dots contribute additional interaction sites and functional chemistry that boost the composite’s ability to bind positively charged crystal violet molecules. The researchers prepared the composite solution and spun it directly into the final adsorbent, avoiding harsh chemicals and keeping the entire fabrication route aligned with green chemistry principles.

To confirm that the material was what they intended, the authors subjected it to a battery of characterization techniques. Fourier transform infrared spectroscopy mapped the chemical bonds and functional groups present in the fibers, verifying that the polymer, gum, and carbon dot components were integrated. X-ray diffraction probed the internal structure, while scanning electron microscopy revealed the fibrous morphology, showing the continuous, porous network that gives the material its high surface area. Energy dispersive X-ray analysis confirmed the elemental composition, and transmission electron microscopy allowed the team to visualize the nanoscale architecture, including the distribution of carbon dots within the fibers.

With the adsorbent in hand, the group systematically tested how well it captured crystal violet from water and, just as importantly, how the process worked. Adsorption kinetics were evaluated using three classical models: pseudo-first-order, pseudo-second-order, and intraparticle diffusion. The data aligned best with the pseudo-second-order model, a result with real mechanistic meaning, since it indicates that the rate-limiting step involves chemical interactions, such as electron sharing or electrostatic attraction, between the dye molecules and the binding sites on the fiber surface, rather than simple physical deposition.

The equilibrium behavior told a complementary story. When the team fitted their adsorption data to the Langmuir, Freundlich, and Temkin isotherm models, the Langmuir model provided the best description. That outcome implies that crystal violet molecules occupy a finite set of energetically equivalent sites on the nanofiber surface, forming at most a single molecular layer, and that once a site is filled it can no longer accept another dye molecule. Such monolayer adsorption on a uniform surface is exactly what one hopes for in a well-behaved, predictable adsorbent, making it easier to design treatment systems around the material.

Thermodynamic analysis added further insight into the driving forces at play. The results showed that the adsorption process is spontaneous and exothermic, meaning it proceeds willingly at the tested conditions and releases heat as the dye binds. An exothermic signature typically points to physical and electrostatic interactions dominating the uptake and suggests that lower temperatures favor adsorption, information that matters when engineers consider real-world wastewater streams whose temperatures vary with season and location.

Perhaps the most encouraging finding for practical deployment came from the reusability tests. Many promising adsorbents falter in regeneration, losing capacity after a handful of cycles as their binding sites clog or their structure degrades. The carbon dot-embedded PVA/gum arabic nanofibers, by contrast, demonstrated high recoverability with no considerable loss in adsorption performance over six consecutive adsorption-desorption cycles. That durability addresses one of the biggest economic hurdles for nanomaterial-based water treatment, since a sorbent that must be replaced after every use quickly becomes prohibitively expensive.

The study sits within a broader surge of interest in biopolymer-based electrospun adsorbents, from gum-based fibers explored for food packaging to hydrogels and aerogels built from chitosan, alginate, and cellulose for capturing dyes, heavy metals, and pharmaceuticals. What distinguishes this work is the combination of three benign ingredients, a scalable fiber fabrication method, and rigorous kinetic, isotherm, and thermodynamic modeling that together demonstrate a coherent, sustainable package. As textile industries in water-stressed regions face tightening discharge rules, materials like these green nanofibers could offer a route to cleaner effluent that does not trade one environmental problem for another, turning tree sap, a common polymer, and carbon nanodots into an effective filter for one of the dye industry’s most persistent pollutants.

Subject of Research: Green carbon dot-embedded electrospun PVA/gum arabic nanofibers for adsorptive removal of crystal violet dye from water

Article Title: Green carbon dot–embedded Electrospun PVA/gum arabic nanofibers for efficient crystal violet removal from aqueous media

Article References: Safaei, A., Giyahban, F., & Ebrahimzadeh, H. (2026). Green carbon dot–embedded Electrospun PVA/gum arabic nanofibers for efficient crystal violet removal from aqueous media. Environmental Science and Pollution Research, 33(30), 15784-15798. https://doi.org/10.1007/s11356-026-38234-5

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38234-5

Keywords: carbon dots, electrospun nanofibers, gum arabic, polyvinyl alcohol, crystal violet, dye removal, adsorption, wastewater treatment, Langmuir isotherm, pseudo-second-order kinetics, green adsorbent, water purification

The study, published in the journal Advanced Composites and Hybrid Materials, was led by Ki-Hyun Ryu and Sungju Lee of the Korea Institute of Science and Technology, together with colleagues across several KIST research centers. Their central insight is deceptively simple: instead of trying to push ions into a densely packed nanotube fiber after the fact, why not build molecular-scale breathing room into the material from the very beginning? The answer they arrived at relies on a thermodynamically driven co-assembly process borrowed from the world of liquid crystals, a field more often associated with display screens than with supercapacitors.

To understand why the problem matters, it helps to picture what happens inside a conventional carbon nanotube fiber. Individual nanotubes, each essentially a rolled-up sheet of graphene a few nanometers wide, are drawn together into bundles, and those bundles are packed into a fiber with inter-bundle spacing measured at the molecular scale. This ultra-dense arrangement maximizes the contact between tubes, which is exactly what you want for load transfer and for electrons hopping from one tube to the next. But for electrochemical applications, the picture inverts. Ions from an electrolyte can only access the outermost surfaces of the fiber; the deep internal channels between bundles remain inaccessible, so the enormous theoretical surface area of the nanotubes goes largely unused. Materials scientists have long described this as a packing-accessibility trade-off, and it has been a persistent bottleneck in translating the extraordinary properties of individual nanotubes into practical devices.

The Korean team’s strategy attacks the problem at the molecular level using soft poly(vinyl alcohol), or PVA, chains. PVA is a hydrophilic, water-soluble polymer, and the researchers exploited its strong non-covalent adsorption onto carbon nanotube surfaces to intercalate the polymer chains directly into the nanotube bundles during fiber formation. Because the process occurs during a lyotropic liquid crystalline co-assembly stage, the rigid nanotubes retain the high axial alignment that is essential for efficient electron transport along the fiber, while the flexible polymer chains wedge themselves between the bundles and hold the channels open. The researchers describe the resulting architecture as unlocked, in the sense that the interstitial channels that would normally collapse into dense packing are instead molecularly secured at a controlled spacing.

The thermodynamics of this intercalation are worth appreciating. When long, flexible polymer chains are confined between rigid nanotubes, they lose some conformational entropy, but the strong adsorption energy between the polymer and the carbon surface compensates for that loss, driving the hybrid structure to self-assemble spontaneously. Once in place, the entropic relaxation of the soft chains, their tendency to coil and spread, effectively props open the interstitial channels without any external scaffolding, template, or post-processing step. This bottom-up approach stands in contrast to more common strategies that graft bulky functional groups onto nanotube walls or hybridize the fibers with additional active materials, both of which can disrupt the intrinsic structure of the nanotubes or add complexity and cost to manufacturing.

The benefits of the unlocked architecture extend beyond simple spacing. Carbon nanotube surfaces are inherently hydrophobic, which impedes wetting by aqueous electrolytes and further limits ion access. The intercalated PVA chains, being hydrophilic, impart wettability to the composite fiber, so electrolyte ions are not only given physical pathways into the interior but are also chemically encouraged to penetrate. In effect, the polymer performs double duty: it acts as a molecular spacer that maintains the channels, and it converts the fiber’s internal environment from one that repels electrolytes to one that welcomes them. The dormant internal volume of the fiber, previously inaccessible, becomes an active participant in electrochemical processes.

The quantitative evidence for this internal activation is striking. When the researchers measured the electrochemical performance of their composite fibers, they found an 11.2-fold enhancement in specific capacitance compared with pristine carbon nanotube fibers. Specific capacitance is a direct measure of how much charge a material can store per unit mass, and an improvement of more than an order of magnitude indicates that ions are genuinely reaching the deep core of the fiber rather than merely decorating its surface. The composite fibers also showed superior rate performance, meaning they retained much of their charge-storage capability even when charged and discharged rapidly. Rate capability is a sensitive probe of ion diffusion resistance: if ions had to fight their way through dense packing, performance would collapse at high rates. The fact that it did not confirms that the engineered channels substantially mitigate diffusion resistance throughout the fiber’s cross-section.

What makes this work particularly significant is its generality. The authors frame their methodology as a universal design paradigm for next-generation composite materials that require dynamic ion transport. Dense assemblies of one-dimensional nanomaterials are not limited to carbon nanotubes; nanowires, nanofibers, and other elongated building blocks face the same packing-accessibility dilemma whenever they are assembled into macroscopic forms. A spacing strategy that works during co-assembly, requires no complex active-material hybrids, and preserves the intrinsic structure of the constituent nanomaterials could therefore be applied far beyond the supercapacitor context in which it was demonstrated here. The approach also avoids covalent modification of the nanotubes, which is important because covalent chemistry on carbon surfaces introduces defects that degrade the electrical conductivity that makes nanotubes valuable in the first place.

The research was carried out at the Advanced Conductive Materials Research Center, the Carbon Composite Materials Research Center, and the Functional Composite Materials Research Center of the Korea Institute of Science and Technology in Wanju, Republic of Korea. It was supported by the Nano and Material Technology Development Programs through the National Research Foundation of Korea, funded by the Ministry of Science and ICT, as well as by a KIST Institutional Program. The work was published as an open-access article on 10 September 2026, making the full technical details freely available to researchers worldwide.

For a field that has spent decades chasing ways to make carbon nanotube assemblies live up to their nanoscale promise, the message of this study is refreshingly constructive. Rather than treating dense packing as an unavoidable compromise, the researchers showed that molecular-level design, using nothing more exotic than a soft polymer and the thermodynamics of liquid crystalline assembly, can unlock the hidden interior of a nanotube fiber while keeping its celebrated strength and conductivity intact. If the strategy proves as transferable as the authors suggest, the dense-but-dead interiors of one-dimensional nanomaterial assemblies may soon become some of the most valuable real estate in materials science.

Subject of Research: Liquid crystalline co-assembly of carbon nanotube and poly(vinyl alcohol) hybrid fibers to open interstitial channels for enhanced interfacial ion transport

Article Title: Bottom-up co-assembly of carbon nanotube and soft polymer hybrids: unlocking interstitial channels for enhanced interfacial ion kinetics

Article References: Ryu, K.-H., Lee, S., Lim, S.-I., Kim, S. G., Kim, S. M., Kim, N. D., Hwang, J. Y., Moon, S. Y., Yu, H., Jeong, H. S., & Kim, D.-Y. (2026). Bottom-up co-assembly of carbon nanotube and soft polymer hybrids: unlocking interstitial channels for enhanced interfacial ion kinetics. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02076-z

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02076-z

Keywords: carbon nanotubes, poly(vinyl alcohol), liquid crystals, co-assembly, nanocomposites, composite fibers, interstitial channels, ion diffusion, specific capacitance, supercapacitors, soft matter, Korea Institute of Science and Technology

The scientific foundation of the new device is the thermogalvanic effect, an electrochemical phenomenon in which a temperature gradient applied across a redox-active electrolyte generates a measurable voltage. In a conventional thermogalvanic cell, two electrodes are held at different temperatures while reversible oxidation and reduction reactions proceed at different rates at each electrode. The imbalance in reaction equilibria produces a difference in electrode potential, and the resulting thermovoltage can drive a current through an external circuit. Because the effect does not require boiling fluids, turbines, or mechanical motion, it is particularly attractive for harvesting low-grade heat, the diffuse thermal energy below roughly 100 degrees Celsius that is released by industrial processes, cooling operations, electronics, and even the human body. Converting such small temperature differences into useful electricity has long been difficult, and most existing approaches either deliver too little power or rely on expensive, resource-constrained materials.

That last point is where the new study makes its most distinctive contribution. Many high-performing thermogalvanic systems depend on metal-based redox couples, such as ferroferricyanide complexes, which raise questions about cost, resource availability, and environmental sustainability at scale. The researchers instead turned to lignin, the aromatic biopolymer that gives wood its rigidity and that accumulates in enormous quantities during chemical pulping. Lignin and its sulfonated derivatives are rich in phenolic structures, which include quinone and hydroquinone moieties. These functional groups are electrochemically active and can shuttle reversibly between oxidized and reduced states, making them natural candidates for a redox electrolyte derived entirely from renewable biomass. In effect, the researchers recognized that the very molecules paper mills discard are already equipped with the chemical machinery needed for thermoelectrochemical energy conversion.

To activate this machinery, the team combined lignosulfonate with ammonium persulfate, a strong oxidizing agent. The persulfate oxidizes a portion of the lignin-derived phenolic groups, establishing a redox couple between quinone and hydroquinone species within the solution. When a temperature gradient is applied across this liquid electrolyte, the temperature-dependent equilibria of these reversible reactions generate a thermovoltage between the electrodes. The researchers systematically optimized the composition of the liquid system and reported a Seebeck coefficient of 2.92 millivolts per kelvin, a figure that quantifies how much voltage the electrolyte produces per unit of temperature difference. For a waste-derived material, this performance is notable, and it established a promising baseline before the team moved to the more challenging task of immobilizing the electrolyte in a solid-like form.

Liquid electrolytes, however mobile and conductive, are awkward for practical devices. They can leak, evaporate, and require careful containment, which complicates the design of wearable, flexible, or integrated power units. The researchers therefore embedded their lignosulfonate-based electrolyte into a poly(vinyl alcohol) matrix using freeze-thaw gelation, a simple physical crosslinking process in which repeated freezing and thawing cycles induce the polymer chains to organize into a stable hydrogel network. The resulting quasi-solid material, designated LSAK/PVA, retains the redox-active lignin chemistry while gaining the mechanical robustness and form factor of a gel. This strategy follows a broader trend in energy materials research, in which functional liquids are gelled to combine electrochemical performance with the handling advantages of solids, but it is unusual in sourcing the entire redox system from an industrial waste stream.

The gel did not merely preserve the performance of the liquid; it improved on it. At an optimized lignosulfonate concentration, the LSAK/PVA thermogalvanic gel achieved a Seebeck coefficient of 4.3 millivolts per kelvin, substantially higher than the liquid precursor, along with a maximum output power density of 976 microwatts per square meter per square kelvin. To demonstrate that individual gel elements could be scaled into something practically useful, the researchers connected eleven units in series. Under a temperature difference of 40 kelvin, the series-connected device generated approximately 1.56 volts and delivered 1.75 microwatts of power, enough to operate small electronic devices such as a timer and a calculator. While these power levels are modest in absolute terms, they are meaningful for the growing ecosystem of low-power electronics, sensors, and Internet-of-Things nodes that require only microwatts to function and that could otherwise depend on batteries with limited lifetimes.

Perhaps the most conceptually elegant demonstration in the study involves the waste stream itself. Rather than treating black liquor merely as a source of lignosulfonate feedstock, the researchers showed that the material could directly harvest the heat released as hot black liquor cools. When heated black liquor was allowed to cool, the gel system generated an open-circuit voltage of about 45 millivolts during the cooling process. This result illustrates a circular scenario in which a single industrial by-product serves simultaneously as the active redox material of the energy converter and as the thermal source that drives it. Pulp mills handle black liquor at high temperatures as a matter of routine, and capturing even a portion of the thermal energy released during its processing, using a device built from the liquor’s own constituents, would add a new layer of value to an operation that already recovers significant energy by combustion.

The gel’s abilities extend beyond waste heat into solar energy harvesting, which broadens its potential deployment considerably. Under simulated sunlight with an irradiation intensity of 1 kilowatt per square meter, comparable to standard terrestrial solar conditions, the gel developed an internal temperature difference of approximately 25 kelvin and generated an open-circuit voltage of about 0.1 volt. The photothermal conversion relies on the gel’s ability to absorb sunlight and establish a thermal gradient across its thickness, which the thermogalvanic chemistry then translates into electricity. Stability is a critical concern for any device intended for continuous outdoor operation, and the researchers addressed this with a five-cycle test that showed stable voltage output across repeated illumination cycles. Encouragingly, the performance carried over from the laboratory to the field: an outdoor device exposed to natural sunlight produced a thermovoltage of 0.33 volts after 30 minutes of light exposure, indicating that the material can function under real, variable environmental conditions rather than only under carefully controlled lamps.

Taken together, the results sketch a material strategy with implications that reach well beyond the paper industry. The authors suggest that lignin-based thermogalvanic materials could provide a pathway for recovering otherwise underused low-grade thermal energy while simultaneously adding value to industrial biomass waste. In this framing, lignin is no longer merely a low-cost fuel or a feedstock for commodity chemicals but an active functional component in energy conversion devices. The approach aligns with the principles of waste valorization, in which residues are upgraded into products of higher economic and functional value, and it does so using abundant, metal-free chemistry that avoids the supply-chain and environmental concerns associated with many inorganic thermoelectric materials. If the performance of such gels can be further improved and their manufacture integrated into existing pulp mill operations, the dark by-product of papermaking could find a second life as a soft, sustainable material that quietly harvests the heat and sunlight that would otherwise simply dissipate.

Subject of Research: Lignin-based thermogalvanic gels from papermaking waste for heat and solar energy conversion

Article Title: Papermaking waste turned into a gel for harvesting heat and sunlight

Article References: Papermaking waste turned into a gel for harvesting heat and sunlight. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: thermogalvanic gel, lignin, lignosulfonate, black liquor, waste heat recovery, solar energy, thermogalvanic effect, biomass valorization, poly(vinyl alcohol), Seebeck coefficient, papermaking waste, redox electrolyte