polyethylene glycol – Science

PEG Polymer Doubles as Dispersant, Template and Porogen in High-Entropy Oxide Supercapacitor Electrode

Neil Sanderson — Sat, 17 Oct 2026 14:28:28 +0000

High-entropy oxides (HEOs) have attracted considerable attention for energy storage applications because of their multi-principal synergistic effects and excellent structural stability. In this study, polyethylene glycol (PEG) was used as a surfactant to synthesize (CrMnFeCoNi)3O4 HEOs by tuning the molar ratio of PEG to metal cations (P/M). The results show that PEG plays three roles during synthesis, serving simultaneously as a coordinating dispersant, a structure-directing agent, and an in situ porogen. The optimized HEO (P/M = 4/5) exhibits a uniform nanoparticle morphology and a well-developed pore architecture, delivering a specific capacitance of 557.6 F g−1. Kinetic analysis further indicates that its pseudocapacitive behavior arises from a cooperative effect involving both capacitive-controlled and diffusion-dominated mechanisms. The assembled asymmetric supercapacitor device achieves an energy density of 64.2 Wh kg−1 at a power density of 375.3 W kg−1 and retains 81.3% of its capacitance after 10,000 charge/discharge cycles. These outstanding electrochemical properties highlight the promise of PEG-templated (CrMnFeCoNi)3O4 HEOs for advanced energy storage applications.

Subject of Research: PEG polymer shapes a five-metal high-entropy oxide into a porous supercapacitor electrode delivering 557.6 F g−1 and 64.2 Wh kg−1.

Article Title: PEG-mediated particle assembly and pore evolution in a Cr–Mn–Fe–Co–Ni spinel high-entropy oxide

Article References: Zeng, F., Xu, B., Jing, C., He, X., Li, C., & Li, G. (2026). PEG-mediated particle assembly and pore evolution in a Cr–Mn–Fe–Co–Ni spinel high-entropy oxide. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13928-w

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13928-w

Keywords: high-entropy oxide, supercapacitor, polyethylene glycol, energy storage, spinel oxide, pseudocapacitance, PEG-mediated, particle, assembly, pore, evolution, spinel

Common Polymer additive Boosts Quantum-Dot LED Efficiency with a Simple Surface Treatment

Katie Riggs — Sat, 17 Oct 2026 11:28:51 +0000

A dash of an everyday polymer may be all it takes to squeeze more light out of quantum-dot light-emitting diodes. In a study published in the Journal of Materials Science, a team of researchers from Phenikaa University, VNU University of Engineering and Technology, and the Vietnam Academy of Science and Technology reports that treating the emissive region of CdSe/ZnS quantum-dot LEDs with polyethylene glycol, better known as PEG, substantially improves how efficiently injected electrical current is converted into visible light. The work, led by Huu Tuan Nguyen of Phenikaa University, offers a low-cost, solution-based route to better quantum-dot displays without redesigning the entire device stack.

Quantum-dot LEDs, or QLEDs, are among the most promising technologies for next-generation displays because the nanoscale semiconductor crystals at their heart emit extremely pure, tunable colors. In the devices studied here, the light-emitting layer consists of cadmium selenide cores wrapped in zinc sulfide shells, sandwiched between charge-transport layers that steer electrons and holes toward the dots. When the two types of charge meet inside a quantum dot, they can recombine radiatively and emit a photon, or they can be lost through non-radiative pathways and defects. The fraction of current that ends up as light, rather than heat or leakage, is what determines a display’s brightness and energy efficiency, and it is precisely the quantity the Vietnamese team set out to improve.

The researchers’ strategy targeted the interface between the hole-transport polymer poly-TPD and the quantum-dot layer, a region widely recognized as a bottleneck in these devices. By applying a PEG-assisted modification to this poly-TPD/QD region, they altered the physical and electrical character of the junction where holes are injected into the emissive layer. Compared with an otherwise identical untreated device, the PEG-treated QLED showed a lower current density at a given voltage together with higher luminance, higher current efficiency, and higher external quantum efficiency. Taken together, those trends point to a cleaner conversion of injected current into photons: less current flows, but more of what does flow produces light.

The headline numbers are striking for such a simple intervention. The maximum luminance of the treated devices increased by approximately 1.8-fold, while the maximum current efficiency rose by approximately 1.6-fold. In practical terms, the modified LEDs could be driven roughly twice as bright, and every milliamp of current delivered roughly sixty percent more light. For display manufacturers, improvements of this magnitude achieved through a solution-processable additive, rather than new materials or vacuum deposition steps, are exactly the kind of incremental engineering that compounds into commercially meaningful gains.

To understand where the improvement came from, the team examined the surface quality of the deposited quantum-dot films using atomic force microscopy. The measurements revealed a decrease in the root-mean-square roughness of the film from 1.367 nanometers to 0.829 nanometers after PEG treatment, even though the overall topographical features remained qualitatively similar. That smoothing matters because rough, uneven films create local thickness variations and poorly contacted regions where charge can accumulate, leak, or recombine without emitting. A flatter emissive layer promotes more uniform current spreading and more consistent contact between the quantum dots and the adjacent transport layers, which is consistent with the improved current-to-light conversion the team observed.

The electrical analysis went beyond simple current-voltage curves. The researchers fitted the forward-bias current density-voltage characteristics using a modified Shockley-type expression, a phenomenological device-level model borrowed from classical diode physics and adapted for the layered reality of QLEDs. Two extracted parameters proved especially informative: the effective ideality factor, which describes how far the device departs from ideal diode behavior, and the current prefactor, which sets the overall scale of the current response. PEG treatment produced lower values of both parameters, alongside a higher effective series resistance.

The authors are notably careful about what these fitted parameters do and do not mean. They emphasize that the ideality factor and prefactor describe the aggregate non-ideal electrical response of the entire multilayer device and should not be interpreted as direct measurements of leakage current, trap density, or non-radiative recombination. That restraint is a welcome corrective to a common pitfall in the LED literature, where ideality factors are often over-interpreted as clean probes of specific loss mechanisms. In a device with many stacked layers and interfaces, a single diode equation can only summarize the combined behavior, and the Vietnamese team frames their findings accordingly, discussing the performance enhancement as a correlation among PEG treatment, surface topography, and device-level charge transport rather than claiming a single microscopic cause.

The higher effective series resistance in the treated devices fits naturally with the observed lower current density. PEG, an insulating polymer, appears to moderate the flow of charge through the modified region, suppressing parasitic current paths that consume current without generating light. The trade-off is favorable: the modest additional resistance costs some current, but the current that remains is used far more productively in the emissive dots. This echoes a recurring theme in quantum-dot optoelectronics, where the goal is not to maximize current but to balance electron and hole injection so that charges meet and recombine where they should.

PEG itself is an intriguing choice of additive. The inexpensive, water-soluble polymer has a track record in organic and hybrid electronics, where it has been used to modify the conductivity of PEDOT:PSS electrodes and to passivate zinc oxide electron-transport layers in blue quantum-dot LEDs. Its ether-linked oxygen atoms can coordinate to surface sites and its polymer chains can mediate film morphology, making it a versatile interfacial agent. The new study extends this toolkit to the poly-TPD/quantum-dot interface in CdSe/ZnS devices, showing that the same benign chemistry can smooth films and reshape charge transport in a full LED stack.

The work was supported by the National Foundation for Science and Technology Development of Vietnam under Project 103.03-2023.80, and the authors state that the data supporting the findings are available within the article. While Cd-based quantum dots face regulatory scrutiny in consumer products, the interfacial modification strategy demonstrated here is material-agnostic in principle and could transfer to cadmium-free emitters such as the InP-based dots now driving commercial development. For a field chasing every last percent of efficiency, the message of this study is refreshingly simple: sometimes the biggest gains come not from new nanocrystals, but from treating the surfaces you already have with a polymer you can buy by the bottle.

Subject of Research: PEG-assisted interfacial modification for improved efficiency of CdSe/ZnS quantum-dot light-emitting diodes

Article Title: Improved current-to-light conversion in CdSe/ZnS quantum-dot light-emitting diodes through PEG-assisted interfacial modification

Article References: Nguyen, H. T., Duong, A. T., Van Hoang, N., Nguyen, D. L., & Nguyen, T. H. (2026). Improved current-to-light conversion in CdSe/ZnS quantum-dot light-emitting diodes through PEG-assisted interfacial modification. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13950-y

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13950-y

Keywords: quantum dots, QLED, CdSe/ZnS, polyethylene glycol, PEG, poly-TPD, external quantum efficiency, atomic force microscopy, ideality factor, charge transport, interfacial modification, display technology

Why Big PEGs Never Cross the Gut Wall: New Review Maps the Science and Safety of Osmotic Laxatives

Louis Brooks — Thu, 15 Oct 2026 18:46:03 +0000

A detailed review published in Frontiers in Drug Safety and Regulation has brought renewed attention to one of the most quietly consequential questions in medicine: what actually happens when we swallow large molecules? The work, led by Chiara G. M. Gennari and colleagues at the Department of Pharmaceutical Sciences of the University of Milan, examines polyethylene glycols, or PEGs, as a reference system for understanding the physiological limits of intestinal absorption. Their conclusions carry implications not only for the millions of people who take PEG-based laxatives every year, but also for regulators who must decide how substances that act physically rather than pharmacologically should be classified and controlled.

The intestine performs one of biology’s most remarkable balancing acts. It must allow the selective passage of nutrients while blocking potentially harmful substances, a feat achieved through a multilayered barrier composed of specialized epithelial cells called enterocytes, tight junctions that govern the spaces between cells, a thick mucus layer, and an intricate mucosal immune system. Under normal conditions, most macromolecules, including proteins, peptides, and synthetic polymers, are either degraded before they can be absorbed or excluded from passage altogether. Their sheer size prevents them from squeezing through the tight junctions of the paracellular pathway, and their hydrophilic, water-loving nature makes it difficult for them to dissolve into and cross lipid cell membranes via the transcellular route. Only in special circumstances, such as in newborns or in states of inflammation and mucosal damage, can endocytosis or increased paracellular permeability permit larger compounds to slip through.

PEGs, also known as macrogols, are a family of synthetic polyether polymers produced by polymerizing ethylene oxide with water or ethylene glycol. Their behavior in the gut depends almost entirely on molecular weight, which makes them uniquely useful probes of the intestinal barrier. Low molecular weight PEGs of 200 to 600 grams per mole are clear, viscous liquids that can be absorbed through the gastrointestinal mucosa and excreted unchanged in urine, which is precisely why PEG 400 has long been used in permeability tests to detect barrier alterations in conditions such as celiac disease and chronic inflammatory bowel disease. High molecular weight PEGs, by contrast, such as PEG 3350 and PEG 4000, are waxy solids or powders that pass through the digestive tract essentially untouched, acting as osmotic laxatives by coordinating water molecules in the intestinal lumen.

The pharmacokinetic evidence assembled in the review reveals a striking molecular-weight gradient. Urinary recovery studies, a proxy for systemic absorption, show that low molecular weight PEGs can reach up to 60 percent of an administered dose in healthy humans, and roughly 20 to 36 percent in animals, a phenomenon correlated with solvent drag through aquaporins, the ubiquitous membrane channels that transport water and some solutes during osmotic processes. For PEG 2000, absorption falls below 4 percent. For PEG 3350, reported absorption ranges from 0.01 to 0.28 percent, and for PEGs above 4000 grams per mole it drops below 0.08 percent. Human intestinal perfusion studies using solutions containing 1 gram per liter of PEG 3350 recovered 99 percent and 109 percent of the polymer in the effluent, confirming that it is essentially not absorbed. This pattern is so well established that the ICH M9 guideline on biopharmaceutics-based biowaivers lists PEG 4000 as a zero-permeability model drug for validating Caco-2 cell permeability assays.

The mechanism behind this exclusion is partly thermodynamic. Each ethylene glycol repeat unit binds approximately three water molecules, a strong interaction that dramatically increases the effective steric bulk of the polymer and blocks its paracellular transport through the epithelium. The tight junction architecture imposes a stringent steric limit, typically below 1 nanometer, that excludes polymers the size of PEG 3350 and 4000 even when junctional regulation is disrupted. The review also addresses a clinically important question: what happens in diseased guts? Conditions with mucus depletion, such as active ulcerative colitis, Crohn’s disease, or severe infectious enteritis, may weaken the mucus filter, and mucositis or celiac inflammation can transiently loosen paracellular barriers. Yet even in these settings, evidence indicates that PEGs above 3 to 4 kilodaltons still experience substantial size-dependent exclusion, and no clinical or experimental data support meaningful absorption of high molecular weight PEGs even in critical illness or short-bowel syndrome.

But the review does not stop at a clean verdict. The authors raise a subtle analytical problem that could reinterpret some of the literature: PEGs produced by polymerization are inherently polydisperse, meaning any batch of PEG 3350 or 4000 contains a small residual fraction of low molecular weight chains. The United States Pharmacopeia accepts an impurity level of up to 3 percent for pharmaceutical-grade PEG 3350, with an apparent weight-average molecular weight between 3015 and 3685 grams per mole. This means that the tiny absorbed fractions reported in some studies, the reviewers argue, might actually reflect uptake of low molecular weight impurities rather than the bulk polymer. Supporting this hypothesis, experiments by Winne and Gorig with radiolabeled PEG 4000 in rats showed that the apparent absorbed material consisted mainly of lower molecular weight impurities present in the commercial batches.

The analytical challenge is far from trivial. PEG lacks chromophores, making direct UV-visible detection difficult, and its extreme hydrophilicity causes poor retention on standard C18 HPLC columns. Mass spectrometry struggles with the formation of multiple charge states from protons and metal ions, producing overlapping oligomeric distributions. Liquid chromatography-tandem mass spectrometry remains the gold standard for quantifying PEG in biological matrices at nanogram-per-milliliter sensitivity, while size exclusion chromatography coupled with multi-angle light scattering is preferred for determining absolute molecular weight distributions in quality control, though it is less sensitive. High-resolution mass spectrometry excels at resolving individual oligomers and impurities but demands intensive computation. Pelham and colleagues reported a relative error of 15 percent for serum PEG quantification methods, underscoring how much uncertainty may have crept into older pharmacokinetic measurements that could not distinguish PEG fractions of different chain lengths.

On the therapeutic side, the case for high molecular weight PEGs is strong. By retaining large amounts of water in the intestinal lumen, they soften stool and ease defecation, while the resulting increase in endoluminal pressure indirectly stimulates peristalsis. They are the first recommended treatment for constipation in children, outperforming lactulose, stimulant laxatives such as senna and picosulfate, milk of magnesia, and probiotics in comparative studies. A 2003 safety study tracking 83 children over three months found PEG 3350 therapy clinically and biochemically safe, with similar results reported in infants. Excipients such as sodium, potassium, and bicarbonate maintain isotonicity so that fluid exchange between body and gut remains neutral, and clinical evidence confirms they neither damage the mucosa nor enhance permeability; PEG is recovered unchanged in feces regardless of formulation, with any salts merely accelerating transit by increasing the osmotic load.

The regulatory conclusion follows directly from the pharmacology. Because PEG 3350 and 4000 are neither absorbed nor metabolized in the gastrointestinal tract, they qualify under Rule 21 of Annex VIII of Regulation (EU) 2017/745 as Class IIb substance-based medical devices intended for short-term use of up to thirty days, based on their purely physical, local mechanism of action in the gut. The same non-permeability that makes them safe for daily use also makes them indispensable diagnostic markers of intestinal integrity, in which role they are marketed as medicinal products. The Milan team’s synthesis ultimately reframes a familiar pharmacy-shelf product as a window onto the fundamental architecture of the human intestinal barrier, and as a reminder that in physiology, size really is destiny.

Subject of Research: Gastrointestinal absorption and regulatory classification of high molecular weight polyethylene glycols

Article Title: Oral absorption of high molecular weight polyethylene glycols: mechanistic, safety and regulatory insights

Article References: Gennari, C. G. M., Azari, S., Casiraghi, A., & Musazzi, U. M. (2026). Oral absorption of high molecular weight polyethylene glycols: mechanistic, safety and regulatory insights. Frontiers in Drug Safety and Regulation, 6, Article 1851318. https://doi.org/10.3389/fdsfr.2026.1851318

Image Credits: AI Generated

DOI: 10.3389/fdsfr.2026.1851318

Keywords: polyethylene glycol, PEG 3350, intestinal barrier, osmotic laxatives, macromolecule absorption, tight junctions, medical devices, Regulation EU 2017/745, pharmacokinetics, intestinal permeability, USP impurities, constipation

Thermal Welding of Biodegradable Polymer and Graphene Oxide Yields Leak-Proof Heat Storage Materials

Neil Sanderson — Fri, 09 Oct 2026 04:09:17 +0000

Phase-change materials have long promised a way to bottle heat: absorb it when the sun shines or when industrial waste streams run hot, and release it slowly when temperatures drop. The problem has always been containment. Most high-performing phase-change materials melt into a liquid at exactly the moment they are doing their job, so without a rigid, leak-proof scaffold they ooze, seep and eventually fail. A study published in the Journal of Materials Science by Yunbin Zhang, Dajun Luo, Xueliang Zhang and Yong Deng, researchers at Guizhou University and the Guizhou Institute of Technology, now reports a remarkably simple answer built from two unlikely partners: a fully biodegradable plastic and graphene oxide, welded together by nothing more exotic than heat.

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

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

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

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

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

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

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

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

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

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

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

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

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13861-y

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

A Bacterial Toxin’s Random Flickers Reveal Hidden Complexity in Nanopore Sensing

Bethany Barker — Fri, 09 Oct 2026 03:01:05 +0000

Deep inside one of biology’s most famous molecular machines, a team of Brazilian researchers has found something surprising: a stream of electrical signals that behaves less like a predictable circuit and more like pure chance. In a study published in Discover Chemistry, scientists led by Gesilda F. Neves and Romildo A. Nogueira applied a mathematical tool borrowed from information theory, known as Lempel-Ziv complexity, to the flickering ionic currents that pass through a single alpha-hemolysin nanopore. Their results offer a fresh quantitative window into the stochastic nature of single-molecule sensing, a phenomenon that underpins technologies from DNA sequencing to the detection of trace chemicals in complex samples.

Alpha-hemolysin is an exotoxin secreted by the bacterium Staphylococcus aureus. In its active form, the protein is built from 293 water-soluble amino acids that assemble into a heptameric pore, a seven-part barrel that punches through cell membranes. That structure, first resolved in crystallographic detail in the 1990s, has made alpha-hemolysin the workhorse of stochastic sensing: the first and still most widely used biological nanopore for detecting individual molecules. When a single pore is embedded in an artificial membrane bathed in electrolyte and a voltage is applied, a steady ionic current flows through the opening. When an analyte molecule wanders into the pore, it partially obstructs that current, producing a characteristic downward blip. Each blip corresponds to one molecule, and the pattern of blips over time carries information about the analyte’s identity and concentration.

In the new experiments, the team used monodisperse polyethylene glycol of molecular weight 1294, abbreviated PEG 1294, as the analyte. The experimental platform was a solvent-free planar lipid bilayer assembled by the classic Montal and Mueller technique: two monomolecular lipid films were apposed across a hole roughly 100 micrometers in diameter in a Teflon partition, forming a barrier that separated two identical compartments of a Teflon chamber. The synthetic lipid 1,2-diphytanoyl-sn-glycero-3-phosphocholine was used at 2 percent by weight in hexane, and the hole was pretreated with a dilute hexadecane solution to promote stable bilayer formation. Both compartments held a concentrated electrolyte of 4 molar potassium chloride buffered with 5 millimolar Tris-citric acid at pH 7.5. Alpha-hemolysin was added to one side, the cis side, at a concentration tuned so that exactly one pore inserted into the membrane.

The researchers then added PEG 1294 to the opposite, trans side at two concentrations, 400 and 1000 micromolar, and applied voltages ranging from +20 to +100 millivolts in 20 millivolt steps. Ionic currents were recorded with an Axopatch 200B amplifier in voltage clamp mode, using silver/silver chloride electrodes connected through agar salt bridges. The signals were low-pass filtered at 15 kilohertz and digitized at a sampling rate of 250 kilohertz, all at a controlled temperature of 25 degrees Celsius. Under these conditions, the current trace showed the textbook signature of stochastic sensing: stepwise transitions between a fully open level and a partially blocked level, each step corresponding to the entry or exit of a single PEG molecule from the pore lumen.

The novelty of the study lay not in the electrophysiology but in the analysis. Rather than focusing on conventional metrics such as event duration or blocking depth, the team turned to Lempel-Ziv complexity, a measure introduced in 1976 by Abraham Lempel and Jacob Ziv to quantify the randomness of finite sequences. The method works by converting a time series into a binary string: each data point is compared with the average of the entire series, receiving a 1 if it exceeds the average and a 0 if it falls below. The resulting string of ones and zeros is then scanned from left to right, and a counter increments every time a new, previously unseen substring appears. Finally, the counter is normalized by a theoretical upper bound, n divided by the base-2 logarithm of n, yielding a complexity value that ranges from 0 to 1 and is independent of sequence length.

The interpretation of this number is intuitive. A value close to 1 indicates a highly random, unpredictable signal with little internal self-similarity, while a value close to 0 indicates a repetitive, ordered series. Lempel-Ziv complexity has previously found applications in biomedical signal analysis, including studies of electroencephalogram background activity in Alzheimer’s disease patients and the detection of ventricular tachycardia and fibrillation in cardiac recordings. Applying it to nanopore data, however, allowed the researchers to ask a question that conventional event statistics cannot easily answer: how complex, in an information-theoretic sense, is the pattern of molecular blocking events?

The answer depended strongly on how much analyte was present. At the lower PEG concentration of 400 micromolar, complexity values were consistently lower than at 1000 micromolar, across every voltage tested. The full range of measured values stretched from a minimum of 0.45, recorded at 400 micromolar and +40 millivolts, to a maximum of 0.97, recorded at 1000 micromolar and +80 millivolts. The physical explanation is straightforward: higher analyte concentrations produce more frequent blocking events, filling the time series with rapid alternations between open and blocked states and pushing the complexity measure toward its upper limit. At lower concentrations, longer stretches of open-pore current dominate, and the signal becomes more ordered and less random.

To probe whether the apparent order at low concentration reflected genuine structure or simply sparse sampling, the researchers performed a clever control. They segmented the original time series recorded at 400 micromolar, shuffled the segments into a random order, and recalculated the complexity of the resulting randomized series. For every applied potential, the shuffled data yielded higher Lempel-Ziv values than the original recordings. This result is diagnostic: if the original series had already been maximally random, shuffling it would have changed nothing. The fact that randomization increased complexity means the unshuffled sequences contained residual structure, and that the biosensor’s output at low analyte concentration falls short of full stochastic behavior.

The team also compared series built exclusively from blocked periods with series built exclusively from unblocked periods, at both concentrations and all voltages. Statistical analysis using Student’s t-test, with a significance threshold of p less than 0.05, found no meaningful differences between the complexity of the blocked-only and unblocked-only series, nor between those segmented series and the original combined recordings. In other words, the complexity of the signal does not reside preferentially in either the moments when PEG occupies the pore or the intervals between occupations; the stochastic character is distributed across the entire record.

The broader implications reach into a long-standing debate in biology about the role of randomness. Molecular biology has traditionally leaned on deterministic principles, yet stochasticity is now recognized as a genuine feature of living systems rather than mere noise. Ion channel kinetics are widely treated as stochastic events, and some theorists argue that intrinsic randomness in the nervous system may even enable flexible decision-making. As the authors note, biological studies often lack the tools to distinguish chaotic, noisy, deterministic, and probabilistic behavior. Lempel-Ziv complexity offers one such tool. Their conclusion is nuanced: the alpha-hemolysin biosensor behaves in a purely stochastic fashion only at higher analyte concentrations, while at lower concentrations its stochasticity diminishes, though it can be mathematically restored by randomizing the event sequence. For engineers designing nanopore sensors, that finding matters, because the reliability of single-molecule detection depends on understanding when the digital current signature is truly random and when it carries hidden structure that smarter algorithms might exploit.

Subject of Research: Stochastic analysis of alpha-hemolysin nanopore ionic current blocking events using Lempel-Ziv complexity

Article Title: Analyzing alpha-hemolysin nanopore behavior using Lempel-Ziv complexity

Article References: Neves, G. F., Machado, D. C., Consoni, L. H. A., Costa, E. V. L., Carneiro, C. M. M., Rodrigues, C. G., & Nogueira, R. A. (2026). Analyzing alpha-hemolysin nanopore behavior using Lempel-Ziv complexity. Discover Chemistry, 3(1), Article 571. https://doi.org/10.1007/s44371-026-01022-8

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01022-8

Keywords: alpha-hemolysin, nanopore, Lempel-Ziv complexity, stochastic sensing, polyethylene glycol, ion channel, planar lipid bilayer, biosensor, information theory, single-molecule detection, biophysics, stochasticity

Mangrove-Inspired Membrane Pulls Drinking Water From Air at Record Speed

Denise Maddox — Thu, 08 Oct 2026 21:18:11 +0000

Freshwater scarcity is one of the defining challenges of a warming, crowded century, and one of the most tantalizing answers has been hanging in the air all along. The atmosphere holds vast quantities of water vapor, even in arid regions, and devices that can capture and release that moisture on demand promise decentralized drinking water without desalination plants, pipelines, or aquifers. Now, a team of researchers reporting in Advanced Science has unveiled a biomimetic membrane that borrows a trick from mangrove trees and, in doing so, appears to dissolve one of the most stubborn trade-offs in the field: the choice between how much water a material can hold and how fast it can grab it.

The technology belongs to a family known as sorption-based atmospheric water harvesting, or SAWH. Unlike condensation systems, which chill air below its dew point and demand substantial electrical power, sorption-based systems use hygroscopic materials that soak up vapor at ambient temperature and then release it when gently heated, often by nothing more than sunlight. That makes them attractive for off-grid communities, remote islands, and agricultural settings. But the leading materials, salt-composite hydrogels, have long suffered from a kinetic bottleneck. Loading more hygroscopic salt raises the total water capacity, yet it also thickens the internal diffusion barrier, so the material takes longer to reach its capacity. A sorbent that needs hours to saturate simply cannot cycle often enough to be productive.

The new work traces that bottleneck to a transport problem with two coupled stages. Water vapor must first find and bind to hygroscopic sites, and the resulting salt solution must then redistribute through the polymer network. Previous analyses have suggested that, under representative conditions, liquid diffusion inside the hydrogel is often the dominant resistance, not the arrival of vapor from the surrounding air. Earlier attempts to speed things up focused on porous architecture: ice-templating, foaming, and directional freeze-drying all shorten diffusion distances. But those approaches are energy-intensive, add processing complexity, and never fully solve the deeper issue that much of the salt remains buried inside the polymer matrix, out of direct contact with the air it is supposed to be drinking from.

The inspiration for a different solution came from the grey mangrove, Avicennia marina, a plant that thrives while rooted in seawater. The mangrove transports salt ions from its internal tissues to specialized glands on its leaf surface, where the salt accumulates in microstructured regions. Under humid conditions, that surface salt deliquesces and pulls moisture straight out of the atmosphere. The research team realized that the most valuable feature was not the plant’s physiology but its geometry: a spatial separation between internal salt transport and storage on one hand, and surface-exposed, air-accessible hygroscopic sites on the other. A synthetic material built on that principle could let vapor meet salt immediately, without waiting for moisture to fight its way through a dense gel.

Translating that idea into hardware, the researchers fabricated what they call a multi-layer heterogeneous hygroscopic membrane, or MHH membrane. It is a sandwich structure made by alternating electrospinning and spraying. First, a porous mat of polyacrylonitrile nanofibers is electrospun onto a collector. Then, pre-formed brush-like hydrogel microspheres, roughly 100 micrometers across, are sprayed onto the fiber scaffold. A second round of electrospinning encapsulates the hydrogel, producing a nanofiber-hydrogel-nanofiber stack. The outer nanofiber layer is coated with polypyrrole, a black polymer that absorbs sunlight efficiently, and the whole membrane is loaded with lithium chloride, one of the most powerful hygroscopic salts known. The final membrane carries about 170 grams of salt per square meter.

The clever part is what happens during drying. When the saturated membrane is regenerated, salt solution is driven out of the hydrogel and crystallizes in the voids of the outer nanofiber layer, right at the air interface. On the next adsorption cycle, that surface-enriched salt meets humid air directly and deliquesces almost immediately, and the resulting solution is then drawn into the hydrogel reservoir below. Energy-dispersive X-ray spectroscopy confirmed the effect: the membrane surface showed a chlorine-to-carbon atomic ratio of 10.80, compared with just 1.27 on the surface of conventional hydrogel microspheres loaded with the same amount of salt. Cross-sectional imaging found substantial salt deposits occupying the inter-fiber voids of the outer layer, consistent with the redistribution mechanism.

The kinetic payoff is striking. At 25 degrees Celsius and 70 percent relative humidity, both the MHH membrane and the hydrogel microsphere control reach a similar equilibrium uptake of about 2.4 grams of water per gram of material, proving that the layered design sacrifices no storage capacity. But the membrane absorbs roughly 1.4 grams per gram within the first 30 minutes, nearly double the control, and hits 85 percent of equilibrium within 90 minutes. The microspheres need about 300 minutes to reach the same fraction. Fitting the curves with a unified adsorption model yields a characteristic time constant of 40.12 minutes for the membrane versus 110.72 minutes for the microspheres, and an initial sorption rate about 2.1 times higher. Independent measurements of the elementary steps showed why: the hydrogel takes up saline solution faster than the nanofiber layer can generate it by vapor-driven deliquescence, so the interface never floods and vapor capture can continue.

That rapid liquid uptake is itself engineered at the molecular scale. The hydrogel microspheres are not ordinary polyacrylamide; they contain polyethylene glycol side chains grafted onto the network, forming a brush-like architecture. Flexible PEG segments increase chain mobility and accessible free volume, easing the passage of water molecules. In cross-flow vapor permeation experiments, a PAM-co-PEGMA film 0.46 millimeters thick showed a permeation lag time of only about 2 minutes, whereas a plain polyacrylamide film of just 0.14 millimeters lagged roughly 13 minutes. Normalized to a common thickness, the time-lag-derived effective diffusion coefficient of the brush-like hydrogel came out approximately 70 times that of conventional PAM. Swelling tests reinforced the picture: in 10 percent lithium chloride solution, the brush-like hydrogel swelled to about 1000 percent after 240 minutes, versus roughly 600 percent for PAM, with kinetics consistent with Fickian transport rather than sluggish polymer relaxation.

The membrane also regenerates efficiently under sunlight. Coated with polypyrrole on its outer surface, it releases about 70 percent of its stored water within 90 minutes under one-sun illumination, compared with about 60 percent for the microspheres, and its surface temperature exceeds 70 degrees Celsius within 20 minutes, roughly 10 degrees hotter than the control. Because the photothermal layer sits at the evaporation interface rather than dispersed through a hydrated gel, heat is generated exactly where water leaves. Durability held up too: after 20 adsorption-desorption cycles, the membrane retained about 2.5 grams per gram of uptake with overlapping kinetic curves, and salt remained visible in the nanofiber interstices. One honest caveat emerged from a 48-hour exposure to 100 percent humidity, which caused slight saline leakage; the design does not fully confine salt solution under prolonged saturation, though performance recovered after drying.

Crucially, the material-level speed translated into device-level output. The team built a semi-continuous, three-bed harvester in which one bed desorbs under a solar lamp while the others adsorb, cycling every 2 hours of capture and 1 hour of release. In the laboratory at 25 degrees Celsius and 90 percent relative humidity, the device produced 3.47 liters per square meter over 8 hours, an average of 0.43 liters per square meter per hour. Outdoors in Xiamen, under 60 to 65 percent humidity and peak solar irradiance near 830 watts per square meter, the same prototype yielded about 1.62 liters per square meter in a day, and a second field test under cloudier, hotter conditions reached about 1.96 liters per square meter per day. Condensate analysis by ICP-OES found low inorganic contamination, though the authors caution that microbiological safety requires separate system-level measures. The broader lesson may outlast the specific membrane: by engineering interfacial accessibility and internal transport together, across scales from nanofibers to polymer side chains, sorbent designers can finally stop choosing between capacity and speed.

Subject of Research: Biomimetic multi-layer hygroscopic membranes for rapid sorption-based atmospheric water harvesting

Article Title: Interfacial Salt Redistribution Enables Rapid Atmospheric Water Harvesting in a Biomimetic Multi‐Layer Hygroscopic Membrane

Article References: Zhong, F.-Y., Guo, C.-Y., Shao, Z.-D., Zhong, L.-B., Chen, G. Z., Zheng, Y., Zhou, J. L., Zheng, Y.-M., & He, J. (2026). Interfacial Salt Redistribution Enables Rapid Atmospheric Water Harvesting in a Biomimetic Multi‐Layer Hygroscopic Membrane. Advanced Science, Article e78196. https://doi.org/10.1002/advs.78196

Image Credits: AI Generated

DOI: 10.1002/advs.78196

Keywords: atmospheric water harvesting, hygroscopic membrane, mangrove biomimicry, lithium chloride, hydrogel, electrospinning, solar desorption, water scarcity, sorption kinetics, polyethylene glycol, nanofibers, photothermal materials

Gamma Rays and Fake Drought: Mutant Legumes Face a Hydroponic Stress Test

Alan Morgan — Sun, 04 Oct 2026 23:04:14 +0000

In the arid and semi-arid tropics, few forage legumes are as valuable to smallholder farmers as Leucaena tarramba, a fast-growing shrub prized as livestock feed. Yet like so many tropical crops, its productivity hinges on water, and as droughts grow longer and less predictable, breeders are racing to find plants that can keep growing when the rain stops. A new study published in BMC Plant Biology offers a detailed look at how Indonesian researchers are using gamma radiation to create genetic diversity in this legume and then sorting through the resulting mutants with a deceptively simple tool: a hydroponic tank spiked with a chemical that mimics drought.

The research, led by Purnama Isti Khaerani of the Research Center for Genetic Engineering at Indonesia’s National Research and Innovation Agency (BRIN) together with colleagues at Hasanuddin University and partner institutions, tackles a persistent bottleneck in mutation breeding. Irradiating seeds with cobalt-60 gamma rays at doses ranging from 50 to 1000 gray generates thousands of candidate plants, but only a fraction carry useful traits. The team first established the median lethal dose, the radiation level that kills half the seedlings, at 820 gray based on survival 21 days after planting. From the first generation of irradiated plants, they advanced material derived from 0, 250, 500, and 750 gray into the second generation, the M2, where recessive mutations typically begin to reveal themselves.

Screening for drought tolerance in soil is notoriously messy. Water moves unevenly through soil profiles, evaporation varies from pot to pot, and root architecture interacts with substrate in ways that swamp the signal breeders are trying to detect. The Indonesian team sidestepped this problem by growing the M2 seedlings in a deep-water culture hydroponic system and adding polyethylene glycol 6000 to the nutrient solution at concentrations of 10 and 20 percent. PEG is a large, inert polymer that plants cannot absorb; instead, it lowers the water potential of the solution, forcing roots to work harder to take up water. In effect, it reproduces the osmotic component of soil drought with a precision that field trials cannot match, and it does so reproducibly across hundreds of seedlings at once.

The experimental design was a split-plot arrangement, with PEG concentration as the main plot and irradiation dose as the subplot, allowing the researchers to disentangle the effects of stress severity from those of the mutagenic treatment. Seedlings were exposed to the osmotic stress for 42 days after planting in the hydroponic system, and then transferred to a greenhouse for post-hydroponic evaluations at 60 and 90 days after planting. This two-phase approach matters because a plant that survives an artificial osmotic challenge in a tank is not necessarily one that will thrive in a paddock; the later greenhouse measurements served as an early check on whether hydroponic performance carries over into more realistic growing conditions.

The results showed a clear interaction between stress level and radiation dose across several morpho-physiological traits. Under moderate stress of 10 percent PEG, mutants derived from 250 and 500 gray maintained several growth-related traits better than the wild type and showed adaptive physiological responses. At 20 percent PEG, the picture darkened for all entries: growth and physiological performance declined more sharply, reflecting the severity of the osmotic challenge. The researchers quantified that severity using a stress intensity metric, which rose from 0.68 under 10 percent PEG to 0.85 under 20 percent PEG, confirming that the higher concentration imposed a substantially harsher selection environment.

To rank the mutants objectively, the team applied two classic selection indices. The stress tolerance index, or STI, rewards genotypes that yield well both under stress and without it, while the stress susceptibility index, or SSI, penalizes those that lose the most performance when water becomes scarce. Under 10 percent PEG, the STI of the 750 gray group climbed to 0.41 from 0.23 in the wild type, while its SSI fell from 1.10 in the wild type to 0.90. The same directional pattern appeared under 20 percent PEG, though with lower STI values overall. Crucially, both the 500 and 750 gray groups posted SSI values below 1 under both stress levels, a statistical signature of lower relative susceptibility than the unirradiated controls and the 250 gray group. In plain terms, the heavier radiation doses appear to have generated a pool of mutants in which drought-resilient individuals are more common.

Individual dry-weight measurements revealed considerable variation among M2 mutants from the 250, 500, and 750 gray lineages, and a principal component analysis built on the full suite of morpho-physiological traits captured 89.5 percent of the total variation in a single two-dimensional view. That analysis cleanly separated entries that maintained their performance under stress from those that collapsed, and it flagged a short list of promising candidates under 10 percent PEG, including mutants labeled 250Gy_2P1, 250Gy_3P1, 250Gy_4P1, and the series 500Gy_1P1 through 500Gy_4P1. These are putative mutants, a deliberately cautious term: they show the phenotype the breeders want, but confirming that the trait is genetically fixed rather than a fluke of the growing environment requires progeny testing and, eventually, molecular validation.

The heritability estimates in the study add an important note of realism. Broad-sense heritability, the proportion of observed variation attributable to genetic differences, ranged from 0.24 to 0.60 during the hydroponic phase and from 0.11 to 0.80 during the post-hydroponic greenhouse evaluations at 60 and 90 days. The lower end of those ranges, particularly the 0.11 figure, signals that some measured traits are heavily influenced by environment and would make unreliable selection targets on their own. This is precisely why the authors frame their hydroponic PEG platform as a preliminary screening framework rather than a definitive test: it is designed to narrow thousands of candidates down to a manageable number that can then be subjected to multi-generation and multi-location trials.

The broader significance of the work lies in the pairing of two technologies that are individually old but jointly underused. Mutation breeding with gamma rays has produced improved crop varieties for decades, from rice to barley, because it generates novel allelic variation without the regulatory complexity of transgenic methods. Hydroponic PEG screening, meanwhile, gives breeders a fast, cheap, and controllable way to impose drought stress at scale. Combining them, and wrapping the whole effort in quantitative indices and multivariate statistics, turns what could be a fishing expedition into a structured pipeline. For a forage crop like L. tarramba, which supports livestock systems across dry tropical regions where improved varieties are scarce, even modest gains in drought tolerance could translate into more reliable fodder supplies.

There remain clear caveats. PEG-induced osmotic stress captures only part of what drought means in the field; it does not reproduce the soil physical constraints, the progressive drying cycles, or the atmospheric vapor pressure deficits that real droughts impose. The authors themselves emphasize that the promising M2 lines identified here, including the 250 and 500 gray derivatives that held their growth under moderate stress, must now move into progeny testing and molecular characterization to confirm that the tolerance traits are heritable and to locate the underlying mutations. But as a first filter, the study demonstrates that a tank of PEG-laced nutrient solution, a cobalt-60 source, and a well-chosen set of indices can rapidly surface candidate plants worth a breeder’s attention. In a warming world where forage crops face increasingly erratic rainfall, that kind of accelerated triage may become one of the most valuable tools in the plant breeder’s kit.

Subject of Research: Screening gamma-induced Leucaena tarramba mutants for drought tolerance using PEG-simulated osmotic stress in hydroponics

Article Title: Screening gamma-induced Leucaena tarramba mutants for drought tolerance under PEG-simulated osmotic stress in hydroponics

Article References: Khaerani, P. I., Hastilestari, B. R., Musa, Y., Utamy, R. F., Cai, G., Álvarez-Holguín, A., Indriatama, W. M., Husni, A., Wakano, F., Ashar, J. R., & Anshori, M. F. (2026). Screening gamma-induced Leucaena tarramba mutants for drought tolerance under PEG-simulated osmotic stress in hydroponics. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10008-8

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10008-8

Keywords: Leucaena tarramba, drought tolerance, gamma irradiation, mutation breeding, polyethylene glycol, hydroponics, osmotic stress, M2 mutants, stress tolerance index, heritability, principal component analysis, forage legume