Emulsions are everywhere in modern life, quietly holding together the foods we eat, the cosmetics we smooth onto our skin, and the medicines we swallow. Yet the molecular surfactants that traditionally stabilize these mixtures of oil and water carry well-known drawbacks. Compounds such as Tween-80, Span 80, and cetyltrimethylammonium raise toxicity and biocompatibility concerns, and because thermal motion constantly jostles them, they can detach from interfaces and allow droplets to merge. A new review published in Advances in Industrial and Engineering Chemistry by researchers at Sungkyunkwan University argues that a humble material derived from plants, nanocellulose, could offer a superior and sustainable alternative, provided scientists learn to engineer its surfaces with precision.
The review, led by Jongryeol Yang, Haeun Kwon, Dawon Jeong, and Jin Woong Kim, surveys recent advances in what the authors call nanocellulose interface engineering. Their central message is that cellulose nanocrystals and cellulose nanofibrils, the two principal forms of nanocellulose, already possess the raw ingredients for exceptional emulsion stabilization: natural abundance, biodegradability, high aspect ratios, controllable wettability, and remarkable mechanical strength. What they lack, in their native state, is sufficient hydrophobicity to anchor themselves firmly at oil-water interfaces. The paper describes a growing toolbox of chemical and physical strategies designed to overcome this limitation and unlock applications in pharmaceutical delivery, food preservation, and cosmetic formulation.
To understand why particles can outperform molecules at stabilizing emulsions, the authors turn to a classic piece of colloid science. The adsorption energy of a spherical particle at an oil-water interface follows the relationship E = πr²γ(1 ± cosθ)², where r is the particle radius, γ is the interfacial tension, and θ is the contact angle the particle makes with the interface. Because this energy scales with the square of the particle size, even modest particles experience adsorption energies thousands of times greater than thermal energy, producing what researchers describe as irreversible interfacial anchoring. Once lodged at the boundary between oil and water, a particle essentially cannot be dislodged, which is why Pickering emulsions, named after early twentieth-century observations by Walter Ramsden and Spencer Umfreville Pickering, resist coalescence far better than surfactant-stabilized systems.
Cellulose nanocrystals, or CNCs, present a fascinating paradox. Produced by acid or enzymatic hydrolysis of cellulose fibers, these needle-like particles measure roughly 5 to 20 nanometers across and hundreds of nanometers long, and their surfaces carry negative charges from sulfate groups introduced during processing. That electrostatic repulsion should, in principle, disfavor interfacial adsorption and prevent the close packing needed for robust stabilization. Yet CNCs stabilize emulsions remarkably well, and the review explains why: crystallographic anisotropy. Different crystal faces of a CNC carry different chemistries. The hydrophilic faces, such as the (010) and (110) planes, expose hydroxyl groups and charged species, while the hydrophobic (200) edge planes present minimal polar functionality. When a CNC arrives at an oil-water interface, it orients itself so that its charged faces align with water and its hydrophobic edges dip into the oil, achieving favorable anchoring despite its overall hydrophilic character.
That elegant self-orientation, however, does not solve everything. The same sulfate groups that make CNCs water-soluble also generate intermolecular repulsion that impedes the formation of dense, mechanically strong interfacial networks. One remedy is ionic cross-linking. Simple monovalent salts such as sodium chloride and potassium chloride screen the negative charges, lowering both surface and interfacial tension. More dramatically, divalent metal cations such as zinc nitrate forge genuine cross-links between neighboring nanocrystals. Rheological measurements show that adding divalent metal nitrates transforms CNC suspensions into gel-like materials with enhanced storage and loss moduli, and the resulting three-dimensional networks suppress creaming, aggregation, and coalescence, conferring superior kinetic stability on the emulsions.
Chemical modification offers an even more direct route to better stabilizers. Because cellulose is studded with hydroxyl groups, chemists can graft a wide variety of molecules onto its surface. The review highlights work by Nigmatullin, Xu, and colleagues showing that attaching alkylamine chains of increasing length creates a controlled gradient of surface hydrophobicity. Longer alkyl chains amplify hydrophobic interactions between particles, attenuating electrostatic repulsion and promoting percolated self-associative networks with greater mechanical integrity. Octylamine-modified CNCs substantially reduce surface tension, and cryo-scanning electron microscopy confirms the formation of stable emulsion droplets armored with the modified crystals. In a related approach, Ataeian and colleagues used EDC/NHS coupling chemistry to graft polyamidoamine dendrimers onto CNCs, increasing water contact angles and enabling direct microscopic visualization of how densely the particles assemble on individual droplet surfaces.
Perhaps the most striking demonstration of molecular design comes from Tang and colleagues, who grafted polystyrene chains specifically onto the end groups of CNCs rather than their side surfaces. The result is a surfactant-mimicking architecture in which each particle carries a hydrophilic crystalline body and hydrophobic polymer tails. Emulsions stabilized by these amphiphilic CNCs exhibited exceptional coalescence resistance, maintaining their structural integrity for four months of storage. Such longevity, achieved without any molecular surfactant, illustrates how deliberately engineered particle geometry can rival or exceed conventional emulsifiers while avoiding their toxicity concerns.
Cellulose nanofibrils, or CNFs, behave differently from their crystalline cousins. With diameters of 10 to 50 nanometers and lengths of several micrometers, these flexible filaments do not simply sit at interfaces; they weave them. CNFs form interconnected fibrillary films at oil-water boundaries while simultaneously building three-dimensional networks in the surrounding water, restricting both droplet coalescence and droplet mobility. The review emphasizes that the degree of fibrillation is critical: completely nanofibrillated CNFs adsorb irreversibly onto droplet surfaces and form entanglement networks that raise viscoelastic moduli, whereas incompletely fibrillated material allows droplet deformation and eventual coalescence. Complementary strategies, including TEMPO-mediated oxidation that converts C6 hydroxyl groups into carboxylates and cationic modification with glycidyltrimethylammonium chloride, further tune charge and adhesion, with TEMPO-oxidized CNF emulsions maintaining consistent droplet size distributions for thirty days.
The most advanced engineering targets the remaining weaknesses of CNF films: porosity that lets internal phases leak out, and vulnerability to crystallization-induced destabilization when the encapsulated material is waxy or crystalline. Metal-phenolic network technology addresses the first problem by coating CNF-armored droplets with dense layers of phenolic compounds and metal ions. Park and colleagues validated the mechanism using DLVO theory, showing that the metal-phenolic coating amplifies hydrophobic interaction energies between CNFs and oil droplets, enabling stable emulsions even under low-energy vortexing. The phenolic layer adds antioxidant functionality, protecting oxidatively fragile cargo. For the second problem, metal-organic membranes built from metal cations and organic ligands create comprehensive envelopes around droplets, preventing leakage and confining crystal growth within the droplet interior. These membranes also promote interdroplet association networks that raise bulk viscosity and preserve long-term structural stability, and dual-chain hydrophobically modified CNFs have stabilized high-internal-phase emulsions exceeding 74 volume percent oil.
The authors are candid about the obstacles between laboratory success and industrial reality. Manufacturing nanocellulose at scale remains expensive and energy-intensive, with acid hydrolysis, TEMPO oxidation, and mechanical fibrillation all consuming significant resources, and batch-to-batch variability undermines the reproducibility that commercial products demand. Regulatory frameworks for nanomaterials in food, cosmetics, and pharmaceuticals are still underdeveloped, and comprehensive toxicological data remain scarce. The long-term degradation behavior of nanocellulose-stabilized interfaces under storage conditions is also poorly understood, complicating shelf-life predictions. Still, the review concludes that nanocellulose has already demonstrated remarkable colloidal stability, with reported formulations exceeding one month of ambient storage without phase separation. With greener processing, standardized safety protocols, and scalable formulation design, these plant-derived nanomaterials could transform how industry stabilizes everything from ice cream to injectable drug carriers, replacing a century of surfactant chemistry with engineered wood at the nanoscale.
Subject of Research: Nanocellulose interface engineering for stabilizing Pickering emulsions
Article Title: Advanced nanocellulose interface engineering for Pickering emulsion stabilization
Article References: Yang, J., Kwon, H., Jeong, D., & Kim, J. W. (2025). Advanced nanocellulose interface engineering for Pickering emulsion stabilization. Advances in Industrial and Engineering Chemistry, 1(1), Article 25. https://doi.org/10.1007/s44405-025-00021-0
Image Credits: AI Generated
DOI: 10.1007/s44405-025-00021-0
Keywords: nanocellulose, Pickering emulsions, cellulose nanocrystals, cellulose nanofibrils, interface engineering, emulsion stabilization, surfactants, surface modification, metal-phenolic networks, metal-organic membranes, drug delivery, colloid science
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Bethany Barker. (October 1, 2026). Tiny Wood Whiskers Could Replace Toxic Surfactants in Next-Generation Emulsions. Scienmag. https://scienmag.com/tiny-wood-whiskers-could-replace-toxic-surfactants-in-next-generation-emulsions/
Bethany Barker. “Tiny Wood Whiskers Could Replace Toxic Surfactants in Next-Generation Emulsions.” Scienmag, 1 October 2026, https://scienmag.com/tiny-wood-whiskers-could-replace-toxic-surfactants-in-next-generation-emulsions/. Accessed 1 October 2026.
Bethany Barker. “Tiny Wood Whiskers Could Replace Toxic Surfactants in Next-Generation Emulsions.” Scienmag. October 1, 2026. https://scienmag.com/tiny-wood-whiskers-could-replace-toxic-surfactants-in-next-generation-emulsions/
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Tags: advanced materials for oil-water stabilizationbio-based surfactants for cosmeticsbiodegradable stabilizers for emulsionscellulose nanocrystalscellulose nanocrystals for emulsificationcellulose nanofibrilscolloid scienceDrug deliveryeco-friendly emulsification technologiesemulsion stabilizationinterface engineeringmetal-organic membranesmetal-phenolic networksnanocellulosenanocellulose emulsionsnanocellulose interface engineeringnanocellulose nanofibrils in emulsionsnanocellulose surface modification techniquesPickering emulsionsplant-based surfactant alternativessurface modificationsurfactantssustainable emulsifier developmenttoxicity reduction in emulsions
