Wood that bonds itself via homologous adhesion through cellulose reconstitution

Abstract

Wood panels are extensively applied in furniture, construction fields, where their versatility and cost-effectiveness make them indispensable, but their assembly relies on adhesives that emit toxic formaldehyde, demand energy-intensive curing, and form weak interfacial bonds. Inspired by wood’s self-repair via cellulose microfibril reorganization, we develop a cellulose-based homologous active adhesive (HAA) derived from wood components. HAA cures under ambient hydration, eliminating toxic emissions and reducing energy consumption by >80%. Its mechanism activates wood surface hydroxyl groups and regenerates cellulose to create a seamless transition layer that enhances load transfer and resistance. This architecture enables specific bonding strength up to 100× greater than conventional adhesives, despite ultra-low solid content (<5%). Using molecular dynamics simulations, AFM nanomechanics, spectroscopy, and life-cycle assessment, we reveal that HAA outperforms commercial resins, offering pot life >30 days, full biodegradability, and >70% lower environmental impacts. HAA establishes a biomimetic, circular pathway for sustainable, high-strength wood bonding.

Most wood adhesives are formaldehyde-based, which is toxic, and requires energy intensive hot-pressing with long curing cycles. Here, the authors develop a cellulose-based homologous active adhesive which cures under ambient hydration, eliminating toxic emissions and reducing energy consumption.

Introduction

The global wood panel industry faces a critical sustainability challenge: meeting rising demand for low-carbon construction materials while addressing concerns over deforestation, timber shortages, and the transition toward a carbon-neutral circular economy^1,2. According to the Food and Agriculture Organization (FAO)^3,4, the annual global demand for wood panels now exceeds 500 million m³, with China accounting for more than 60% of the market (Fig. 1a). Meeting this demand still relies heavily on formaldehyde-based adhesives such as urea-formaldehyde (UF), phenol-formaldehyde (PF), and melamine-formaldehyde (MF) resins, which together represent ~90% of the adhesive market^5,6. Despite advances in engineered wood products, including densified wood, plywood, medium-density fiberboard (MDF), and oriented strand board (OSB), the adhesive bottleneck remains⁷.

Fig. 1. Wood panel industry and principles of homologous active adhesives (HAA).

a Global wood-based panel production by country in 2023. Deeper green in the legend refers to the higher yield. b Comparison of bonding mechanisms: traditional formaldehyde-based resins rely on passive adhesion, whereas HAA achieves homologous active adhesion through cellulose interactions. The synthetic resin: red triangle; hydroxyl (−OH): orange dot; ether bond (−O−): gray dot; inactive cellulose: brown chair shape; activated cellulose: green chair shape; regenerated cellulose: cyan chair shape. c Performance advantages of HAA (blue line) over common market adhesives (PVAc) (pink line), MF (purple line), UF (green line), PF (red line)), including lower solid content, extended pot life, reduced energy consumption, higher specific strength, elimination of formaldehyde (FA) emissions, and competitive product costs. d Life cycle assessment (LCA) comparison of four adhesives (HAA: blue column, MF: green column; UF: pink column; PVAc: orange column) across 12 environmental impact categories (left), and relative contributions of different production stages (right). Categories include terrestrial acidification potential (TAP), global warming potential (GWP), freshwater ecotoxicity potential (FETP), marine ecotoxicity potential (METP), terrestrial ecotoxicity potential (TETP), fossil fuel depletion potential (FFP), human toxicity potential (cancer, HTPc; non-cancer, HTPnc), ozone depletion potential (ODP), photochemical oxidant formation (human health, HOFP; terrestrial ecosystems, EOFP), and water consumption potential (WCP).

Conventional wood adhesives present three fundamental limitations: (i) toxic emissions, (ii) energy-intensive processing, and (iii) weak interfacial bonding. Formaldehyde-based resins have long been criticized for releasing carcinogenic gases that pose chronic health risks^8–10. Their application also requires energy-demanding hot pressing (120–200 °C) and long curing cycles, significantly increasing energy consumption^11,12. Most critically, these adhesives rely on passive mechanical interlocking: viscous polymers that only partially penetrate wood micropores, producing weak, fracture-prone interfaces due to chemical incompatibility between synthetic and natural polymers (Fig. 1b, top)^13,14. This not only compromises bond strength and durability but also necessitates higher material and energy inputs, further worsening sustainability concerns.

We recently reported an alternative strategy based on the oxidation and densification of wood, where fiber cell walls were firmly locked through hemiacetal linkages and hydrogen bonding between cellulose fibrils, yielding a densely packed multilayered structure without the need for interfacial adhesives or binders¹⁵. This adhesive-free system, achieved by bulk oxidation and densification, produced strong and transparent all-biobased glazes. Unfortunately, it is restricted to lamination processes, requiring two or more layers of thin wood sheets or veneers that can be laminated. Another approach was recently demonstrated by Zhang et al., in which wood pulp was dissolved in ionic liquid solutions, introduced at the bonding line, and cured through hot pressing, followed by rinsing and regeneration to produce strong wood adhesion¹⁶.

These advances highlight a broader trend toward cellulose-based adhesion strategies^15–18. Particularly relevant to our work is a system that produced regenerated cellulose films from bamboo parenchyma cells dissolved in N,N-dimethylacetamide (DMAc) with LiCl¹⁹. In this system, coordination of DMAc ligands with Li⁺-Cl⁻ ion pairs facilitated complexation with cellulose chains²⁰. Building on this solvent chemistry, we applied it to expose cellulose fibrils embedded in the cell walls of discarded wood, sawdust, other wood wastes, as well as wood bulk surface, thereby enabling the formation of strong hydrogen-bonded networks and healing across interfaces after cellulose regeneration²¹.

This latter work draws direct inspiration from trees themselves, where wood achieves self-repair and reinforcement naturally through the reorganization of cellulose microfibrils within its cell walls^22,23. Building on these advances, we now introduce a cellulose-based homologous active adhesive (HAA), derived entirely from dissolved wood components, including waste streams. In this work, we precisely define homologous adhesion as a bonding mechanism in which the applied adhesive shares the same chemical and structural origin as the adherend. Unlike biomimetic strategies that often employ synthetic polymers to imitate biological functions, our approach directly utilizes native biological building blocks (Fig. 1b, bottom). Unlike ionic-liquid systems, HAA eliminates the need for high-temperature hot pressing. It further simultaneously activates wood surfaces and regenerates cellulose in situ under aqueous conditions, e.g., HAA creates a seamless homologous transition zone without a discrete adhesive interface, a distinct adhesion mechanism that more closely reflects wood’s intrinsic chemistry.

The HAA process does not leave toxic chemicals on the products while reducing energy demand by more than 80% compared to conventional thermosetting resins, effectively transforming adhesion into an ecological process that contributes to wood circularity. More specifically, HAA directly addresses the core mechanical limitation of conventional adhesives by actively engaging with the wood substrate. Through the contribution of surface hydroxyl groups, the proposed adhesion activates the supramolecular architecture of wood, enabling polymer expansion and molecular-scale interlocking (Fig. 1b, bottom). This structural entanglement creates a robust transition layer of cellulose-rich regions, surpassing the inherent weaknesses of passive adhesives that most frequently rely on van der Waals forces.

Results

When benchmarked against commercial adhesives such as polyvinyl acetate (PVAc), MF, UF, and PF resins, HAA’s active binding strategy produces a bulk domain of wood homologs, comprising activated wood surfaces, penetrated and regenerated cellulose, and lignin, without incompatibility-induced fracture interfaces. The result is a specific bonding strength up to 100 times higher than that of traditional adhesives (Supplementary Fig. 1). Alongside these performance gains, HAA offers clear sustainability advantages, including extended pot life, low solid content, and inherent biodegradability, aligning seamlessly with circular economy principles (Fig. 1c and Supplementary Table 1)^24–30. Given the high cost of the DMAc/LiCl system and the environmental issues associated with organic solvents, solvent recovery is crucial. We exposed 20.0 g of HAA to a high-humidity environment (~90% relative humidity). Under these conditions, HAA regenerated, and the gel began to shrink (Supplementary Fig. 2a). During this process, DMAc was displaced from the gel matrix. After collection and dehydration, the extracted liquid was confirmed to be recyclable DMAc (Supplementary Fig. 2b).

A quantitative life cycle assessment (LCA) further validates HAA’s environmental superiority. Across 12 categories, HAA shows a >70% reduction in cumulative environmental impact relative to MF, UF, and PVAc adhesives, with particularly marked improvements in human toxicity (HTPc), global warming potential (GWP), and fossil fuel depletion (FFP) (Fig. 1d). This advantage arises from replacing petrochemical feedstocks with wood-derived components (reducing raw material impacts by >90%) and eliminating energy-intensive curing (saving >80% in processing energy, equivalent to 39 million GJ/year globally at current production levels)³¹.

Our HAA is synthesized through a streamlined process that begins with mild delignification of wood residues and wastes (D-wood), followed by N,N-dimethylacetamide (DMAc) activation and subsequent dissolution in DMAc/LiCl (Fig. 2a). The color intensity of the resulting HAA solution correlates with cellulose concentration (Supplementary Fig. 3). Dissolution saturates at 4 wt%, beyond which undissolved cellulose appears (Supplementary Fig. 4), providing a clear quality-control marker for HAA synthesis. The viscosity of HAA can be precisely tuned by adjusting the concentration of dissolved wood residues (Supplementary Fig. 5). This tunable, drip-free viscosity enables localized adhesive application on complex surface geometries, thereby optimizing material usage and bonding efficiency. In contrast, low-viscosity DMAc/LiCl solutions tend to drip uncontrollably when applied to wood surfaces (Supplementary Fig. 5). Maintaining this tailored viscosity profile ensures adhesive localization while avoiding performance losses that arise when exceeding the dissolution limit, where excess cellulose disrupts.

Fig. 2. Mechanical properties of HAA-reconstituted wood.

a Schematic of the active bonding process of plywood veneers using HAA. b Tensile strength and elastic modulus of HAA as a function of mass fraction (tensile strength: blue column; elastic modulus: yellow column, error bar: SD of three parallel sample tests). The dotted line indicates the minimum industrial bonding strength requirement (0.7 MPa³³). c In-plane shear performance: a bonded specimen lifting a 250 N load. d Out-of-plane bonding performance: (top) a specimen lifting a 20-N weight; (bottom) reconstituted wood maintaining strength with a small joint contact area. e Bonding strength of wood joined along different cutting directions: radial–radial (R–R, blue column), cross–cross (C–C, green column), and radial–cross (R–C, yellow column) (error bar: SD of three parallel sample tests). f Bonding strength of HAA-reconstituted plywood under dry and wet conditions, and at –30 °C, 25 °C, and 100 °C (wet strength: dark blue column; dry strength: bright blue column, error bar: SD of three parallel sample tests). g Storage stability of HAA, showing bonding strength of HAA-reconstituted plywood after different storage times (tensile strength: blue column; maximum force: green column, error bar: SD of three parallel sample tests). The dotted line indicates the industrial standard threshold (0.7 MPa). h Demonstration of nearly traceless repair in reconstituted wood panels (50 × 30 × 1.5 cm). i Photograph of the scale-up production of HAA. j Large-scale reconstituted panel (150 × 25 × 1.5 cm). k Application in repairing small wooden objects such as antiques.

HAA achieves self-adhesion of wood substrates into plywood products through homologous cellulose interactions (Figs. 1b and 2a), mimicking the natural growth of wood in three synergistic phases. First, DMAc/LiCl activates the wood surface by disrupting its microstructure and exposing hydroxyl groups, markedly enhancing wettability and reactivity. Unlike conventional adhesives, which suffer from poor interfacial compatibility, the homologous composition of HAA offers a distinct advantage. Second, cellulose chains in HAA intertwine with the activated wood surfaces, forming a dense hydrogen-bonded network that establishes immediate adhesion within 30 minutes. Finally, under ambient moisture, dissolved cellulose undergoes interphase diffusion, solvent exchange (DMAc to water), and hydrogen-bond reorganization, ultimately solidifying into a high-strength, seamless bond without a discernible interface (Supplementary Figs. 6 and 7).

Building on this mechanism, we propose that HAA achieves true circularity by incorporating wood cell walls, cellulose-rich regions, and regenerrated cellulose, effectively transforming panel production residues and wastes into high-value binding resources within a closed-loop paradigm. This resource-efficient approach, coupled with life cycle assessment (LCA) validation, highlights HAA’s distinctive environmental superiority over conventional adhesives (UF, MF, PVAc). Quantitative LCA results reveal drastic reductions in global warming potential, significantly lower than UF and exceeding 99% reductions compared with MF and PVAc, underscoring HAA’s dual significance: enabling carbon-neutral manufacturing while establishing circular resource flows.

HAA-reconstituted wood exhibits extraordinary performance across multiple metrics, including mechanical strength, environmental resilience, shelf stability, long-term durability, and even optical appearance, surpassing common regulatory standards and often outperforming the original wood components.

Mechanical testing of HAA-reconstituted assemblies revealed a concentration-dependent evolution. Bilayer plywood (Supplementary Fig. 8) exhibited a tensile strength of 0.85 MPa at 2.5 g/100 g HAA, already exceeding the requirements of the Chinese National Standard GB/T 9846-2015 (Fig. 2b)^32,33. Maximum strength (1.42 MPa) occurred at 4.0 g/100 g, beyond which further increases in concentration provided negligible gains. Furthermore, the soaking time of the HAA-reconstituted wood specimens in water also affected their tensile strength. After only 0.5 h of soaking, the tensile strength reached 0.74 ± 0.11 MPa, easily exceeding the standard requirements. When the soaking time reaches 2 h, the mechanical properties of HAA-reconstituted wood tend to stabilize; therefore, the soaking time for HAA-reconstituted wood is 1–2 h (Supplementary Fig. 9).

The optimal dosage corresponds to the formation of a dense transition layer comprising a continuous percolation network of regenerated cellulose (Supplementary Fig. 10). Here, interfacial bonding saturates through fibril entanglement with wood-activated cellulose. This layer acts as the primary load-bearing region, while excess cellulose contributes little additional reinforcement. Elastic modulus measurements reflect this process: initial densification yields higher modulus values, followed by stabilized strain accommodation. SEM fracture images (Supplementary Fig. 11) further support this mechanism, showing the transition layer’s central role in stress transfer and the limited role of excess cellulose fibrils.

HAA-reconstituted wood demonstrates outstanding strength across diverse loading scenarios. In-plane shear tests showed that a mere 1 mg of adhesive can sustain a shear force of 250 N (107 times its self-weight; Fig. 2c). In out-of-plane configurations, bonded plywood retained a 2-kg load on a minimal contact area (~6.25 × 10⁻⁴ m², Fig. 2d, top). Combined with precise deposition control from its viscous flow, HAA achieves robust bonding on irregular geometries such as angular joints, while preserving structural integrity (Fig. 2d, bottom). These results demonstrate stress distribution comparable to, or even surpassing, structural epoxies³⁴.

Unlike traditional biomass-based adhesives, HAA overcomes directional and material constraints inherent to wood bonding. It enables rapid adhesion under ambient conditions across diverse wood types and cutting directions, eliminating the need for hot pressing or cell alignment. Mechanical failures consistently occurred within the wood itself (cohesive fracture) rather than at the adhesive interface, confirming superior interfacial strength (Fig. 2e and Supplementary Figs. 12 and 13). Even hot pressing (65–105 °C) had a negligible effect on bonding strength (Supplementary Fig. 14a), highlighting the robustness of hydrogen bonding and fibrillar entanglement between dissolved and activated cellulose. Beyond plywood, HAA readily bonded wood powder and particles via simple mixing and washing (Supplementary Fig. 14b, c), demonstrating exceptional processing flexibility. Similarly, HAA can be successfully used to bond multilayer boards (Supplementary Fig. 15a), achieving excellent mechanical properties. In particular, the breaking strength of a 5-layer board reaches an impressive 41.58 ± 0.67 MPa (Supplementary Fig. 15b).

The homologous nature of HAA endows plywood with remarkable environmental resilience. Traditional adhesives form heterogeneous bonds, which undergo differential dimensional changes under thermal or humid conditions, inducing stresses that lead to cracking and delamination^35,36. In contrast, HAA maintained bonding strength of ~1.5 MPa across a wide temperature range (−30 to 100 °C; Fig. 2f). It also sustained >1.2 MPa in both dry and wet states, outperforming all reported bio-based adhesives^37,38 and far exceeding the 0.7 MPa industry standard (Fig. 2f)³³. This stability arises because HAA eliminates the interfacial mismatch through compositional homology, allowing the adhesive and wood substrate to respond in a synchronized way to changes in temperature and humidity. At the molecular level, dynamic reconfiguration of hydrogen bonds among cellulose components continuously redistributes stresses, while the underlying covalent network remains intact. More importantly, unlike many existing biomass adhesives that strictly require energy-intensive hot-pressing processes^{12,33,39–42}, HAA achieves this robust bonding performance at ambient conditions (Supplementary Table 2).

Shelf-life stability is equally remarkable. Unlike conventional trialdehyde-based glues, HAA retains satisfactory adhesive properties after being stored at ambient conditions for 7 months (Tensile strength of HAA-reconstituted wood is 0.99 MPa and 606.76 N maximum force, both exceeding national standards; Fig. 2g). Similarly, we measured the tensile strength of HAA-reconstituted wood specimens that had been stored under ambient conditions for 2, 4, and 6 months to investigate the long-term performance of the HAA-reconstituted wood. After 2 months of storage, the tensile strength of the HAA-reconstituted wood was 1.38 MPa; even after 6 months of ambient storage, the tensile strength remained robust at 1.35 MPa. These results clearly indicate that the final wood products bonded with HAA maintain highly stable and reliable mechanical performance during long-term storage (Supplementary Fig. 16). Their specific strength reached 6.31 MPa·g⁻¹·m⁻², representing a 100-fold improvement over traditional adhesives at significantly lower loading levels (Supplementary Figs. 1 and 17).

The nearly invisible bonding interface enables traceless repair of high-value wooden antiques (Fig. 2h, k). HAA is also readily scalable: batches of >20 kg were produced within two days using a 10 L reactor (Fig. 2i), and the overall economics of large-scale HAA production were calculated. The comprehensive unit cost of HAA is estimated to be ~$0.6467 per kg, which is lower than that of many conventional commercial wood adhesives (Supplementary Tables 3 and 4). In addition, large panels (150 × 25 cm) were successfully bonded without visible deformation (Fig. 2j).

The water-based process minimizes damage to original wood while offering operational versatility. Comparable performance was obtained using deionized, potable, or municipal water. Moreover, the aqueous solution can be recycled through at least five reuse cycles without loss of clarity, underscoring both economic and environmental advantages with minimal post-process pollution. (Supplementary Fig. 18). Indeed, the preparation strategy for HAA exhibits excellent source materials universality. The tensile strength of the specimens bonded with HAA derived from biomass residues (bamboo, wheat straw), and recycled paper reached 1.38, 1.33, and 1.41 MPa, respectively (Supplementary Fig. 19). These results demonstrate that a wide variety of cellulose sources can be effectively converted into HAA and successfully applied in wood reconstitution.

Analyses following National Renewable Energy Laboratory (NREL) protocols were used to quantify compositional variations of HAA^43–46. Delignified wood (D-wood) contained 94.57 wt% cellulose, 3.20 wt% lignin, and 2.00 wt% hemicellulose, in contrast to natural wood with 55.13, 37.43, and 7.03 wt%, respectively (Supplementary Table 5). The enriched cellulose content ensures high hydrogen-bonding density and strong interfacial cohesion, governing the physicochemical properties of the transition layer.

HAA fundamentally reconfigures the wood-adhesive interface through surface activation and dissolved cellulose interactions. Unlike traditional adhesives, this process generates a continuous hydrogen-bonding-reinforced transition layer (Fig. 3a). Strong adhesion depends on wettability and penetration depth, which follow cellulose percolation dynamics. Ultra-depth-of-field microscopy showed that penetration depth decreases from 121.13 μm to 90.14 μm as concentration increases (Fig. 3b and Supplementary Figs. 20 and 21).

Fig. 3. Mechanism of the HAA bonding process.

a Schematic of the characteristic transition region formed by HAA. b Ultra-depth-of-field microscopy images of wood reconstituted with HAA at cellulose concentrations of 2.0 g·100 g⁻¹ and 4.0 g·100 g⁻¹, scale bar = 5 mm. c Micro-FTIR images showing the distribution of cellulose at 3454 cm⁻¹ across the transition region, including native wood cell walls, cellulose-rich zones, and regenerated cellulose regions. d₁ Schematic of SEM viewing directions for natural wood. d₂ SEM image of the transition region in cross-cut wood scrimber, scale bar = 500 μm. d₃ SEM images of the transition region in longitudinal-cut wood scrimber (red box: the magnified area of the SEM image), scale bar = 500 μm and 100 μm. e₁ Schematic of SEM viewing directions for delignified balsa wood. e₂ SEM image of the transition region showing banded cellular structures between D-wood and regenerated cellulose (red box: the magnified area of the SEM image), scale bar = 500 μm and 100 μm. e₃ SEM image of regenerated cellulose, scale bar = 5 μm.

At low concentrations, deep penetration occurs due to low viscosity (Supplementary Fig. 5), but uneven activation and loose fibril entanglement lead to cracks. In contrast, the optimal 4.0 wt% formulation achieves shallower yet complete penetration, enabling formation of a dense and continuous cellulose network (Supplementary Fig. 21).

Three synergistic effects drive this optimum: (1) uniform substrate coverage ensures consistent cellulose activation; (2) optimized fibril density enhances hydrogen-bond percolation; (3) controlled viscosity enables precise interfacial architecture. Thus, maximum bond strength emerges when penetration depth is constrained enough to promote the development of a 3D cellulose network while maintaining complete wetting.

Micro-FTIR confirmed the formation of a triphasic gradient architecture of homologous cellulose within the transition layer (Fig. 3c). The central blue region (HAA-depositing zone) contained nearly 100% cellulose. Surrounding light blue/green zones represented cellulose-rich regions from wood surface activation, while the red areas corresponded to native cell walls (~50% cellulose).

Spectral variations at 3454 cm⁻¹ revealed enhanced O–H stretching and C–H bending vibrations, confirming progressive cellulose enrichment from wood to cellulose-rich regions and further to regenerated cellulose (Supplementary Fig. 22)^37,38,47.

SEM imaging revealed the continuum of cellulose at the bonding region (Fig. 3d, e). Samples sectioned transversely and longitudinally (Fig. 3d₁) showed a dense fibrous structure at the interface, with cellular conduit pores visible above and below. In transverse view, regenerated cellulose seamlessly bridged wood lumina (Fig. 3d₂), while longitudinal sections displayed cellulose nanofibrils templating along native cell walls, eliminating any discernible boundary parallel to the lumen (Fig. 3d₃).

To visualize spatial distribution, delignified balsa wood was sliced parallel to the lumen (Fig. 3e₁). SEM revealed distinct regenerated cellulose bands tightly bound to cell walls (Fig. 3e₂), with significant accumulation near cellulose-rich regions (Fig. 3e₃, Supplementary Fig. 23). These results confirm that HAA forms a cellulose transition zone within the wood through water-mediated interfacial entanglement, enabling molecular-level reorganization of the structure while ensuring strong adhesion to the native cellulose matrix.

HAA’s wood reconstitution mechanism occurs through two synergistic stages: Wood surface activation via DMAc/LiCl coordination chemistry and cellulose entanglement and regeneration (Fig. 4a)^19–21:

Fig. 4. Mechanism of the wood reconstitution process.

a Schematic of the two main stages: wood surface activation, followed by cellulose entanglement and regeneration. b Free energy changes of cellulose in water versus DMAc/LiCl (water: red hollow circle, DMAc/LiCl: blue solid cube), showing structural stability in water and dissociation in the solvent system. c Molecular dynamics analysis of hydrogen bond number and contact atoms during the reconstitution process for AC–DC and AC–AC interfaces (hydrogen bonds: blue line, contact atoms: green line). d SEM image of natural wood cells. e SEM images of wood cells after treatment and of reconstituted wood (magnified area of the SEM image). Scale bars: 10 μm (d), 10 μm and 3 μm (e).

Stage 1: Surface Activation by DMAc/LiCl. In the first stage, Li⁺ forms [DMAc-Li]⁺ complexes that disrupt cellulose crystallinity, while Cl⁻ ions interact with cellulose hydroxyl groups to weaken intermolecular hydrogen bonds. This dual action enables DMAc to solvate cellulose chains across both amorphous and crystalline regions (Supplementary Fig. 24)^20,21,48.

Molecular dynamics (MD) simulations confirmed the thermodynamic feasibility of this process. Free energy calculations showed cellulose has higher stability in water (ΔG₁ = –1.83 kcal/mol) but reduced stability in DMAc/LiCl (ΔG₂ = +5.71 kcal/mol) (Fig. 4b, Supplementary Figs. 25–27, and Supplementary Tables 6 and 7). The adsorption free energy difference of 7.54 kcal/mol, equivalent to ~20× RT ( ≈ 0.6 kcal/mol at 300 K), corresponds to a ~10⁶-fold change in the equilibrium constant. This implies dramatically shorter residence times for cellulose strands on crystallite surfaces in DMAc/LiCl compared with water, driving spontaneous dissolution upon solvent exchange (Fig. 4a).

Crucially, DMAc/LiCl plays a dual role: dissolving wood residues for HAA synthesis while partially dissolving cell walls to expose cellulose. Comparative characterizations confirmed this activation: (1) Microscopy showed reduced structural definition in treated wood compared with the well-preserved architecture of natural wood. (2) Fluorescence spectroscopy revealed enhanced emission intensities at 433.9 and 468.1 nm under UV excitation, consistent with cellulose exposure. (3) SEM imaging displayed deconstructed cell corners and regenerated cellulose bundles in regenerated samples (Fig. 4d, e and Supplementary Fig. 28).

Together, these results confirm that DMAc/LiCl induces distinct morphological modifications that prime wood surfaces for interfacial reconstruction.

Stage 2: Water-Driven Entanglement and Regeneration. Surface activation enables Stage 2, in which water triggers self-assembly through hydrogen bonding between surface-activated cellulose (AC) and dissolved cellulose (DC) in HAA (Fig. 4a). This process forms a cellulose-rich interfacial zone that bridges regenerated cellulose with the native structure, allowing simultaneous entanglement and hydrogen bond reorganization (Supplementary Fig. 29).

MD simulations showed the AC–DC interface involves ~1150 atoms and ~15 persistent hydrogen bonds over 300 ns, compared with <700 atoms and only 3–4 bonds in AC–AC contacts (Fig. 4c). Interaction persistence was also threefold higher for AC–DC (300 ns vs. 100 ns for AC–AC), enabling formation of a structurally ordered, regionally oriented adhesive layer. These findings demonstrate that wood reconstitution primarily occurs through AC–DC entanglement, with AC–AC contacts providing secondary stabilization.

Spectroscopic data further validated this mechanism. FTIR showed intensified C–O stretching at 1025 cm⁻¹ (confirming cellulose exposure) and diminished O–H stretching at 3353 cm⁻¹ (reflecting hydrogen bond consumption) (Supplementary Fig. 30).

Together, these results establish HAA’s reconstitution as a thermodynamically guided cascade: solvent-enabled surface activation followed by water-driven, preferential AC–DC entanglement. This mechanism yields a hierarchical interfacial architecture that integrates regenerated and native cellulose into a seamless, high-strength adhesive bond.

AFM nanomechanics mapping revealed three distinct structural domains in HAA-reconstituted wood (Fig. 5a). Force–distance analysis distinguished these domains based on adhesion forces and Young’s moduli (Fig. 5b and Supplementary Fig. 31): (1) Cellulose-rich adhesive region—low adhesion, intermediate modulus. (2) Transitional regenerated cellulose region—low adhesion, high modulus; and (3) Native wood bulk—high adhesion, low modulus^49–51.

Fig. 5. AFM analysis of HAA-reconstituted wood.

a Schematic of AFM tip interaction with wood and corresponding AFM image of reconstituted wood (scale bar, 200 μm): I: regenerated cellulose region, II: cellulose-rich region, III: wood region. b Representative force–distance curves for native wood, the cellulose-rich region, and regenerated cellulose (yellow line and pattern: wood region, green line and pattern: cellulose-rich region, blue line and pattern: regenerated cellulose region). c–e AFM topographical images showing distinct arrangements of regenerated cellulose, cellulose-rich regions, and native wood (scale bar, 1 μm). f Histograms of adhesion forces measured on wood, cellulose-rich regions, and regenerated cellulose (yellow line and column: wood region, green line and column: cellulose-rich region, blue line and column: regenerated cellulose region). g Schematic illustration of interphase-enhanced wood bonding through HAA.

These mechanical contrasts arise from structural reorganization: tightly packed regenerated cellulose in regions I and II versus lignin/hemicellulose-softened native wood in region III. Unlike conventional adhesives, which form sharp and often weak interfaces, HAA creates a non-covalent, self-assembled gradient that extends more than 50 μm into the wood bulk without a distinct boundary. This smooth transitional region underpins the long-term stability and mechanical robustness of HAA- reconstituted wood.

AFM topography further quantified the continuum by visualizing both native wood and regenerated cellulose regions (Fig. 5c–e). Native wood maintained a relatively homogeneous rough micromorphology, while the regenerated cellulose region exhibited pronounced chunky features with large height variations, likely reflecting inhomogeneous regeneration. The transitional interfacial zone (II) displayed mixed morphologies across a considerable depth, confirming a broad gradient layer rather than a sharp interface.

Adhesion force mapping reinforced this interpretation, showing interfacial regions with values intermediate between native wood (4.2 nN) and regenerated cellulose (15.1 nN) (Fig. 5f and Supplementary Figs. 32 and 33). These graded adhesion profiles directly correlate with the observed structural transition.

Collectively, AFM-derived nanomechanical data confirm that HAA bonding generates a three-region continuum: native wood’s random fibril distribution, a transitional gradient zone, and regenerated cellulose’s more ordered architecture (Fig. 5g). The interfacial region emerges as a distinct phase formed through structural reorganization, rather than a simple mixture of components, highlighting its critical role in the stability of HAA-reconstituted wood.

Discussion

Cellulose-based homologous active adhesive (HAA) redefines wood bonding by leveraging the intrinsic material affinity of adhesive and substrate. Unlike passive conventional adhesives, HAA enables autonomous, high-strength adhesion through homologous cellulose interactions, seamlessly integrating with wood substrates to form plywood and reconstituted products. This mechanism allows rapid ambient bonding across diverse wood types and cutting directions, and even binds sawdust through simple mixing and washing.

The resulting HAA-reconstituted wood exhibits exceptional multiaxial strength, consistently surpassing standards, owing to the formation of a pervasive regenerated cellulose network within the adhesive zone. Molecular dynamics simulations elucidate the mechanism: solvent-assisted partial dissolution activates wood-surface cellulose fibrils, which interlace with HAA’s dissolved cellulose; subsequent aqueous-phase hydrogen bonding drives regeneration and structural reconstitution, producing optimized cellulose-rich transition zones. Critically, maximum bond strength arises when HAA’s self-limiting penetration depth promotes full 3D network development while maintaining complete substrate wetting, a self-regulating feature absent in synthetic adhesives. By integrating green sourcing, active homologous binding, and microstructural precision, HAA establishes a transformative framework for sustainable wood restructuring and a viable alternative to petrochemical-based adhesives.

Methods

Materials and chemicals

Wood samples, including basswood and balsa wood, were purchased from Hangzhou Alibaba Co. Ltd. The raw basswood material consisted of thin chips with a thickness of 0.5 mm. For mechanical testing, the dimensions of the basswood and balsa wood specimens were prepared as blocks of 100 mm × 25 mm × 3 mm (longitudinal × tangential × radial). Hydrogen peroxide (H₂O₂, 30 wt%) and ethanol (analytical reagent grade) were obtained from Tianli Chemical Reagent. Deionized water was used throughout the wood regeneration process. N,N-dimethylacetamide (DMAc, >99%), acetic acid (CH₃CO₂H, >99%), and lithium chloride (LiCl, ACS reagent, ≥99%) were purchased from Shanghai Aladdin Biochemical Technology.

Preparation of HAA

Partial delignification of raw materials was performed using a hydrogen peroxide-based method. Basswood chips (10 g, 0.5 mm thickness, aligned with the growth direction) were boiled in 100 mL of peracetic acid solution, prepared by mixing 30% hydrogen peroxide and acetic acid at a 2:1 (v/v) ratio, at 80 °C for 2 h. This treatment partially removed lignin and hemicellulose. The resulting delignified wood samples (D-wood) were thoroughly washed with deionized water and ethanol until neutral pH (~7) was reached, and then dried at room temperature for 2 days. For HAA preparation, the D-wood was first immersed in DMAc/LiCl solvent and subsequently dissolved in DMAc/LiCl (8 wt% LiCl) under continuous stirring to obtain the cellulose-based homologous active adhesive (HAA).

Reconstitution of wood using HAA

For the HAA reconstitution process, 0.9 mg of HAA was applied to two basswood boards (100 mm × 25 mm × 3 mm) over a coating area of 25 mm × 25 mm. The coated boards were joined, clamped together, and immersed in deionized water. After 30 min, the samples were removed and dried at room temperature for 2 days, completing the reconstitution process.

Characterizations

The morphology and structure of wood samples and plywood were examined by scanning electron microscopy (SEM, Apreo S HiVac, Thermo Scientific, USA). The morphology and distribution of the wood substrate and adhesive layer were observed using an optical microscope (MP41, Mshot, China) and an ultra-depth three-dimensional microscope (VHX-6000, KEYENCE, Japan). The rheological behavior of HAA at different mass fractions was measured with a rheometer (AR2000ex, TA Instruments).

Chemical functional groups were analyzed by Fourier-transform infrared (FTIR) spectroscopy (Nicolet iS10, Thermo Scientific, USA) in the wavelength range of 400–4000 cm⁻¹. Crystal structures were determined by X-ray diffraction (XRD, Ultima IV, Rigaku, Japan) at a scanning rate of 4° min⁻¹ over the 2θ range of 5°–80°. Tensile properties of wood samples were evaluated using a universal testing machine (UTM2503, Suns) at a constant crosshead speed of 5 mm min⁻¹.

Fluorescence spectra were collected with a photoluminescence spectrometer equipped with a xenon lamp (FLS-1000, Edinburgh Instruments, UK), using an excitation wavelength of 365 nm and a scanning range of 385–800 nm. Nanomechanical tests were performed with an atomic force microscope (AFM, Jupiter XR, Oxford Instruments, Santa Barbara, USA) equipped with a silicon tip (AC160) in force mapping mode. All photographs were recorded using HUAWEI smartphones.

Author contributions

Conceptualization: L.B.; methodology: Y.S.; investigation: Y.S. and L.B.; visualization: Y.S., Y. Liu (Yang Liu), Z.W., Z.Y., and L.Y.; supervision: S.L., C.W., S.H., Z.L., Y.L. (Yi Lu), and O.J.R.; writing—original draft: Y.S. and L.B.; writing—review and editing: Y.S., S.H., Y.L., and O.J.R.

Peer review

Peer review information

Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work. A peer review file is available.

Data availability

All data are included in this article and its Supplementary Information. All data underlying this study are available from the corresponding author Siqi Huan upon request. Source data are provided with this paper.

Competing interests

The authors declare no competing interests.

Supplementary information

The online version contains supplementary material available at 10.1038/s41467-026-72609-z.