A strong and tough supramolecular assembled β-cyclodextrin and chitin nanocrystals protein adhesive: Synthesis, characterization, bonding performance on three-layer plywood

The development of a biomass adhesive as a substitute for petroleum-derived adhesives has been considered a viable option. However, achieving both superior bonding strength and toughness in biomass adhesives remains a significant challenge. Inspired by the human skeletal muscles structure, this study reveals a promising supramolecular structure using tannin acid (TA) functionalized poly-β-cyclodextrin (PCD) (TA@PCD) as elastic tissues and chitin nanocrystals (ChNCs) as green reinforcements to strengthen the soybean meal (SM) adhesive crosslinking network. TA@PCD acts as a dynamic crosslinker that facilitates reversible host-guest interactions, hydrogen bonds, and electrostatic interactions between adjacent stiff ChNCs and SM matrix, resulting in satisfactory strength and toughness. The resulting SM/TA@PCD/ChNCs-2 adhesive has demonstrated satisfactory wet and dry shear strength (1.25 MPa and 2.57 MPa, respectively), toughness (0.69 J), and long-term solvents resistance (80 d). Furthermore, the adhesive can exhibit desirable antimildew characteristics owing to the phenol hydroxyl groups of TA and amino groups of ChNCs. This work showcases an effective supramolecular chemistry strategy for fabricating high-performance biomass adhesives with great potential for practical applications.

Programmable and Shape-Color Synchronous Dual-Response Wood with Thermal Stimulus

Stimuli-responsive materials exhibit huge potential in sensors, actuators, and electronics; however, their further development for reinforcement, visualization, and biomass-incorporation remains challenging. Herein, based on the impregnation of thermochromic microcapsule (TCM)-doped dynamic covalent vitrimers, a programmable shape-color dual-responsive wood (SRW-TC) was demonstrated with robust anisotropic structures and exchangeable covalent adaptable networks. Under mild conditions, the resultant SRW-TC displays feasible shape memorability and programmability, resulting from the rigidity-flexibility shift induced by the glass-transition temperature (34.99 °C) and transesterification reaction triggered by the topology freezing transition temperature (149.62 °C). Furthermore, the obtained SRW-TC possesses satisfactory mechanical performance (tensile strength of 45.70 MPa), thermal insulation (thermal conductivity of 0.27 W/m K), anisotropic light management, and benign optical properties (transmittance of 51.73% and haze of 99.67% at 800 nm). Importantly, the incorporation of compatible TCM enables SRW-TC to visualize shape memory feasibility and rigidity/flexibility switching and respond to the external thermal stimulus through the thermal-induced shape-color synchronous dual-responsiveness, which successfully demonstrates the applications of sensing temperature, grasping objects, encrypting/decoding icon messages, and so on. The proposed facile and highly effective strategy could serve as a guideline for developing high-performance multifunctional wood composite with promising intelligent applications in performance visualization, environmental sensing, materials interactivity, information dual-encryption, local precision shape and color regulation, etc.

Oyster-inspired carbon dots-functionalized silica and dialdehyde chitosan to fabricate a soy protein adhesive with high strength, mildew resistance, and long-term water resistance

Developing multifunctional adhesives with exceptional cold-pressing strength, water resistance, toughness, and mildew resistance remains challenging. Herein, inspired by oysters, a multifunctional organic-inorganic hybrid soybean meal (SM)-based adhesive was fabricated by incorporating amino-modified carbon dots functionalized silica nanoparticles (CDs@SiO2) and dialdehyde chitosan (DCS) into SM matrix. DCS effectively enhanced the interface interactions of organic-inorganic phases and the rigid nanofillers CDs@SiO2 uniformly dispersed in the SM matrix, which provided energy dissipation to improve the adhesive's toughness. Owing to the stiff skeleton structure and enhanced crosslinking density, the crosslinker-modified SM (MSM)/DCS/CDs@SiO2-2 wood adhesive exhibited outstanding cold-pressing strength (0.74 MPa), wet shear strength (1.36 MPa), and long-term water resistance (49 d). Additionally, the resultant adhesive showed superior antimildew and antibacterial properties benefiting from the introduction of DCS. Intriguingly, the fluorescent properties endowed by carbon dots further broadened the application of adhesives for realizing security testing. This study opens a new pathway for the synthesis of multifunctional biomass adhesives in industrial and household applications.

The potential of self-activated carbon for adsorptive removal of toxic phenoxyacetic acid herbicide from water

Phenoxyacetic acid herbicides are widely used in agriculture for controlling weeds. These organic compounds are persistent and recalcitrant, often contaminating water and soil. Therefore, we studied five pristine biochars (BCs), and southern yellow pine (SYP) based self-activated carbon (SAC) for the adsorptive removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide. Among the tested adsorbents, SYP-SAC-15 demonstrated higher (>90%) 2,4-D removal from water. The SYP-SAC-15 was produced using a facile and green route where the biomass pyrolysis gases worked as activating agents creating a highly porous structure with a surface area of 1499.79 m2/g. Different adsorption kinetics and isotherm models were assessed for 2,4-D adsorption on SYP-SAC-15, where the data fitted best to pseudo-second order (R2 > 0.999) and Langmuir (R2 > 0.991) models, respectively. Consequently, the adsorption process was mainly dominated by the chemisorption mechanism with monolayer coverage of SYP-SAC-15 surface with 2,4-D molecules. At the optimum pH of 2, the maximum 2,4-D adsorption capacity of SYP-SAC-15 reached 471.70 mg/g. Furthermore, an increase in the water salinity demonstrated a positive influence on 2,4-D adsorption, whereas humic acid (HA) showed a negative impact on 2,4-D adsorption. The regeneration ability of SYP-SAC-15 showed excellent performance by retaining 71.09% adsorption capability at the seventh adsorption-desorption cycle. Based on the operating pH, surface area, spectroscopic data, kinetics, and isotherm modeling, the adsorption mechanism was speculated. The 2,4-D adsorption on SYP-SAC-15 was mainly governed by pore filling, electrostatic interactions, hydrogen bonding, hydrophobic and π-π interactions.

Bioinspired Synthesis of Silver Nanoparticles for the Remediation of Toxic Pollutants and Enhanced Antibacterial Activity

This research presents a novel and environmentally friendly approach for the synthesis of multifunctional nanobiocomposites for the efficient removal of toxic heavy metal and dye, as well as the disinfection of wastewater microorganisms. The nanobiocomposites (KAC-CS-AgNPs) were prepared by incorporating photochemically generated silver nanoparticles (AgNPs) within a chitosan (CS)-modified, high-surface-area activated carbon derived from kenaf (KAC), using a unique self-activation method. The even distribution of AgNPs was visible in the scanning electron microscopy images and a Fourier transform infra red study demonstrated major absorption peaks. The experimental results revealed that KA-CS-AgNPs exhibited exceptional adsorption efficiency for copper (Cu²⁺), lead (Pb²⁺), and Congo Red dye (CR), and showed potent antibacterial activity against Staphylococcus aureus and Escherichia coli. The maximum adsorption capacity (mg g^-1) of KAC-CS-AgNPs was 71.5 for Cu²⁺, 72.3 for Pb²⁺, and 75.9 for CR, and the adsorption phenomena followed on the Freundlich and Langmuir isotherm models and the second-order kinetic model (R² > 0.99). KAC-CS-AgNPs also exhibited excellent reusability of up to four consecutive cycles with minor losses in adsorption ability. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. The bacterial inactivation tests demonstrated that KAC-CS-AgNPs had a strong bactericidal effect on both E. coli and S. aureus, with MIC calculated for E. coli and S. aureus as 32 µg mL^-1 and 44 µg mL^-1, respectively. The synthesized bioinspired nanocomposite KAC-CS-AgNPs could be an innovative solution for effective and sustainable wastewater treatment and has great potential for commercial applications.

Achieving strong, stable, and durable underwater adhesives based on a simple and generic amino-acid-resembling design

Developing underwater adhesives is important in many applications. Despite extensive progress, achieving strong, stable, and durable underwater adhesion via a simple and effective way is still challenging, mainly due to the conflict between the interfacial and bulk properties. Here, we report a unique bio-inspired strategy to facilely construct superior underwater adhesives with desirable interfacial and bulk properties. For adhesive design, a hydrophilic backbone is utilized to quickly absorb water for effective dehydration, and a novel amino acid-resembling functional block is developed to provide versatile molecular interactions for high interfacial adhesion. Moreover, the conjunction of these two components enables the generation of abundant covalent crosslinks for robust bulk cohesion. Such a rational design allows the adhesive to present a boosted underwater adhesion (3.92 MPa to glass), remarkable durability (maintaining high strength after one month), and good stability in various harsh environments (pH, salt, high temperature, and organic solvents). This strategy is generic, allowing the derivation of more similar adhesive designs easily and triggering new thinking for designing bio-inspired adhesives and beyond.

Scalable Manufacturing of Environmentally Stable All-Solid-State Plant Protein-Based Supercapacitors with Optimal Balance of Capacitive Performance and Mechanically Robust

The development of advanced biomaterial with mechanically robust and high energy density is critical for flexible electronics, such as batteries and supercapacitors. Plant proteins are ideal candidates for making flexible electronics due to their renewable and eco-friendly natures. However, due to the weak intermolecular interactions and abundant hydrophilic groups of protein chains, the mechanical properties of protein-based materials, especially in bulk materials, are largely constrained, which hinders their performance in practical applications. Here, a green and scalable method is shown for the fabrication of advanced film biomaterials with high mechanical strength (36.3 MPa), toughness (21.25 MJ m^-3 ), and extraordinary fatigue-resistance (213 000 times) by incorporating tailor-made core-double-shell structured nanoparticles. Subsequently, the film biomaterials combine to construct an ordered, dense bulk material by stacking-up and hot-pressing techniques. Surprisingly, the solid-state supercapacitor based on compacted bulk material shows an ultrahigh energy density of 25.8 Wh kg^-1 , which is much higher than those previously reported advanced materials. Notably, the bulk material also demonstrates long-term cycling stability, which can be maintained under ambient condition or immersed in H₂ SO₄ electrolyte for more than 120 days. Thus, this research improves the competitiveness of protein-based materials for real-world applications such as flexible electronics and solid-state supercapacitors.

Guar gum, a low-cost sustainable biopolymer, for wastewater treatment: A review

Rapid population growth and the resultant pollution of freshwater resources have created a water stress condition reducing the availability of safe and affordable water. Guar gum, a biocompatible macromolecule obtained from the endosperm of the seeds of Cyamopsis tetragonolobus, is a fascinating raw material for multifunctional adsorbents. This review assembled the work conducted by various researchers over the past few decades and discussed the structure, properties, and different modifications methods employed to develop versatile guar gum-based adsorbent. The paper also summarized the recent progress of guar gum-based nanocomposites for the remediation of multiple hazardous substances such as organic dyes, toxic heavy metal ions, oil-water separation as well as inhibiting the growth of bacterial pathogens. Thus, the important contribution of guar gum composites to safeguard the water quality is highlighted which will overcome the limitations and streamline the future course of innovative research.

Lignocellulosic-Based Activated Carbon-Loaded Silver Nanoparticles and Chitosan for Efficient Removal of Cadmium and Optimization Using Response Surface Methodology

The cadmium-contaminated water body is a worldwide concern for the environment and toxic to human beings and the removal of cadmium ions from drinking and groundwater sustainably and cost-effectively is important. A novel nano-biocomposite was obtained by impregnating silver nanoparticles (AgNPs) within kenaf-based activated carbon (KAC) in the presence of chitosan matrix (CS) by a simple, facile photoirradiation method. The nano-biocomposite (CS-KAC-Ag) was characterized by an environmental scanning electron microscope equipped with energy dispersive X-ray spectroscopy (ESEM-EDX), Fourier-transform infrared spectroscopy (FTIR), and Brunauer−Emmett−Teller (BET) method. A Box−Behnken design of response surface methodology (RSM) was used to optimize the adsorption of Cd2+. It was found that 95.1% of Cd2+ (10 mg L−1) was eliminated at pH 9, contact time of 120 min, and adsorbent dosage of 20 mg, respectively. The adsorption of Cd2+ by CS-KAC-Ag is also in agreement with the pseudo-second-order kinetic model with an R2 (coefficient of determination) factor greater than 99%. The lab data were also corroborated by tests conducted using water samples collected from mining sites in Mexico. Along with Cd2+, the CS-KAC-Ag exhibited superior removal efficiency towards Cr6+ (91.7%) > Ni2+ (84.4%) > Co2+ (80.5%) at pH 6.5 and 0.2 g L−1 dose of the nano-adsorbent. Moreover, the adsorbent was regenerated, and the adsorption capacity remained unaltered after five successive cycles. The results showed that synthesized CS-KAC-Ag was a biocompatible and versatile porous filtering material for the decontamination of different toxic metal ions.

Biomimetic lignin-protein adhesive with dynamic covalent/hydrogen hybrid networks enables high bonding performance and wood-based panel recycling

Exploring the reusability of wood-based panels is imperative in the wood industry for sustainable development and carbon balance. Non-reusable adhesives make wood-based panel recycling difficult. In this study, inspired by the adhesion and de-adhesion behavior of snail slime, we built dynamic covalent/hydrogen hybrid networks into adhesive system for achieving both high bonding performance and reusability. Specifically, the softwood lignin was purified and pretreated by ultrasonication to form a catechol structure (UAL) and then combined with soybean protein to develop a 100 % bio-based wood adhesive. The catechol structure of UAL formed dynamic covalent bonds (CN) with the amino groups of the protein to improve the water resistance and formed multiple hydrogen bonds as a sacrificial network to improve the toughness of the adhesive. Thus, the wet shear strength of plywood bonded by the resultant adhesive improved by 101.4 % to 1.37 MPa. The adhesive also exhibited flame retardancy (LOI = 37.7 %), mildew resistance (60 h), and antibacterial performance (inhibition zone = 8 mm). Notably, owing to the rearrangement of dynamic covalent/hydrogen hybrid networks and the thermoplastic property of UAL, the resultant adhesive was reusable (3 cycles) and degradable (2 months), which provides a potential method for the reuse of wood-based panels.

Preparation of a high bonding performance soybean protein-based adhesive with low crosslinker addition via microwave chemistry

Human health and environmental protection demand wood-based panel industry for innovative soy-based adhesives with high production efficiency, straightforward synthesis processes, non-toxicity, and high bonding performance. A simple and efficient microwave pretreatment process and low addition of bio-derived crosslinking agent was used in this study to prepare a non-toxic and high-bonding performance soybean protein-based adhesive. After 4 min of microwave pretreatment time, the complex quaternary structure of soybean protein molecule unfolds, the soybean protein disperses evenly and stably, and active groups of soybean protein molecules are exposed. After adding 3.85% crosslinking agent, the moisture absorption rate of the soybean protein-based adhesive decreases by 41.77%, the residual rate increases by 3.68%, and the wet shear strength of the resultant plywood increases to 1.12 MPa, which satisfies requirement of interior use plywood. Compared with previously reported soy-based adhesives, this adhesive is dependent on fewer chemical reagents, but has good bonding performance. The 204.41% of relative cell viability indicates the resultant adhesive was non-toxic. The proposed high-efficiency, high-performance, non-toxic biomass adhesive has great prospects for the industrial application.

Mesoporous activated carbon as a green adsorbent for the removal of heavy metals and Congo red: Characterization, adsorption kinetics, and isotherm studies

In this study, an effective and green adsorbent was prepared by the self- activation of kenaf fiber and then the kenaf-based activated carbon (KAC) was applied for the removal of lead Pb(II), copper Cu(II), and Congo red (CR) dye from an aqueous solution by the process of adsorption. The surface morphology of mesoporous adsorbent was characterized. The KAC showed good capacity of adsorption of as Pb(II), Cu(II), and anionic dye CR in very short period of agitation. The adsorbent efficiency of metal ions and dye was estimated by varying the adsorbent dose, pH, contact time, initial metals and dye concentration, and temperature. Optimum adsorption of metal ions and CR dye was observed at pH 6, and at pH 4 at 120 min, respectively. The adsorption isotherm was described by the Langmuir and Freundlich isotherm equations. The green adsorbent followed the pseudo-second-order kinetic model with correlation coefficients R² value >0.99. The increase in adsorption temperature enhanced the adsorption efficiency for both heavy metals and dye. The KAC showed no significant loss of the adsorption capacity after 3 cycles of reuse.

Lightweight, strong, moldable wood via cell wall engineering as a sustainable structural material

[Figure: see text].

"Green" Flexible Electronics: Biodegradable and Mechanically Strong Soy Protein-Based Nanocomposite Films for Human Motion Monitoring

Soy protein isolate (SPI) is envisioned as a promising alternative to fabricate "green" flexible electronics, showing great potential in the field of flexible wearable electronics. However, it is challenging to simultaneously achieve conductive film-based human motion-monitoring strain sensors with reliable fatigue resistance, robust mechanical property, environmental degradability, and sensing capability of human motions. Herein, we prepared a series of SPI-based nanocomposite films by embedding a surface-hydroxylated high-dielectric constant inorganic filler, BaTiO3, (HBT) as interspersed nanoparticles into a biodegradable SPI substrate. In particular, the fabricated film comprising 0.5 wt % HBT and glycerin (GL), namely, SPI-HBT0.5-GL0.5, presents multifunctional properties, including a combination of excellent toughness, tensile strength, conductivity, translucence, recyclability, and excellent thermal stability. Meanwhile, this multifunctional film could be simply degraded in phosphate buffered saline solution and does not cause any pollution to the environment. Attractively, wearable sensors prepared with this particular material (SPI-HBT0.5-GL0.5) displayed excellent biocompatibility, prevented the occurrence of an immune response, and could accurately monitor various types of human joint motions and successfully remain operable after 10,000 cycles. These properties make the developed SPI-based film a great candidate in formulating biobased and multifunctional wearable electronics.

Nacre-Inspired Strong and Multifunctional Soy Protein-Based Nanocomposite Materials for Easy Heat-Dissipative Mobile Phone Shell

Inspired by the hierarchically ordered "brick and mortar" (BM) architecture of natural nacre, in this study a rational assembly of boron nitride (BN) nanosheets was introduced into a mixture of trimethylolpropane triglycidyl ether (TTE) and soy protein isolate (SPI), and a strong and multifunctional SPI-based nanocomposite film with multinetwork structure was synthesized. At a low BN loading (<0.5%), the resulting multifunctional film was flexible, antiultraviolet, and nearly transparent and also displayed good thermal diffusion ability and exhibited an excellent combination of high tensile strength (36.4 MPa) and thermal conductivity (TC, 2.40 W·m^-1·K^-1), surpassing the performances of various types of petroleum-based plastics (displayed a tensile strength ranging from 1.9 to 21 MPa and TC ranging from 0.55-2.13 W·m^-1·K^-1), including nine different types of materials currently utilized for mobile phone shells, suggesting its vast potential in practical applications.

Sandcastle worm-inspired phytic acid and magnesium oxychloride cement copolymerization for performance enhancement

The development of magnesium oxychloride cement (MOC) can convert wastes in the potash industry into valuable products and reduce CO₂ emission. The use of acid radicals has the potential to enhance the water resistance of MOC. However, because of the internal stress formed during the crystallization process, the occurrence of cracks accompanied by a significant decrease in the mechanical properties is inevitable. Inspired by the sandcastle worm and organic-inorganic copolymerization, a novel strategy was proposed, which employed phytic acid (PA) to copolymerize with phase 5 crystals to reduce the internal stress and prevent crack generation. XPS and TG-DSC analyses revealed that organic-inorganic copolymers were successfully produced. Furthermore, the compressive strength (CS) and water resistance of MOC-PA were significantly enhanced. The enhanced properties were associated with the coordination bonds and high tension of the rigid rings in phytic acid, which was sufficient to overcome the internal stress. Additionally, the repeated hydrolysis of rod-like phase 5 generated a gel-like phase from the outside inward, enhancing their water resistance. Compared with MOC-0, MOC-0.6 showed a 17.8% increase in CS and a 102.3% increase in water resistance. The microscopic mechanisms of the enhanced CS and water resistance of high-performance greener cements were proposed.

Optically Transparent Bamboo with High Strength and Low Thermal Conductivity

The objective of this study is to convert bamboo into a transparent material with great optical transmittance and good strength. Bamboo has a much faster regeneration rate than wood, but its high density and high extractive content make it challenging to produce transparent products. This study presents a simple and effective approach that could address this challenge. Pretreatment of bamboo with low concentration sodium hydroxide greatly improved the preparation efficiency of transparent bamboo. The transparent bamboo with a thickness of 1 mm and cellulose volume fraction of 22% made from the pretreated bamboo exhibited an improved total optical transmissivity up to 80%, which was 60% higher than that of untreated bamboo. Compared to transparent wood (TW), although the transmissivity of transparent bamboo was slightly lower, its mechanical strength was almost doubled. Besides, the developed transparent bamboo exhibited a low heat conductivity of 0.203 W m^-1 K^-1, being about 10% lower than that of TW (0.225 W m^-1 K^-1) and approximately 80% lower than that of common glass material (0.974 W m^-1 K^-1). The transparent bamboo would significantly enhance energy-saving performance, being a promising alternative to traditional glass.

Phytic acid-assisted fabrication for soybean meal/nanofiber composite adhesive via bioinspired chelation reinforcement strategy

Adhesives are commonly used in the wood industry, such as plywood, fiberboard, and particleboard, for making furniture, flooring, kitchen cabinets, and wall materials. However, almost all of these adhesives come from petroleum resources and release toxic substances that pollute the environment and endanger human health. Therefore, it is necessary to promote the production of eco-friendly adhesives. The development of plant-protein-based adhesives can increase the value of agricultural wastes and reduce the environmental hazards. However, their industrial application is limited by their poor mechanical strength and inferior water resistance. The main purpose of this study was to prepare a green effective reinforcer to improve the water resistance and mechanical strength of soybean meal (SM) adhesive. To achieve the above goals, a natural chelating agent phytic acid (PA)-mediated aminoclay-cellulose nanofiber (AC@CNF) nanohybrid was prepared. Then, the AC@CNF-PA nanohybrids were combined with SM to prepare a high-performance SM-based adhesive. The water resistance of the modified adhesive was remarkably improved, with 105.2 % higher than that of the unmodified SM adhesive in wet shear strength. Moreover, the modified adhesive showed good cytocompatibility, biodegradability, and flame retardancy. This work suggested a new approach in preparing green high-performance protein-based adhesives.

Novel 2D Dynamic Elasticity Maps for Inspection of Anisotropic Properties in Fused Deposition Modeling Objects

In this study, a novel ultrasonic non-destructive and non-invasive elastography method was introduced and demonstrated to evaluate the mechanical properties of fused deposition modeling 3D printed objects using two-dimensional dynamical elasticity mapping. Based on the recently investigated dynamic bulk modulus and effective density imaging technique, an angle-dependent dynamic shear modulus measurement was performed to extract the dynamic Young’s modulus distribution of the FDM structures. The elastographic image analysis demonstrated the presence of anisotropic dynamic shear modulus and dynamic Young’s modulus existing in the fused deposition modeling 3D printed objects. The non-destructive method also differentiated samples with high contrast property zones from that of low contrast property regions. The angle-dependent elasticity contrast behavior from the ultrasonic method was compared with conventional and static tensile tests characterization. A good correlation between the nondestructive technique and the tensile test measurements was observed.

Effect of lignin on the self-bonding of a natural fiber material in a hydrothermal environment: Lignin structure and characterization

Self-bonding natural fiber materials (SNFMs) were prepared at different initial moisture contents (IMCs) through a molding pressing process. The self-bonding mechanism of the SNFMs was deduced from the chemical and structural changes of lignin and their mechanical strengths. The structural transformations of milled wood lignin (MWL) in the SNFMs were investigated by two-dimensional heteronuclear single quantum coherence, quantitative 31P-nuclear magnetic resonance spectra, gelpermeation chromatography, and thermogravimetric analysis. As IMC increased from 0% to 80%, the tensile strength increased from 23.0 to 70.0 MPa and the density increased from 0.99 to 1.05 g/cm3. IMC affected the distribution and abundance of the typical lignin linkages (β-O-4', β-β, and β-5') and the S-OH/G-OH ratios of lignin. Moreover, as IMC increased, the aliphatic hydroxyl groups proportionally decreased, while the condensed phenolic and non-condensed phenolic hydroxyl groups increased, the molecular weight of MWL became larger, and the thermal stability of lignin improved. These findings indicate the simultaneous occurrence of depolymerization and condensation reactions of lignin. The condensation reaction dominated, improving the mechanical strength of the material. Our results explain (at least partly) the self-bonding mechanism of SNFMs.

A Tough and Mildew-Proof Soybean-Based Adhesive Inspired by Mussel and Algae

Despite the recent advances in protein-based adhesives, achieving strong adhesion and mold resistance in wet environment is challenging. Herein, a facile fabrication technology of preparing tough bio-adhesive by incorporating soybean meal and blood meal is presented. Inspired by the marine mussel byssi and brown algae, metal coordination was introduced into a loosely bound protein system to construct multiple chemical cross-linking networks. Mixed alkali-modified blood meal (mBM) was mixed with soybean meal, then 1,6-hexane dioldiglycidyl ether (HDE) and zinc ion were introduced to fabricate soybean meal and blood meal-based adhesives. The attained adhesives exhibited good thermal stability, water resistance (the wet shear strength is 1.1 MPa), and mold resistance, with appropriate solid content (34.3%) and relatively low moisture uptake (11.9%). These outstanding performances would be attributed to the reaction of 1,6-hexane dioldiglycidyl ether with protein to form a preliminary cross-linking network; subsequently, the coordination of zinc ions with amino or carboxyl strengthened and toughened the adhesive. Finally, the calcium ions gelled the adhesives, providing cohesion force and making the network structure more compact. This study realized the value-added utilization of protein co-products and developed a new eco-friendly bio-based adhesive.

Soybean Meal-Based Wood Adhesive Enhanced by Phenol Hydroxymethylated Tannin Oligomer for Exterior Use

Bio-based adhesives have low water resistance and they are less durable than synthetic adhesives, which limits their exterior applications. In this study, a bio adhesive was developed from soybean meal and larch tannin that was designed for exterior use. Phenol hydroxymethylated tannin oligomer (PHTO) was synthesized and then mixed with soybean meal flour in order to obtain a soybean meal-based adhesive (SPA). The results showed that the moisture absorption rate, residual rate, and solid content of SPA with 10 wt % PHTO (mass ratio with respect to the entire adhesive) were improved by 22.8%, 11.6%, and 6.8%, respectively, as compared with that of pure SPA. The wet shear strength of plywood with SPA with 10 wt % PHTO (boiling in 100 °C water for 3 h) was 1.04 MPa when compared with 0 MPa of pure SPA. This met the bond strength requirement of exterior-use plywood (GB/T 9846.3-2004). This improved adhesive performance was mainly due to the formation of a crosslinked structure between the PHTO and the protein and also PHTO self-crosslinking. The formaldehyde emission of the resulting plywood was the same as that of solid wood. The PHTO-modified SPA can potentially extend the applications of SPAs from interior to exterior plywood.

A One-Pot Synthesis and Characterization of Antibacterial Silver Nanoparticle-Cellulose Film

Using N,N-dimethylacetamide (DMAc) as a reducing agent in the presence of PVP-K30, the stable silver nanoparticles (Ag-NPs) solution was prepared by a convenient method for the in situ reduction of silver nitrate. The cellulose-Ag-NPs composite film (CANF) was cast in the same container using lithium chloride (LiCl) giving the Ag-NPs-PVP/DMAc solution cellulose solubility as well as γ-mercaptopropyltrimethoxysilane (MPTS) to couple Ag-NPs and cellulose. The results showed that the Ag-NPs were uniformly dispersed in solution, and the solution had strong antibacterial activities. It was found that the one-pot synthesis allowed the growth of and cross-linking with cellulose processes of Ag-NPs conducted simultaneously. Approximately 61% of Ag-NPs was successfully loaded in CANF, and Ag-NPs were uniformly dispersed in the surface and internal of the composite film. The composite film exhibited good tensile properties (tensile strength could reach up to 86.4 MPa), transparency (light transmittance exceeds 70%), thermal stability, and remarkable antibacterial activities. The sterilization effect of CANF0.04 against Staphylococcus aureus and Escherichia coli exceed 99.9%. Due to low residual LiCl/DMAc and low diffusion of Ag-NPs, the composite film may have potential for applications in food packaging and bacterial barrier.

Bioinspired and biomineralized magnesium oxychloride cement with enhanced compressive strength and water resistance

High CO₂ emissions during the production process of ordinary Portland cement (OPC) promoted greener-cement development, wherein the application of magnesium oxychloride cement (MOC) can add value to waste in potash industry and reduce environmental hazards. However, its application was restricted by its inferior water resistance. It's a challenge to remarkably increase both the compressive strength and water resistance of MOC. Herein, we demonstrate that cornstarch/sodium polyacrylate (PAAS) MOC composites exhibit increased compressive strength and water resistance. Moreover, the biomineralization process encourages the growth and alignment of phase 5 crystals by a cornstarch template with hydroxyl groups, thus enhancing the compressive strength of MOC. The chelation of magnesium ions and the transformation of phase 5 crystal structure by PAAS can significantly enhance the water resistance of MOC. This composite exhibits a 21.0% increase in compressive strength, and the softening coefficient is also increased from 0.48 to 0.81 in comparison with unmodified-MOC. Meanwhile, the hydrogen bonds between cornstarch and elemental Cl obviously decrease the efflorescence phenomena of the MOC. This MOC composite with a markedly increased compressive strength and water resistance, which was prepared by a facile and green method, may have potential applications in building development and the replacement of OPC.

A Bio-Hygromorph Fabricated with Fish Swim Bladder Hydrogel and Wood Flour-Filled Polylactic Acid Scaffold by 3D Printing

Non-powered adaptive systems are attractive in the construction of environment actuators, meteorosensitive architectures, biomedical devices, and soft robotics. Combining hydrophilic materials and anisotropic structures to mimic self-morphing plant structures has been demonstrated as an effective approach to creating artificial hygromorphs. The convenience of 3D printing technologies in shaping programmable complex structures facilitates the imitation of complex anisotropic plant structures. In this research, we constructed a bio-hygromorph using fish swim bladder hydrogel as the hydrophilic material and wood flour-filled polylactic acid (WPLA) scaffold, which was printed with fused deposition modeling (FDM) 3D printing technology (3DP). The environmental benign bio-hygromorph displayed morphing abilities triggered by moisture content changes, as the fish swim bladder hydrogel swelled and shrunk during absorption and desorption cycles. The strain disproportion of the two-layered composite structure in the bio-hygromorph drove the bending deformation. Stress analyses performed with finite element analysis (FEA) also revealed the mechanism behind the moisture content driven morphing of the bio-hygromorph. Notably, the bio-hygromorph exhibited faster response times to moisture absorption than desorption, which may donate actuators' different attributes in distinct moisture conditions.

A Tough, Water-Resistant, High Bond Strength Adhesive Derived from Soybean Meal and Flexible Hyper-Branched Aminated Starch

Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving crosslinking density is generally accompanied by a toughness reduction of the adhesive. Herein, we developed a flexible long-chain starch with a hyper-branched structure (HD), and incorporated it with SM and a crosslinking agent to prepare a novel SM adhesive. Results showed that this adhesive exhibited both excellent water resistance and enhanced toughness. The wet bond strength of plywood fabricated using this adhesive was 354.5% higher than that of SM adhesive. These achievements are because introducing HD with hyper-branched groups enhanced crosslinking density, while HD's flexible long-chain structure improved toughness of the adhesive. This HD can promote the development of tough and hydrophobic bio-based composites.

Integrated network analysis to identify the key genes, transcription factors, and microRNAs involved in hepatocellular carcinoma

HCC (hepatocellular carcinoma), which can be induced by cirrhosis and viral hepatitis infection, is the most frequent form of liver cancer. This study is performed to investigate the mechanisms of HCC. GSE57957 was obtained from Gene Expression Omnibus database, including 39 HCC samples and 39 adjacent non-tumorous samples. The DEGs (differentially expressed genes) were screened using the limma package in R, and then were conducted with enrichment analysis using "BioCloud" platform. Using STRING database, WebGestalt tool, as well as ITFP and TRANSFAC databases, PPI (protein-protein interaction) pairs, miRNA (microRNA)-target pairs, and TF (transcription factor)-target pairs separately were predicted. Followed by integrated network was constructed by Cytoscape software and module analysis was performed using the MCODE plugin of Cytoscape software. There were 518 DEGs identified from the HCC samples, among which 17 up-regulated genes (including MCM2, MCM6, and CDC20) and 5 down-regulated genes could also function as TFs. In the integrated network for the down-regulated genes, FOS and ESR1 had higher degrees, and both of them were targeted by miR-221 and miR-222. Additionally, MCM2 had interaction with MCM6 in the up-regulated module with the highest score. MCM2, MCM6, CDC20, FOS, ESR1, miR-221 and miR-222 might affect the pathogenesis of HCC.

Facile Fabrication of Self-Healable and Antibacterial Soy Protein-Based Films with High Mechanical Strength

Soy protein isolate (SPI), a ubiquitous and readily available biopolymer, has drawn increasing attention because of its sustainability, abundance, and low price. However, the poor mechanical properties, tedious performance adjustments, irreversible damage, and weak microorganism resistance have limited its applications. In this study, a facile but delicate strategy is proposed to fabricate an excellently self-healable and remarkably antibacterial SPI-based material with high mechanical strength by integrating polyethyleneimine (PEI) and metal ions (Cu(II) or Zn(II)). The tensile strengths of the SPI/PEI-Cu-0.750 and SPI/PEI-Zn-0.750 films reach up to 10.46 ± 0.50 and 9.06 ± 0.62 MPa, which is 367.06 and 306.28% strength increase compared to that of neat SPI film, respectively. Due to abundant non-covalent bonds and low glass transition temperature of the network, both SPI/PEI-Cu and SPI/PEI-Zn films exhibit a satisfactory self-healing behavior even at room temperature. Furthermore, SPI/PEI-Cu and SPI/PEI-Zn films demonstrate high bacterial resistance against Escherichia coli and Staphylococcus aureus. This facile strategy of establishing dynamic networks in a biomaterial with numerous excellent properties will enormously expand the scope of its applications, especially in the field of recyclable and durable materials.

Large-Size Transparent Wood for Energy-Saving Building Applications

As an energy-saving building material, transparent wood (TW) is highly attractive because of the advantages of high optical transmittance, excellent mechanical properties, and good thermal insulation. However, the current research is limited to fabricating small-size samples in the laboratory because thick or large-size transparent wood is almost impossible to be achieved. A method that can easily and efficiently produce transparent wood with any size and any thickness is desirable for practical applications. Transparent wood made from wood fibers as a substrate allows the cell walls to bind more tightly to the impregnated polymer, resulting in high light transmittance. Compared with wood prepared by using previously reported approaches, the transparent wood prepared by this new method not only retains the same advantages but also has higher preparation efficiency and is suitable for large-scale production. Under a simulated real environment, the retainability of indoor temperature by a sample house utilizing the transparent wood reveals excellent thermal insulation of the fiber-based transparent wood owing to its low thermal conductivity, showing significant benefits in saving thermal energy.

Effect of thermal treatment with water, H2SO4 and NaOH aqueous solution on color, cell wall and chemical structure of poplar wood

Thermal treatments with water, diluted acid, and diluted alkali aqueous solution of poplar wood blocks were carried out in a Teflon-lined autoclave at three temperatures. The effects of different liquids and temperatures on wood surface color, cell wall microstructure, and chemical structures were investigated by the chromameter, scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). From the chromameter, it was observed that the lightness value decreased with temperature for all treatment conditions. The a* value increased with temperature in all liquid treatments. The b* value increased with temperature in hydrothermal and thermal with H₂SO₄ treatment but decreased with temperature in thermal with NaOH treatment. The total color difference (ΔE) was slightly changed in the hydrothermal treatment, but dramatically changed in the thermal with H₂SO₄ and NaOH aqueous treatments. SEM showed that the cell wall structure was damaged differently with different reagents and temperature. Middle lamella layers were always fractured in hydrothermal and NaOH treatments. However, both middle lamella and secondary cell wall were damaged after the H₂SO₄ treatment and intensified with temperature. These fractures usually parallel with the S2 layer microfibril angle (MFA) in the fiber cell wall. The FTIR analysis suggested that the chemical structure was obviously changed after the thermal with H₂SO₄ and NaOH treatments. And the missing or decreasing C=O absorption peak indicated hemicellulose is degraded and new compounds produced during thermal with H₂SO₄ and NaOH treatment. On the other hand, lignin was partly degraded in the H₂SO₄ treatment and guaiacyl nuclei was degraded before syringyl nuclei.

Sodium Hydroxide-Free Soy Protein Isolate-Based Films Crosslinked by Pentaerythritol Glycidyl Ether

The soy protein isolate (SPI), sodium dodecylbenzenesulfonate (SDBS) and pentaerythritol glycidyl ether (PEGE) were used to make biodegradable films in this study. Unlike the usual method that adding sodium hydroxide (NaOH) during the SPI-based film casting, SDBS was used as a surfactant playing the similar role as NaOH. Since NaOH is a chemical with corrosiveness and toxicity, the replacing of NaOH by SDBS might reduce the hazard threat during the utilization of SPI-based films in food packing application. Furthermore, the presentation of SDBS helped dispersing the hydrophobic PEGE into the hydrophilic SPI. PEGE is a crosslinking agent with multiple reactive epoxy groups. The chemical structures and micro morphologies of the fabricated films were investigated by means of FTIR, XRD, and SEM. The thermal stabilities of the films were examined by means of the thermo-gravimetric analysis. After the chemical crosslinking, the ultimate tensile strength of the film was significantly increased, meanwhile, the water absorption was dramatically decreased. It was concluded that the SPI-based film containing 4% PEGE achieved the optimal performance.

Effect of light-delignification on mechanical, hydrophobic, and thermal properties of high-strength molded fiber materials

This study developed a high-strength molded fiber material (HMFM) using pulp fibers, which could be a good substitute for plastic and solid wood materials. The surface composition, microstructure and thermal properties of HMFM were investigated by XPS, SEM and DSC, respectively. The SEM observations showed that the obvious adhesive substances and agglomeration appeared among fibers, and the inter-fiber contact area and binding tightness increased after the light-delignification. The XPS examination showed that the oxygen-rich composition on the outer surface of HMFM were reduced, and the outer surface coverage of lignin increased from 70.05% to 90.15% after the light-delignification. The DSC observation showed that the thermal stability of HMFM decreased, the temperature for the maximum rate of mass loss decreased from 370 °C to 345.6 °C, and the enthalpy value required for decomposition was reduced from 110.8 J/g to 68.0 J/g after the light-delignification. The mechanical and hydrophobic properties of HMFM were obviously improved after the light-delignification. When the content of lignin decreased from 24.9% to 11.45%, the density of HMFM increased by 6.0%, the tensile strength increased by 22.0%, the bending strength increased by 23.9%, and the water contact angle increased from 64.3°-72.7° to 80.8°-84.3°.

Adding nickel formate in alkali lignin to increase contents of alkylphenols and aromatics during fast pyrolysis

The composition of pyrolysis vapors obtained from alkali lignin pyrolysis with the additive of nickel formate was examined using the pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). Characterization of bio-chars was performed using X-ray diffraction (XRD). Results showed that the nickel formate significantly increased liquid yield, simplified the types of alkali lignin pyrolysis products and increased individual component contents. The additive of nickel formate increased contents of alkylphenols and aromatics from alkali lignin pyrolysis. With an increase in temperature, a greater amount of the relative contents can be achieved. The nickel formate was thermally decomposed to form hydrogen, resulting in hydrodeoxygenation of alkali lignin during pyrolysis. It was also found that Ni is in favor of producing alkylphenols. The analysis based on the experimental result provided evidences used to propose reaction mechanism for pyrolysis of nickel formate-assisted alkali lignin.

Fabrication of Wood-Rubber Composites Using Rubber Compound as a Bonding Agent Instead of Adhesives

Differing from the hot-pressing method in the manufacturing of traditional wood-rubber composites (WRCs), this study was aimed at fabricating WRCs using rubber processing to improve water resistance and mechanical properties. Three steps were used to make WRCs, namely, fiber-rubber mixing, tabletting, and the vulcanization molding process. Ninety-six WRC panels were made with wood fiber contents of 0%-50% at rotor rotational speeds of 15-45 rpm and filled coefficients of 0.55-0.75. Four regression equations, i.e., the tensile strength (Ts), elongation at break (Eb), hardness (Ha) and rebound resilience (Rr) as functions of fiber contents, rotational speed and filled coefficient, were derived and a nonlinear programming model were developed to obtain the optimum composite properties. Although the Ts, Eb and Rr of the panels were reduced, Ha was considerably increased by 17%-58% because of the wood fiber addition. Scanning electron microscope images indicated that fibers were well embedded in rubber matrix. The 24 h water absorption was only 1%-3%, which was much lower than commercial wood-based composites.

Tensile strains give rise to strong size effects for thermal conductivities of silicene, germanene and stanene

Based on first principles calculations and self-consistent solution of the linearized Boltzmann-Peierls equation for phonon transport approach within a three-phonon scattering framework, we characterize lattice thermal conductivities k of freestanding silicene, germanene and stanene under different isotropic tensile strains and temperatures. We find a strong size dependence of k for silicene with tensile strain, i.e., divergent k with increasing system size; however, the intrinsic room temperature k for unstrained silicene converges with system size to 19.34 W m(-1) K(-1) at 178 nm. The room temperature k of strained silicene becomes as large as that of bulk silicon at 84 μm, indicating the possibility of using strain in silicene to manipulate k for thermal management. The relative contribution to the intrinsic k from out-of-plane acoustic modes is largest for unstrained silicene, ∼39% at room temperature. The single mode relaxation time approximation, which works reasonably well for bulk silicon, fails to appropriately describe phonon thermal transport in silicene, germanene and stanene within the temperature range considered. For large samples of silicene, k increases with tensile strain, peaks at ∼7% strain and then decreases with further strain. In germanene and stanene, increasing strain hardens and stabilizes long wavelength out-of-plane acoustic phonons, and leads to similar k behaviors to those of silicene. These findings further our understanding of phonon dynamics in group-IV buckled monolayers and may guide transfer and fabrication techniques for these freestanding samples and engineering of k by size and strain for applications of thermal management and thermoelectricity.

Property enhancement of soy protein isolate-based films by introducing POSS

To enhance the mechanical and water-resistant properties of soy protein isolate (SPI) based films, hydrophobic TriSilanolPhenyl polyhedral oligomeric silsesquioxanes (POSS) was incorporated to modify the SPI films. POSS has three SiOH groups in a molecular, which is employed to cross-link SPI with the help of 3-glycidoxypropyltrimethoxysilane (GPTMS). POSS is a structure of eight phenol groups, playing a critical role in improving the physical and mechanical properties. The X-ray diffraction (XRD) and attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FT-IR) were used to characterize the films. The degree of reaction of SiOH groups in the POSS was estimated to be 53.0% according with the absorbance of ATR FT-IR spectra. Although the elongation at break was reduced by 52.6%, the tensile modulus, tensile strength and 10% offset yield strength were significantly increased by 86.6%, 34.0% and 56.8%, respectively, due to the cross-linking reactions among SPI, GPTMS and POSS. The results of water-resistant tests showed that the 24-hour water absorption was dramatically reduced by 54.7%.

Soy protein isolate-based films cross-linked by epoxidized soybean oil

Property enhancement of soy protein isolate-based film was achieved by introducing an environmentally friendly cross-linking agent, epoxidized soybean oil.

Enhancement of mechanical and thermal properties of Poplar through the treatment of glyoxal-urea/nano-SiO2

An environmental-friendly glyoxal-urea (GU) resin is synthesized from urea and glyoxal, and combined with nano-SiO₂ to treat Poplar wood and endow it superior mechanical and thermal properties.

Quality improvement of pyrolysis oil from waste rubber by adding sawdust

This work was aimed at improving the pyrolysis oil quality of waste rubber by adding larch sawdust. Using a 1 kg/h stainless pyrolysis reactor, the contents of sawdust in rubber were gradually increased from 0%, 50%, 100% and 200% (wt%) during the pyrolysis process. Using a thermo-gravimetric (TG) analyzer coupled with Fourier transform infrared (FTIR) analysis of evolving products (TG-FTIR), the weight loss characteristics of the heat under different mixtures of sawdust/rubber were observed. Using the pyrolysis-gas chromatography (GC)-mass spectrometry (Py-GC/MS), the vapors from the pyrolysis processes were collected and the compositions of the vapors were examined. During the pyrolysis process, the recovery of the pyrolysis gas and its composition were measured in-situ at a reaction temperature of 450 °C and a retaining time of 1.2s. The results indicated that the efficiency of pyrolysis was increased and the residual carbon was reduced as the percentage of sawdust increased. The adding of sawdust significantly improved the pyrolysis oil quality by reducing the polycyclic aromatic hydrocarbons (PAHs) and nitrogen and sulfur compounds contents, resulting in an improvement in the combustion efficiency of the pyrolysis oil.

Pressure prediction model for compression garment design

Based on the application of Laplace's law to compression garments, an equation for predicting garment pressure, incorporating the body circumference, the cross-sectional area of fabric, applied strain (as a function of reduction factor), and its corresponding Young's modulus, is developed. Design procedures are presented to predict garment pressure using the aforementioned parameters for clinical applications. Compression garments have been widely used in treating burning scars. Fabricating a compression garment with a required pressure is important in the healing process. A systematic and scientific design method can enable the occupational therapist and compression garments' manufacturer to custom-make a compression garment with a specific pressure. The objectives of this study are 1) to develop a pressure prediction model incorporating different design factors to estimate the pressure exerted by the compression garments before fabrication; and 2) to propose more design procedures in clinical applications. Three kinds of fabrics cut at different bias angles were tested under uniaxial tension, as were samples made in a double-layered structure. Sets of nonlinear force-extension data were obtained for calculating the predicted pressure. Using the value at 0° bias angle as reference, the Young's modulus can vary by as much as 29% for fabric type P11117, 43% for fabric type PN2170, and even 360% for fabric type AP85120 at a reduction factor of 20%. When comparing the predicted pressure calculated from the single-layered and double-layered fabrics, the double-layered construction provides a larger range of target pressure at a particular strain. The anisotropic and nonlinear behaviors of the fabrics have thus been determined. Compression garments can be methodically designed by the proposed analytical pressure prediction model.

The effect of intertube van der Waals interaction on the stability of pristine and functionalized carbon nanotubes under compression

This paper investigates the effect of intertube van der Waals interaction on the stability of pristine and covalently functionalized carbon nanotubes under axial compression, using molecular mechanics simulations. After regulating the number of inner layers of the armchair four-walled (5, 5)@(10, 10)@(15, 15)@(20, 20) and zigzag four-walled (6, 0)@(15, 0)@(24, 0)@(33, 0) carbon nanotubes, the critical buckling strains of the corresponding tubes are calculated. The results show that each of the three inner layers in the functionalized armchair nanotube noticeably contributes to the stability of the outermost tube, and together increase the critical strain amplitude by 155%. However, the three inner layers in the corresponding pristine nanotube, taken together, increase the critical strain of the outermost tube by only 23%. In addition, for both the pristine and functionalized zigzag nanotubes, only the (24, 0) layer, among the three inner layers, contributes to the critical strain of the corresponding outermost tube, by 11% and 29%, respectively. The underlying mechanism of the enhanced stability related to nanotube chirality and functionalization is analyzed in detail.

Surface reconstructions and stability of X-shaped carbon nanotube junction

A complete surface reconstruction takes place after a local connection between two crossed tubes is established, leading to the creation of an extended X-shaped junction constituted by topological defects with smooth negative curvature. Molecular-dynamics simulations show that the surface reconstructions occur through (1) generalized Stone-Wales transformation and (2) the movement of sp and sp3 atoms and their transformation to sp2 atoms by bond rearrangement. Based on both the principle of energy minimization and a generalized Euler's rule, it is demonstrated that the most stable structure for X junctions contains only 12 heptagons. The annealing temperature influences the topological structure and stability of junctions.

Changes in light-induced fluorescence of cervical collagen in guinea pigs during gestation and after sodium nitroprusside treatment

Light-induced fluorescence (LIF) of collagen was used to investigate in vivo changes in cervical collagen in guinea pigs during gestation and following sodium nitroprusside treatment. Natural fluorescence of collagen is due to collagen cross-linking molecules that connect single collagen fibers and therefore provide rigidity of the cervical stroma. LIF of cervical collagen was measured from the surface of the exocervix in anesthetized nonpregnant and timed pregnant guinea pigs at different times of gestation with an instrument designed in our lab (Collascope). Measurements were also performed in guinea pigs at midgestation before and 8 hours after intracervical treatment with sodium nitroprusside. Collagen fluorescence decreased significantly as pregnancy progressed, reached lowest values at delivery, and increased gradually postpartum. Treatment with sodium nitroprusside, but not with the vehicle, caused a significant decrease in LIF (p = 0.007). We conclude, that LIF changes in the cervix reflect the gradual cervical softening (ripening) during pregnancy and the return to the rigid state of the cervix postpartum. Cervical softening during pregnancy, and after sodium nitroprusside treatment, is associated with a decrease in collagen cross-links. Measurements of LIF can be used to investigate cervical softening in vivo.