A tough bio-adhesive inspired by pearl layer and arthropod cuticle structure with desirable water resistance, flame-retardancy, and antibacterial property

Soy Protein Adhesive Enhanced Through Supramolecular Interaction with Tannic Acid Modified Montmorillonite

The use of soybean meal (SM) as an alternative to petroleum-based resins in wood-based panels offers a solution to the problem of formaldehyde release. However, inherent drawbacks of soybean meal adhesives, such as poor toughness, low bond strength, and susceptibility to mold, have hindered their further development. In this study, a novel biomass adhesive, SM-MMT@TA, was developed based on supramolecular interactions between tannic acid (TA), montmorillonite (MMT), and soybean meal. Tannic acid was securely attached to the MMT surface through coordination bonds with Ca2+, Mg2+, and Al3+ ions, enhancing MMT's compatibility in the matrix via strong interfacial interactions. TA on the surface of MMT@TA effectively bonded with soy protein through strong hydrogen bonding, thereby increasing the crosslink density. As a result, the adhesive exhibited a wet shear strength of up to 1.75 MPa, which represents a 143.05 % increase compared to unmodified SM adhesive. Moreover, the moisture absorption rate of the adhesive was reduced to 26.79 %. Furthermore, abundant non-covalent interactions improved the adhesive's toughness, while natural polyphenols provided additional mold resistance. Overall, this study presents a new strategy for developing renewable, high-performance biomass-based adhesives.

Innovative applications of bio-inspired technology in bio-based food packaging

Traditionally, food packaging was used to extend the shelf life of food or to monitor its condition. Inspired by many biological structures found in nature, bio-inspired functional materials for bio-based food packaging have been shown to have significantly improved capabilities over traditional bio-based food packaging materials in various aspects and to attract consumers through novel freshness preservation features. This review synthesizes recent advances in bio-inspired bio-based food packaging materials that mimic the structure of natural organisms with specific functionalities, with examples of specific biomimetics in different enhancement areas. In general, bio-based materials have certain disadvantages compared to polymer materials, so there is an urgent need for improvement and enhancement in many areas. Biomimicry further inspires the realization of enhancing some basic functions of bio-based materials for packaging (hydrophobicity, mechanical strength, antimicrobial properties, optical properties) and endowing bio-based materials with more new responsiveness and other functions. What is more interesting is that the inspiration of bionics is taken from nature, and such a perspective can also promote further progress and innovation of bio-based food packaging materials.

A synergistic strategy for formulating a facile and cost-effective soybean protein-based adhesive via co-crosslinking and inorganic hybridization

Soybean protein-based adhesives (SPAs) are environmentally friendly, sustainable, and renewable, but their wide applications are limited by moderate bonding strength, poor water resistance, undesirable flame retardancy, and high costs. Inspired by the organic-inorganic hybridization of oysters, a facile and cost-effective SPA was developed in this study via co-crosslinking branched melamine-urea-glyoxal (MUG) and polyamidoamine-epichlorohydrin (PAE) resins, as well as inorganic hybridization by using the mineral bentonite (BT). Low-cost branched MUG resins that could efficiently co-crosslink with PAE resin and substitute for 40 % expensive PAE resin were optimally copolymerized from melamine, urea, and glyoxal. This approach provided more co-crosslinkable sites for constructing denser multiple covalently-crosslinked SP-PAE-MUG networks via MUG-protein crosslinking and MUG-PAE co-crosslinking. 30 wt% of low-cost layered mineral BT was intercalated to further reinforce the mechanical properties and flame retardancy of SPA by forming a compact organic-inorganic hybridized structure. The coordination of MUG-PAE co-crosslinking and BT inorganic hybridization resulted in a cost-effective and robust SPA with a 61.2 % higher dry strength, a soaked wet strength of 126.0 %, an aged wet strength of 86.0 %, a residual carbon content after combustion of 94.3 %, and reduced the raw material cost for formulating adhesive by 19.5 % compared with controlled commercial SPA. This novel strategy highlights the potential applications of the SP in bio-adhesives and bio-composites with excellent bonding strength, water resistance, and flame retardancy.

From waste to strength: Tailor-made enzyme activation design transformation of denatured soy meal into high-performance all-biomass adhesive

Given the severe protein denaturation and self-aggregation during the high-temperature desolubilization, denatured soy meal (DSM) is limited by its low reactivity, high viscosity, and poor water solubility. Preparing low-cost and high-performance adhesives with DSM as the key feedstock is still challenging. Herein, this study reveals a double-enzyme co-activation method targeting DSM with the glycosidic bonds in protein-carbohydrate complexes and partial amide bonds in protein, increasing the protein dispersion index from 10.2 % to 75.1 % improves the reactivity of DSM. The green crosslinker transglutaminase (TGase) constructs a robust adhesive isopeptide bond network with high water-resistant bonding strength comparable to chemical crosslinkers. The adhesive has demonstrated high dry/wet shear strength (2.56 and 0.93 MPa) for plywood. After molecular recombination by enzyme strategy, the adhesive had the proper viscosity, high reactivity, and strong water resistance. This research showcases a novel perspective on developing a DSM-based adhesive and blazes new avenues for changes in protein structural function and adhesive performance.

Lobster-Inspired Chitosan-Derived Adhesives with a Biomimetic Design

Polysaccharide-based adhesives, especially chitosan (CS)-derived adhesives, serve as promising sustainable alternatives to traditional adhesives. However, most demonstrate a poor adhesive strength. Inspired by the inherent layered structure of marine arthropods (lobsters), a core-shell structure (SiO2-NH2@OPG) with amine-functionalized silica (SiO2-NH2) as the core and oxidized pyrogallol (OPG) as the shell is prepared in this study. The compound is blended with CS to produce a structural biomimetic wood adhesive (SiO2-NH2@OPG/CS) with excellent performance. In addition to thermocompressive curing, this adhesive exhibits a water-evaporation-induced curing behavior at room temperature. With reference to the design mechanism of the lobster cuticle, this microphase-separated structure consists of clustered nanofibers with varying amounts of SiO2-NH2@OPG particles between the fibers. This intriguing microphase structure and its mechanical effects could offer a powerful solution for improving the functional modification of wood composites.