An airplane model assembled with silk glue. Image credit: Marco Lo Presti of Tufts University

Silk protein forms fibers, cross-links, and iron complexes, similar to those used by marine organisms.

If you have ever tried to cut mussels from seawalls or barnacles from the bottom of a boat, you will understand that we can learn a lot from nature about how to make strong adhesives. Engineers at Tufts University noticed that a new type of glue inspired by those stubbornly adhering crustaceans was reported in the journal Advanced Science today.

Starting with fibroin harvested from silkworms, they were able to replicate the key features of barnacle and mussel glue, including protein filaments, chemical cross-links and iron bonds. The result is a powerful non-toxic glue that is as strong underwater as it is in dry conditions, and stronger than most synthetic glue products on the market today.

"The composite material we created is not only better underwater than most of the adhesives available today, but also uses less material to achieve this strength," Tufts Institute of Engineering Professor of Engineering and Tufts Silk Lab Director Fiorenzo Omenetto said where the material was created and the corresponding author of the study. "And because this material is made from extracted biological sources, and the chemical composition is benign — taken from nature, to a large extent, avoiding synthetic steps or the use of volatile solvents — it is also in terms of manufacturing Advantages."

Silklab's "glue workers" focus on a few key elements to replicate in aquatic adhesives. Mussels secrete long sticky filaments called byssus. These secretions form polymers, which are embedded in the surface, and chemically cross-linked to strengthen the bond. Protein polymers are composed of long-chain amino acids, one of which is dihydroxyphenylalanine (DOPA), which is an amino acid containing catechol that can be cross-linked with other chains. Another special ingredient added to mussels-iron complex-can enhance Bezos' cohesion.

Barnacles secrete a strong cement made of protein, and these binders form a polymer that is fixed to the surface. The proteins in barnacle cement polymers fold their amino acid chains into beta sheets-a zigzag arrangement that presents a flat surface and has many opportunities to form with the next protein in the polymer or the surface formed by polymer filaments Strong hydrogen bonds are being attached.

Inspired by all these molecular bonding techniques used by nature, Omenetto's team set out to replicate them and use their chemical expertise in silk fibroin extracted from silkworm cocoons. Silk fibroin has many of the shapes and bonding properties of barnacle cement, including the ability to assemble large β-sheet surfaces. The researchers added polydopamine, a random polymer of dopamine that presents cross-linked catechols along its length, just like the adhesive filaments used by mussels to cross-link them. Finally, the adhesive strength is significantly improved by curing the adhesive with ferric chloride to ensure the bond between catechols, just like they do in natural mussel adhesives.

"The combination of silk fibroin, polydopamine, and iron binds the same bonding and cross-linking levels together, making these barnacle and mussel adhesives so strong," a postdoctoral scholar in Omenetto's laboratory, the first of the study Author Marco Lo Presti said. "We ended up with an adhesive that even looked like its natural counterpart under the microscope."

Obtaining the right mixture of acidic conditions for the curing of silk fibroin, polydopamine and iron ions is essential for the adhesive to cure and work underwater, reaching 2.4 MPa (megapascals; per square inch) Pounds) strength. This is better than most existing experimental and commercial adhesives, which is only slightly lower than the strongest underwater adhesive at 2.8 MPa. However, this adhesive has an additional advantage, that is, it is non-toxic, composed of all natural materials, and only needs 1-2 mg per square inch to achieve bonding-just a few drops.

Professor Gianluca Farinola, a collaborator, said: “The combination of possible safety, conservative use of materials, and superior strength demonstrates its potential utility in many industrial and marine applications, and may even be suitable for consumer-oriented model building and Home use and other fields." Research at Barry Aldo Moro University, Adjunct Professor of Biomedical Engineering at Tufts University. "In fact, we have used silk fibroin as a biocompatible material for medical purposes, which has prompted us to explore these applications," Omenetto added.

Since I was a kid in the 1960s, I have been reading about the development and "breakthroughs" of mussel binders. However, have these affected the market?

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