July 12, 2024

Plant-based Glue Gets Stronger Underwater

A team of researchers at Indiana’s Purdue University has developed a bio-based glue that not only works underwater but becomes stronger when immersed. The adhesive, made mainly of zein and tannic acid, has the potential to be utilized in various industries, including construction, biomedical, dental, and coral reef restoration.

Getting glue to stick in dry conditions is relatively simple, but maintaining a bond underwater has always been a challenge. However, Assoc. Prof. Gudrun Schmidt and her colleagues have found a solution by developing a nontoxic adhesive that gets stronger when submerged in water. The glue is primarily made from zein, a protein extracted from corn, and tannic acid derived from galls in oak tree bark.

When the glue is applied and sandwiched between two objects underwater, a thin skin forms on its surface. This skin can easily be broken by piercing it with a finger or a similar object, allowing the surrounding water to enter the glue and increase its bond strength. The maximum bonding effect occurs at a water temperature of approximately 30 ºC (86 ºF).

While the exact mechanism behind this reaction is not fully understood, Schmidt explains that tannic acid is primarily responsible for adhesion to surfaces. The structure of the acid’s molecules bears similarities to the natural glue used by mussels to cling to rocks underwater.

The process of applying the glue resembles that of preparing a poached egg. When a raw egg is placed in warm water, a thin skin forms around it while the inside remains raw. If the water is warm but not too hot, the skin around the egg is delicate and can be easily broken with the tip of a fork. Applying the poached egg analogy, sandwiching the glue between two substrates mimics squeezing a poached egg between two slices of bread.

In addition to its underwater bonding properties, the glue is easy to produce outside of a laboratory setting using cost-effective and sustainably sourced ingredients. Schmidt believes that it could be a gamechanger in multiple applications, such as the construction industry, biomedical and dental procedures, and even the restoration of coral reefs.

The development of this plant-based glue marks a significant advancement in underwater adhesion technology. Its ability to strengthen bonds when submerged opens up possibilities for numerous industries where maintaining adhesion in wet conditions is essential. As further research is conducted, this bio-based adhesive could revolutionize industries and contribute to environmentally friendly solutions for various applications.

1. Source: Coherent Market Insights, Public sources, Desk research
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