Adhesive by Nature
Nature is a laboratory of superlatives and is full of organisms that produce adhesives with breathtaking properties.
From photosynthesis to the lotus leaf: Nature creates extraordinary eccentricities – They amaze us, and sometimes literally turn us ‘green’ with envy. Scientists are working on developing substances and products that mimic natural wonders. And they are doing so successfully, as the invention of self-cleaning surfaces with the famous ‘Lotus Effect’ shows. When it comes to “adhesive substances with multiple properties and for all kinds of purposes”, nature offers a well-stocked research fund. Where there is life … there is adhesive power.
For example, sugar: As a chemical substance class, a sub-group of carbohydrates, at the cellular level, sugar is the energy store par excellence and is vital for flora and fauna. But that’s not all: Under certain conditions, sugar can also work as an efficient adhesive. Every child who has licked his or her sticky fingers after eating candyfloss knows this from experience. Because if, for example, through moisture, the water and oxygen contained in the sugar crystals are separated from each other, the hydrogen, which is reactive, wants to bond again and adheres to everything it finds.
“Everything that is based on sugar is ultimately adhesive.”
When it comes to adhesives, the animal and plant kingdom offers an all-in-one solution for every purpose. Super adhesive and yet reversible? The slime of slugs proves that it is possible. Long-lasting adhesive strength under water, but also on dry land? Barnacles and mussels have used this successfully for millions of years. Removable without leaving a trace, but adheres to smooth surfaces as well as to rough surfaces? Gecko feet can do that for an entire gecko life.
Customised adhesive strength, removable and, at best, even reusable: tesa products such as tesa Powerstrips® and smart fastening systems are already combining these basic properties. However, issues such as sustainable production and biodegradability also play an ever more important role. “With paper-based packaging tapes and solvent-free manufacturing processes, we are moving closer to nature. However, there is so much more to it,” says innovation manager Bastian Brinkmann, looking to the future of a still relatively young research and development field.
“Nature can act as a role model in two ways: With a view to innovative, high-performance solutions, but above all when it comes to sustainability.”
Superman, superpowers, super glue – we dream about the possibilities of the seemingly impossible. Spinning it a different way: The webs of the orb-weaver spider defy wind and weather. Neither UV light nor rain can impair their functionality. Such a robust ‘network’ is the magic weapon of the science-fiction hero Spiderman. But even in down-to-earth adhesive research, the question is how people can use the superpowers of the sticky spider secretion. Polymer scientists from the University of Akron (USA) came closer to answering the question of how it sticks reliably even in conditions of elevated humidity: Hygroscopic components in the secretion absorb moisture and render it harmless to the web structure.
Another example of the search for the advantages of bio-adhesive developments is a multi-year project at the TU Hamburg (Germany), one of whose partners is tesa. The project involves research into the wood component lignin, for example for use in adhesives. The most common polymer in nature can be an alternative to petroleum-based applications. As opposed to the fossil raw material, lignin sources such as wood or straw are renewable raw materials that can be grown, and when they are burned, they only emit as much carbon dioxide as they have stored.
Studies on the biochemical structure of natural adhesive occurrences, their precise properties, their benefits, and their potential applicability are just at the beginning. However, it’s a very promising beginning, as previous findings and developments show. When drying, viscous snail slime creates a strongly adhesive, firm bond to surfaces. As soon as the mucus liquefies, this bond can easily be broken. In 2019, scientists at the University of Pennsylvania (USA) succeeded in developing a polymer gel with similar properties. Depending on the water content, it changes from a releasable-elastic mass into the glass-like hard mass of a super glue and vice versa. In their search for innovations, the tesa laboratories identified an exciting technology with gecko-like adhesive properties. Solutions for residue-free removal and repeated use on various substrates, even on rough and dirty surfaces, are getting closer to reality.