Unlocking the secret of the slime

04.03.2016
© Simon Kuster
© Simon Kuster
© Simon Kuster

Superabsorbent polymers (SAPs), in combination with nonwoven fabrics, have revolutionised absorbent hygiene products over the past decade; and are in themselves now an industry worth over $7 billion annually.

Baby diapers represent the key end-use for SAPs, with healthy growth predicted over the coming years, while the adult incontinence market is becoming increasingly significant.
SAPs are quite remarkable in their ability to absorb up to 500 times their own weight (between 30-60 times their volume) and have been instrumental in allowing manufacturers to make lighter weight products with all the advantages this brings. The very latest components for these products will be extensively showcased at INDEX™17 in Geneva.

Now, however, Swiss scientists believe even more effective SAPs might be possible – although revealing the source of them may be a difficult sell to the diaper brands and their consumers.

The Atlantic hagfish has been around for 300 million years, outlived the dinosaurs and survived catastrophic meteorite impacts, warm phases and glacial periods. Even today, it continues to populate the sea at depths where it eats carrion and hunts prey.

It is not the most attractive of sea creatures – nor is the viscous, elastic exudate it secretes when attacked by a predator.

The properties of this slime, however, have attracted the attention of researchers at the ETH Laboratory of Food Process Engineering in Zurich.

Hagfish slime gels within a split second to form a massive mass – even in cold water. This immobilises vast amounts of water, forming a dilute, viscous and cohesive network. As a consequence, fish attempting to attack a hagfish are very likely to start suffocating in it and release their prey.

A three-year ETH research project, supervised by Dr Simon Kuster, is now focusing on the properties of the slime, after earlier research confirmed that it consists of two main components – 15-30-centimetre-long protein threads and mucin, which sits between the threads. The protein threads have properties similar to spider silk and are extremely tear-resistant and elastic, although only when moist.

The slime consists of almost 100% water, containing just 0.004% gelling agent. This means the weight ratio of gelling agent to water is 26,000-fold – over 200 times more than in conventional animal gelatine. Furthermore, very little energy is required for the gelling process.

The ETH researchers were especially fascinated by the protein filaments, a sphere which measures 150 micrometres in diameter while still in the glands, but which extends to threads of several centimetres in length once part of the slime. How the threads unwind from the sphere is not yet fully understood.

Kuster and his team have now partnered with a Norwegian company authorised to catch Atlantic hagfish in the wild and keep them in an aquarium – in order to further their quest to unlock the secret of the slime, and perhaps one day develop an even more super superabsorbent.

 

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