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Substitutes for snail slime
20 March 2007
A team of engineers set a small robot climbing walls in order to compare how natural and artificial snail slimes work.
A snail's slime acts as both a glue and a lubricant, allowing the snail to crawl up walls and across ceilings without falling off. The snail pushes until the structure of the glue breaks, at which point it glides forwards. When the snail stops, the glue structure reforms, sticking the snail safely to the ceiling.
The team, from the Massachusetts Institute of Technology, US, and the Catholic University of Leuven, Belgium, looked at how the cycle of glue breakdown and repair works in natural snail slime and in synthetic slimes based on clay and polymers. They calculated the ideal slime properties that climbing robots would need, and found a wide range of likely candidates, including hair gel and peanut butter.
Snail slime acts as both a glue and a lubricant
'Who would have thought that snails could use other soft solids such as mayonnaise or axle grease as an adhesive lubricant to climb up vertical walls?' said Christian Clasen, who worked on the study.
Co-worker Randy Ewoldt said, 'an important result is that snail mucus per se is not required for robots to climb walls. We can make our own adhesive locomotion material with commercial products instead of harvesting slime from a snail farm.'
Ewoldt has first hand knowledge of the challenges involved in collecting snail slime. 'I would entice a slug or snail with a piece of lettuce to crawl across a glass plate, and on the good days it would cooperate and leave enough of a slime trail for me to collect and place in the rheometer for testing,' he said.
Link to journal article
Rheological fingerprinting of gastropod pedal mucus and synthetic complex fluids for biomimicking adhesive locomotion
Randy H. Ewoldt, Christian Clasen, A. E. Hosoi and Gareth H. McKinley, Soft Matter, 2007, 3, 634