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Sci Tech
New materials for adhesives, optics, coatings
Through a combination of geometry and materials selection, the Venus flytrap’s leaflets snap from concave to convex when an object triggers their hairs. The key to the flytrap’s ability to capture prey is the speed and sensitivity that accompany a ‘snap’ transition.
Natural phenomenon
For the Venus flytrap, the transition occurs in roughly 100 milliseconds. Inspired by this natural phenomenon, Alfred Crosby and his doctoral candidate Douglas Holmes of the University of Massachusetts Amherst’s polymer science and engineering department created a polymer surface covered with small holes capped by thin lenses of the same material.
The lenses can snap between convex and concave when triggered and the ‘snapping surfaces’ can snap at least as fast as 30 milliseconds.
Even more important is the fact that this speed can be easily adapted for faster or slower transitions depending on the final use.
Imagine paint that adheres to a surface but releases on command, or road signs that change their reflectivity with changing weather conditions. These are two potential uses of this novel, responsive material.
Environment-friendly
The research was published online recently in the journal Advanced Materials. “This material’s design could allow for the removal of superglues, wallpaper and paints without toxic solvents, which would be an advantage for the environment,” says Crosby.
Snap transition
This ‘snap’ transition changes the surface of the material from a series of mounds to a series of depressions, a strategy that has great potential for creating release-on-command coatings, ‘smart’ adhesives, adaptable optical devices or surfaces with responsive reflective properties, according to a University of Massachusetts Amherst press release.
The triggers
Currently Crosby and Holmes have demonstrated mechanical pressure, swelling and surface chemistry as triggers for the ‘snap’ transition.
The connection to controlling adhesion with the responsive ‘snapping’ surfaces is fuelled by another project in Crosby’s research group that is focused on understanding and mimicking the gecko, a small lizard with pattern-covered toes that provide enhanced adhesion and release properties.
The ‘snapping surfaces,’ which are really Venus flytrap-gecko hybrids, can be turned into smart adhesives by covering the lenses with hairs that adhere in the convex position and release when the lenses are concave.
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