Gecko-inspired adhesion controlled by light | January 23, 2017 Issue - Vol. 95 Issue 4 | Chemical & Engineering News
Volume 95 Issue 4 | p. 4 | News of The Week
Issue Date: January 23, 2017 | Web Date: January 19, 2017

Gecko-inspired adhesion controlled by light

Adhesive grips and releases objects thanks to UV-triggered azobenzene chemistry
Department: Science & Technology
News Channels: Materials SCENE
Keywords: adhesives, gecko, azobenzene, bioinspired, photoresponsive, UV light
[+]Enlarge
Under UV light, azobenzene (R = various groups) changes conformation from trans to cis, allowing the adhesive to lift up.
Credit: Sci. Robotics
As UV light moves the azobenzene molecule from trans to cis configuration, the adhesive curls up away from the surface.
 
Under UV light, azobenzene (R = various groups) changes conformation from trans to cis, allowing the adhesive to lift up.
Credit: Sci. Robotics

A team of German researchers have created an adhesive pad inspired by the sticky feet of geckos that unsticks from objects when triggered by ultraviolet light. The pad could lead to robotic fingers controlled by light that can pick up and release delicate objects.

[+]Enlarge
Credit: Shutterstock
A picture of a green gecko.
 
Credit: Shutterstock
[+]Enlarge
Credit: Shutterstock
A picture of a brown gecko.
 
Credit: Shutterstock

Geckos can scurry up and down walls thanks to about half a million fibers called seta on each of their feet. Each setae is divided into hundreds of spatula-like nanostructures that individually grip a surface through weak van der Waals interactions. Collectively, these millions of interactions lead to strong adhesion.

In the new work, Emre Kizilkan of Kiel University and his colleagues used previously developed surfaces with mushroom-shaped polydimethylsiloxane microstructures to produce geckolike adhesion. But for easy manipulation, they desired a system that could attach and detach its adhesive hold at will. “We wanted to control the adhesion by light,” Kizilkan says.

To do so, the team incorporated a stretchy liquid crystalline elastomer layer containing azobenzene molecules underneath the adhesive pad. Azobenzene undergoes a trans to cis isomerization in the presence of UV light, which causes the adhesive layers to bend (Sci. Robotics 2017, DOI: 10.1126/scirobotics.aak9454). The layers revert to normal when the researchers turn off the UV light.

When the adhesive surface lies flat against an object, it sticks. Under UV illumination, the adhesive bends, releasing the bulk of its contact with the object, relinquishing its grip. Kizilkan showed that the device could move objects such as glass beads and glass slides.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

Leave A Comment

*Required to comment