Researchers have developed moisture-responsive, shape-morphing, slippery, graphene smart surfaces using ultrafast laser treatment.
This combination of functional properties in single, bio-inspired surfaces could benefit applications in environmental sensing, such as rainfall droplet collection and manipulation.
The new hybrid surfaces could also be used to directly harness energy from naturally occurring or engineered water evaporation, which could subsequently be converted into mechanical energy or electricity. This could have implications in the development of weather-responsive architectural systems, smart textiles, or bionic robots.
The scientists, from Jilin University in China, have taken inspiration from carnivorous plants, which can trap and digest small insects using one of two mechanisms: active trapping and passive trapping. For example, the Nepenthes pitcher plant catches insects through a passive trapping mechanism via lubricant-infused slippery surfaces, while the Dionaea muscipula performs active trapping through a sophisticated actuating mechanism.
While surfaces exhibiting each of these properties have been developed individually in the past, until now, according to the researchers, combining such properties in a single surface has remained challenging.
In Opto-Electronic Advances they describe their overcoming of such challenges using photoreduction techniques induced via femtosecond laser direct writing and simultaneous structuring. Such techniques were used to prepare a graphene oxide (GO) and laser-reduced graphene oxide (LRGO) bilayer actuator that deforms dynamically under moisture actuation. A lubricant-infused slippery surface was then integrated with the actuator by immobilising lubricant at the LRGO side via capillary forces.
The result was a hybrid, moisture-responsive, shape-morphing, slippery surface demonstrating both active catching and passive trapping capabilities.
With it the scientists have since developed a “smart frog tongue” that can catch and manipulate droplets containing live tubificidaes. The slippery surface can bend under moisture actuation, get in touch with the droplet, and let it slide to the bottom of the structure.
“The LRGO/GO actuator demonstrated large deformation curvature, short response/recovery time, and improved stability,” the researchers explained in their announcement of the work. “The moisture-responsive, shape-morphing slippery surface reveals great potential for developing bionic robots.”
For more information on this work, see the original paper published in Opto-Electronic Advances.