There are few things more environmentally devastating than an oil spill, and the consequences last for years after the initial disaster. All that oil isn’t easy to clean up, despite the best efforts of humans, but nature might have an answer, as it does for so many things. Researchers at the University of Southern California are studying the structure of a particular leaf to fabricate a material that, made in large quantities, could much more easily remove oil than anything being used today.
Salvinia molesta is a floating fern native to South America. Its leaves are extremely hyrdophobic and retain a surrounding pocket of air when submerged in water, thanks to tiny water-resistant hairs.
“I think the reason the plant’s surface is super-hydrophobic is because it lives on the water and requires air to survive,” said postdoctoral researcher Yang Yang. “If it weren’t for the long-term evolution of this plant, the plant could be submerged in water and would die.”
On a microscopic level, the leaf hairs align in a structure that resembles an egg beater or whisk. Using a method called immersed surface accumulation 3D printing (ISA 3D printing), the researchers were able to recreate this egg beater microstructure, called the Salvinia effect, using plastic and carbon nanotubes. The result was a material that was both highly hydrophobic and olephilic, or oil-absorbing. The combination allows oil and water to be efficiently separated.
The research team hopes that eventually the material, which they have 3D printed as a prototype, can be manufactured on a large enough scale to be used to separate oil from water in the ocean. Right now, the methods used for doing so require huge amounts of energy in the form of an electric field or mechanically applied pressure.
“We tried to create one functional surface texture that would be able to separate oil from water,” said Associate Professor Yong Chen. “Basically, we modified the surface of the materials by using a 3-D printing approach that helped us achieve some interesting surface properties.”
The Salvinia effect could also be used in other applications, including medical ones. It has the potential to be used for microdroplet manipulation, in which adhesion of liquid to a robotic arm can be tuned accordingly and result in non-loss transfer of tiny amounts of liquid. The technique can be used in several different applications, including droplet-based microreactors, nanoparticle synthesis, tissue engineering, drug discovery and drug delivery monitoring.
One possible application of high-performance microdroplet manipulation could be more efficient blood analyses for patients. A robotic gripper could move to different stations and dispense microdroplets of blood, which would then be evenly mixed with different chemicals for testing. Those tests could also be designed to control the ratio of chemical to droplet and could conserve source materials and chemical reagents.
“You can have a robotic arm with a gripper made to mimic ‘Salvinia effect,'” said PhD student Xiangjia Li. “No matter which way you move the arm, the gripping force is so large that a droplet will stay attached.”
The research has been published in a study entitled “3D-Printed Biomimetic Super-Hydrophobic Structure for Microdroplet Manipulation and Oil/Water Separation,” which you can access here. Authors include Yang Yang, Xiangjia Li, Xuan Zheng, Zeyu Chen, Qifa Zhu, and Yong Chen.
Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below.[Source: University of Southern California]