Biology-Inspired Coating Shows Promise for Catheters

Drawing inspiration from the pitcher plant in nature, researchers at Harvard University (Cambridge, MA) have developed a material that they claim repels almost any type of liquid, including blood, even when exposed to harsh conditions. This latest breakthrough in the field of biomimetics could someday be employed in biomedical fluid handling and as a coating for catheters and other medical tubing.

Many current liquid-repellant surfaces have been inspired by the lotus plant, which features a microtextured surface on its leaves that causes liquid to bead up. However, mimicking this effect has proven to be difficult with organic or complex liquids and ineffective if the surface is damaged or subjected to extreme conditions, according to the researchers. Furthermore, the lotus effect can be somewhat expensive and difficult to replicate on a surface.

In contrast, the pitcher plant locks in water, which, in turn, yields a slick coating on its cupped leaf that serves to make insects slide right into the awaiting carnivorous plant. Seeking to mimic this effect, the Harvard scientists infused a nano/microstructured porous material with a lubricating fluid. The resulting bioinspired surfaces have been dubbed SLIPS for slippery liquid-infused porous surfaces.

"The repellent fluid surface offers additional benefits, as it is intrinsically smooth and free of defects," says lead author Tak-Sing Wong, a postdoctoral fellow at Harvard. "Even after we damage a sample by scraping it with a knife or blade, the surface repairs itself almost instantaneously and the repellent qualities remain, making SLIPS self-healing." The materials also remain almost frictionless despite exposure to extreme conditions, including high pressures, humidity, and cold temperatures.

"Not only is our bioinspired surface able to work in a variety of conditions, but it is also simple and cheap to manufacture," adds coauthor and PhD candidate Sung Hoon Kang. "It is easily scalable because you can choose just about any porous material and a variety of liquids." If commercialized, the water-repellant materials may be suited for use in such medical tubing applications as catheters and blood-transfusion systems.