Tag Archives: biomimicry

Slippery and Slick

Carnivorous pitcher plants are one inspiration for super-hydrophobic surfaces

The integration of engineered hydrophobic surfaces in everyday life is all around us: Teflon cookware in the kitchen, Rain-X in windshield wipers, and NanoDrop at the bench (hint: the sample pedestal coating). Unfortunately, there is much to be desired regarding the attributes of even the best industrially marketed treatments. One major challenge is that many of these surfaces have poor anti-fouling properties, are not optically transparent, and do not repel low-temperature and oily liquids. This technological dearth has broad impacts, from the medical industry to aeronautics. While it may seem like the Gore-Tex on your winter jacket is working just fine, there are a series of demanding applications that require an extra level of resilience to bacterial films. For instance, bacterial infections from medical catheters remain a leading cause of complications for chemotherapy patients due to tubes that provide insufficient protection from bacterial growth.

Last week in Nature,  the Varanasi group at MIT reported a new superhydrophobic material that has the potential to make surfaces drier than ever before. The scientists at MIT were inspired by the microscopic ridges present in the leaves of the the nasturtium plant to develop a robust superhydrophobic mesh that is capable of quickly repelling water and even molten metal. Read on to explore the world of wettability and the remarkable biology that inspire these technologies.

Leaping lizards

Do animal tails assist with “in-flight” stabilization?  It’s probably not a question you ponder every day, but it’s exactly what Berkeley graduate student researchers Thomas Libby and Evan Chang-Siu set out to find when they built a tailed robot  and drove it off a ramp.

Libby and Chang-Siu’s project made news when their paper Tail-assisted pitch control in lizards, robots, and dinosaurs made the cover of the latest issue of Nature. Their project is one of many exciting biomechanics projects underway in Berkeley’s Center for Interdisciplinary Bio-inspiration in Education and Research, or CiBER, led by Integrative Biology professor Dr. Bob Full.

Inspired by the observation that Red-headed Agama lizards stabilize themselves in free-fall with controlled movements of their tails, the researchers built a lizard-sized robot with wheels and a “tail” (metal rod) and tried to  mimic the ability to stay upright during a fall. Unlike previous attempts to build self-righting robots, their robot tail used a control mechanism called active feedback.  Active feedback occurs when the robot is able to respond to its environment by making instantaneous movements in accordance to the in-motion changes perceived by its sensors.  In contrast, previous work focused on feed-forward robots, which rely on pre-programmed movements to compensate a predetermined trajectory. Tom Libby explains the difference in terms of picking up a milk jug: if you expect the jug to be full, you will initiate an appropriate amount of muscle power as you pick up the jug; this is feed-forward.  If, upon picking up the jug, you realize that it is empty, the system you use to change the amount of power you input (thereby preventing yourself from getting smacked in the head with the jug) is feedback control.