Drinking Lizards Lead to Targeted Transport of Lubricants


The Bionics Working Group at the RWTH Aachen Institute of Biology II is researching the surface structure of Texas horned lizards.


The Texas horned lizard has a special ability: To quench its thirst, it doesn't need to look for water sources, but rather can collect liquid on its skin. It collects small amounts of water from the environment, such as moist sand, using capillary channels between its scales. Small capillary channels then transport the water towards the lizard's snout.

The Bionics Working Group at the RWTH Aachen Institute of Biology II investigated the geometry of these channels on the skin of moisture-harvesting lizards and successfully transferred it to plastic and metal surfaces. The innovative surface structures make the passive and energy-neutral transportation of fluids in one direction possible – even against gravity.

  Man observes lizard under microscope Copyright: © Institute of Biology II (Zoology)

"The capillaries build a network and narrow towards the snout. They possess a targeted interconnection," explains Philipp Comanns, who is completing his doctorate on this topic. "Our investigations have shown that the phenomena touches on two principles. The first is the periodic and asymmetrically changing shape of the capillaries, which narrow and widen, and the second is the interconnection between the capillary channels," says Comanns.

The scientists investigated the skin of preserved lizards that the Zoological Research Museum Alexander Koenig in Bonn provided. They developed a theoretical model of how fluids behave in such capillaries and a technical prototype, which imitates nature as closely as possible. Then they lasered sawtooth-shaped capillary structures into plastic sheets. "Plastic surfaces created based on this model prohibit the flow of fluid in one direction, while they promote flow in another, even when there is small counter pressure," explains Comanns. "They behave like diodes for the fluids."

Since passive, targeted transport of fluids or lubricants is required in many technical processes, Comanns believes there is a broad spectrum of possibilities for technical application. This includes the field of microfluidics, in medical applications, distilleries, or e-ink displays. "Technical processes can be improved and resources can be saved with this method," says Philipp Comanns. "The next step is further developing the principal for specific product groups."

The work on water transport in the Texas horned lizard was published in the August issue of the Journal of the Royal Society Interface.

Source: Press and Communications