Directional, passive liquid transport: The Texas horned lizard as a model for a biomimetic 'liquid diode'
Sprache des Titels:
Moisture-harvesting lizards such as the Texas horned lizard (Iguanidae: Phrynosoma
cornutum) live in arid regions. Special skin adaptations enable them to
access water sources such as moist sand and dew: their skin is capable of collecting
and transporting water directionally by means of a capillary system
between the scales. This fluid transport is passive, i.e. requires no external
energy, and directs water preferentially towards the lizard?s snout. We show
that this phenomenon is based on geometric principles, namely on a periodic
pattern of interconnected half-open capillary channels that narrow and widen.
Following a biomimetic approach, we used these principles to develop a technical
prototype design. Building upon the Young?Laplace equation, we
derived a theoretical model for the local behaviour of the liquid in such capillaries.
We present a global model for the penetration velocity validated by
experimental data. Artificial surfaces designed in accordance with this model
prevent liquid flow in one direction while sustaining it in the other. Such passive
directional liquid transport could lead to process improvements and
reduction of resources in many technical applications.