Theoretical Exploration of Barrel-Shaped Drops on Cactus Spines.

To survive an arid environment, desert cacti are capable of harvesting water from fog by transporting condensed water drops using their spines. Cactus spines have a conical shape. In this work, on the basis of the difference of liquid pressure, a new theoretical model has been developed for a barrel-shaped liquid drop on a conical wire. This model is further simplified to interpret the effects of contact angles, conical angle, surface microgrooves, and gravity on the drop movement along a cactus spine.

[1]  C. Luo,et al.  Separation of oil from a water/oil mixed drop using two nonparallel plates. , 2014, Langmuir : the ACS journal of surfaces and colloids.

[2]  Liejin Guo,et al.  Experimental study on directional motion of a single droplet on cactus spines , 2015 .

[3]  Cheng Luo,et al.  Branched ZnO wire structures for water collection inspired by cacti. , 2014, ACS applied materials & interfaces.

[4]  Lei Jiang,et al.  Bioinspired Conical Copper Wire with Gradient Wettability for Continuous and Efficient Fog Collection , 2013, Advanced materials.

[5]  R. N. Wenzel.  RESISTANCE OF SOLID SURFACES TO WETTING BY WATER , 1936 .

[6]  K. Stebe,et al.  Equilibrium shapes and locations of axisymmetric, liquid drops on conical, solid surfaces , 2006 .

[7]  S. Moon,et al.  Contact angles of liquid drops on super hydrophobic surfaces: understanding the role of flattening of drops by gravity. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[8]  Stephen Michielsen,et al.  Gibbs free energy of liquid drops on conical fibers. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[9]  Y. Tsori.  Discontinuous liquid rise in capillaries with varying cross-sections. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[10]  A. Adamson.  Physical chemistry of surfaces , 1960 .

[11]  B. Carroll,et al.  Equilibrium conformations of liquid drops on thin cylinders under forces of capillarity. A theory for the roll-up process , 1986 .

[12]  Lei Jiang,et al.  A multi-structural and multi-functional integrated fog collection system in cactus , 2012, Nature Communications.

[13]  B. Carroll.  The accurate measurement of contact angle, phase contact areas, drop volume, and Laplace excess pressure in drop-on-fiber systems , 1976 .

[14]  Cheng Luo,et al.  Behavior of a liquid drop between two nonparallel plates. , 2014, Langmuir : the ACS journal of surfaces and colloids.

[15]  D. Quéré,et al.  Drops on a conical wire , 2004, Journal of Fluid Mechanics.