High-Throughput Transpiration Up a Large Synthetic Tree*

Over the past decade, advances in nanotechnology and micro-fabrication have enabled the development of sophisticated synthetic trees that mimic the transpiration cycle of natural trees.  Current synthetic trees are scaled down for microfluidic applications, where water from a reservoir is pumped across a single micro-channel or even just held directly against the synthetic leaf material.  Here, we demonstrate that synthetic trees can be made at the same scale as natural trees, ideal for water extraction applications.  As many as 19 plastic tubes of millimetric diameter were fixed inside of a nanoporous ceramic disk on one end.  After saturating the tree by boiling it underwater, the ceramic disk was elevated over 3 m into the air while the other end of the long tubes remained submerged in a water reservoir.  A mass balance confirmed that water in the bottom reservoir was able to continuously flow up the tubes to replenish water evaporating from the ceramic disk.  A model was developed to capture the transpiration rate by coupling the Laplace equation, Kelvin equation, Poiseuille’s law, and Darcy’s law.