Underground Water Extraction Using Synthetic Trees.

Unlike traditional well pumping from bulk reservoirs, trees can extract and elevate water spontaneously from moist soil. Here, we demonstrate transpiration-driven underground water harvesting by burying the bottom of a synthetic tree in water-saturated soil while encasing the nanoporous leaf within a condensing still. Evaporation from the leaf facilitates the continual transport of water up the tree's tubes, with a cold plate on the condensing still converting the vapor back to liquid. A hydraulic model balances the negative Laplace pressure generated within the leaf against the hydrostatic pressure and viscous losses in the leaf and soil. We show that the evaporation-limited transpiration rate, and by extension the water harvesting rate, can be directly tuned through controlled heat inputs.