MIT Engineers Create 'Tree-on-a-chip' to Mimic Pumping Mechanism of Plants

Trees, nature's ultra-reliable hydraulic pumps, have a constant stream of nutrients flowing through it whether its water shuttled from the roots to the leaves or sugar pumped from the leaves to the roots.

According to a report from MIT News, a group of engineers were able to design a "tree-on-a-chip" that basically functions the same way, mimicking the pumping mechanism of trees and plants. Even with no moving parts or external pumps, the chip can pump water and sugar continuously for several days.

This new mechanism can be used in robotics, powering the movement of robots with relatively cheap sugar-powered pumps inspired by trees.

"For small systems, it's often expensive to manufacture tiny moving pieces," one of the authors, Anette "Peko" Hosoi of MIT's Department of Mechanical Engineering, said. "So we thought, 'What if we could make a small-scale hydraulic system that could generate large pressures, with no moving parts?' And then we asked, 'Does anything do this in nature?' It turns out that trees do."

In trees, the pumping process goes through tissue systems called xylem and phloem. Water rises a tree's channel of xylem, then back down into channels of phloem that contains sugar and other nutrients. It self-balances: the more sugar the phloem has, the more water runs through to maintain the ratio of sugar-to-water.

For their tree-in-a-chip, the team created a system that mimics the xylem, phloem and a third important factor: the leaves, which produces the sugar through photosynthesis.

They combined two plastic slides with two channels acting as the xylem and phloem, plus a semipermeable material between the two -- just like the membrane in a real tree. Filling the xylem with water and the phloem with water and sugar, a second membrane was added over the phloem and a sugar cube placed over it to act as the leaves producing more sugar.

"The goal of this work is cheap complexity, like one sees in nature," Hosoi explained. "It's easy to add another leaf or xylem channel in a tree. In small robotics, everything is hard, from manufacturing, to integration, to actuation. If we could make the building blocks that enable cheap complexity, that would be super exciting. I think these [microfluidic pumps] are a step in that direction."

The findings are published in the journal Nature Plants.