"Wood on a chip"

Inspired by natural hydraulic pumps found in trees and plants, MIT engineers developed a "tree-on-a-chip" that mimics the process. A tiny chip can pump water out of a tank for days without moving parts or external pumps. Such a chip can be useful in a wide variety of applications that consume a minimal amount of energy.

By: Rinat Barko Philosopher

The group, led by Hosoi, a professor and head of operations for mechanical engineers at MIT, was looking for an efficient way to operate a pneumatic device for small robots. The ultimate goal is to create a small multi-functional robot, like Boston Dynamics' big dog robot.

The general understanding among biologists is that water molecules, driven by surface tension, rise in the sapwood canals of the tree, then diffuse through a semi-permeable membrane into the sapwood canals, which carry sugar and other nutrients to the tree cells.

The more sugar there is in the drink, the more water flows from the tip to the drink, to balance the concentration of sugar in the water. This passive process is called osmosis. In fact, engineers have previously tried to design a tree inspired by microfluidic pumps, by inventing parts that mimic the tip and the tip. But they found that these parts stopped pumping within minutes.

Hosoi's student is the one who identified a third essential part of the tree's pumping system: the leaves, which produce sugars through photosynthesis. The proposed model includes this additional source of sugars that diffuse from the leaves to the tip of a plant, and increases the sugar/water ratio, a situation that maintains a constant osmotic pressure, and causes water and nutrients to flow regularly throughout each tree.

The team of researchers was able to imitate the sap and sap pumps of the tree, and most importantly - the production of sugar in the leaves.

To produce the chip, the researchers bound together two transparent plastic plates, and drilled small channels through them to represent the acetabulum and the afferent canals. They filled the acetabulum canals with water, and the acetabulum canals with water and sugar, then separated the two plates with a semi-thick material that mimics the membrane between the acacia and the acetabulum. They then placed another membrane on top of the plates of the sap canals, and placed a sugar cube on top to represent the source of the extra sugar coming from the leaves of the tree into the sap. They connected the chip to a pipe, which fed water from a tank into the chip.

With this simple structure, the chip was able to passively draw water from the tank through the chip, and out into a glass. The flow rate was constant for several days, unlike previous designs, which pumped for only a few minutes.

Hosoi envisions that a "wood-on-a-chip" pump could be built into a small robot powered by creating hydraulic movement, without the need for pumps or moving parts.

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