NATURE IS THE BEST ENGINEER
When we talk of great engineering and meticulous design, there is no engineer as good as Nature itself. For example, think of how a tree functions: In the first step, roots absorb nutrients from the soil until the concentration of minerals in the roots is higher than the soil.
This marks the onset of osmosis and water enters into the root. While the water enters, it is pulled up the sap via xylem to the rest of the tree. In order to complement this mechanism, when the leaves breaths and spends water, a cohesion tension takes place which helps the sap flow.
The other mechanism is related to the transport of complex sap (product of the photosynthesis) to the rest of the tree. During photosynthesis, leaves generate a greater concentration of sugar than the roots for example. In order to find a balance, osmosis occurs, prompting the leaves to receive water.
When the water arrives, it pushes the sap via the phloem, sending it to the rest of the tree. The water from the xylem system and the phloem system inter-communicates via a semipermeable membrane, creating a closed loop.
Beautiful, isn’t it?
SYNTHETIC TREE ON A CHIP
Researchers have used nature as their inspiration to successfully create a synthetic tree on a chip. In a recent paper published in Nature Plants, scientists from MIT and collaborators developed a pump for sugar and water that works in a way very similar to the plants’ mechanism.
The scientists mimic this mechanism in order to have a chip microfluidic pump without any mechanical parts.
“The pump’s passive pumping may be leveraged as a hydraulic actuator for very small robots,” says Prof. Anette ‘Peko’ Hosoi, Department of Mechanical Engineering, MIT. This is a great advantage, as it is very hard and expensive to make very small mechanical parts, adds Prof. Hosoi.
The MIT design for tree on a chip consists of two plastic slides together with small channels to represent the xylem and the phloem. The “phloem” was filled with sugary water, while the “xylem” was filled only with water. Between the two, they put a membrane to close the loop.
On the side of the phloem, they put another membrane and a cube of sugar, in order to represent the leaf and photosynthesis. Finally, they connect the chip with a water tank.
With this experimental setup, they were able to run the pump for several days. In previous experiences, without the sugar source (“the leaf”), the pump was only able to run for several minutes. In that sense, it is possible to foresee that in the future we could have a small robot that runs with sugar as its only fuel.
This research could be a first step towards what may be a great revolution in the future, because we can avoid mechanical parts which, in general, are more susceptible to ageing and we can use sugar as an energy source, a natural resource that is widely available all over the world.
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