Complex Made Simple

Could nano-bionics make plants replace light bulbs, and talk to us?  

In December of 2017, researchers at MIT announced they had found a way to create light-emitting plants. They achieved this by embedding specialized nanoparticles into leaves 

The specialized nanoparticles contain the enzyme luciferase, a substance found in light-emitting fireflies Plants use hydrogen peroxide to communicate within their leaves Living plants are literally "green" power sources, which may become one of the future's electricity supplies

In December of 2017, researchers at MIT announced they had found a way to create light-emitting plants. They achieved this by embedding specialized nanoparticles into the leaves of watercress plants that allowed them to give off a very dim light for nearly four hours.

It was believed that with further optimization, these plants could one day be bright enough to illuminate a home or office.

Today, MIT engineers have upgraded their light-emitting plants to be able to be charged by a LED in just 10 seconds, glow 10 times brighter than their first generation of plants, and last for several minutes. They can even be recharged repeatedly.

The specialized nanoparticles contain the enzyme luciferase, a substance found in light-emitting fireflies. This process is an example of the emerging field of “plant nano-bionics,” wherein researchers develop ways to augment plants with novel features. 

In order to make their plants glow longer, MIT created and used a “light capacitor,” which is normally the part of an electrical circuit that can store photons and release them when needed.

The researchers showed that after 10 seconds of blue LED exposure, their plants could emit light for about an hour. The light was brightest for the first five minutes and then gradually diminished. The plants can be continually recharged for at least two weeks.

The MIT researchers found that the “light capacitor” approach can work in many different plant species, including basil, watercress, and tobacco. They also showed that they could illuminate the leaves of a plant called the Thailand elephant ear, which can be more than a foot wide, a size that could make the plants useful as an outdoor lighting source.

The researchers also investigated whether the nanoparticles interfere with normal plant function. They found that over a 10-day period, the plants were able to photosynthesize normally and to evaporate water through their stomata.  

Stressed leaves

MIT engineers have also developed a way to closely track how plants respond to stresses such as injury, infection, and light damage, using sensors made of carbon nanotubes. These sensors can be embedded in plant leaves, where they report on hydrogen peroxide signaling waves.

Plants use hydrogen peroxide to communicate within their leaves, sending out a distress signal that stimulates leaf cells to produce compounds that will help them repair damage or fend off predators such as insects. The new sensors can use these hydrogen peroxide signals to distinguish between different types of stress, as well as between different species of plants.

That means that, in real-time, one can see a living plant’s response, communicating the specific type of stress that it’s experiencing.

This kind of sensor could be used to help agricultural scientists develop new strategies to improve crop yields. The researchers demonstrated their approach in eight different plant species, including spinach, strawberry plants, and arugula, and they believe it could work in many more.

Green power

The interdisciplinary team of roboticists and biologists at IIT-Istituto Italiano di Tecnologia in Pontedera (Pisa, Italy), found that living plants can help with electricity. Fabian Meder, Barbara Mazzolai, and their coworkers at IIT discovered that living plants are literally “green” power sources, which may become one of the future’s electricity supplies that perfectly integrates into natural environments and is accessible all over the world. Researchers discovered that plants can generate, by a single leaf, more than 150 Volts, enough to simultaneously power 100 LED light bulbs. Researchers also showed that a “hybrid tree” made of natural and artificial leaves can act as an innovative “green” electrical generator converting wind into electricity.

Certain leaf structures are capable to convert mechanical forces applied at the leaf surface into electrical energy. The leaf is able to gather electric charges on its surface due to a process called contact electrification. These charges are then immediately transmitted into the inner plant tissue. The plant tissue acts similar to a “cable” and transports the generated electricity to other parts of the plant. Hence, by simply connecting a “plug” to the plant stem, the electricity generated can be harvested and used to power electronic devices.

Researchers additionally describe for the first time how this effect can be used to convert wind into electricity by plants. Therefore, researchers modified a Nerum oleander tree with artificial leaves that touch the natural N. oleander leaves. When wind blows into the plant and moves the leaves, the “hybrid tree” produces electricity. The electricity generated increases the more leaves are touched. Consequently, it can be easily up-scaled by exploiting the whole surface of the foliage of a tree or even a forest.