Someday in the near future you could be reading by the light of your favorite plant — no cord or electrical outlet needed. This could be a real energy-saver, not to mention great during a power failure. And it’s not as far-fetched as it seems.
Scientists at the Massachusetts Institute of Technology have successfully engineered plants to glow, causing them to emit a dim light for nearly four hours. The researchers believe that further tinkering could create plants bright enough to illuminate a workspace, and might even eventually turn trees into self-powered streetlights.
The process involves embedding the plants with specialized nanoparticles that induce them to give off light. Not only that, the energy used to power the light comes from the plant itself.
The initial experiments were conducted on spinach, arugula, kale and watercress, thus “people can eat salad and light their dinner table at the same time,” joked MIT postdoctoral fellow Seon-Yeong Kwak, lead author of a study published in the journal Nano Letters that described the process. But seriously, “there is nothing that prevents us from considering other plant species. We are hard at work on the next generation of light-emitting plants and these will be brighter and have a longer duration,” she said.
The immediate goal of the work is to produce plants that can provide low-intensity indoor lighting. “The vision is to make a plant that will function as a desk lamp — a lamp that you don’t have to plug in,” said Michael Strano, professor of engineering at MIT and the study’s senior author. “The light is ultimately powered by the energy metabolism of the plant itself.”
The global energy consumption from direct and indirect lighting accounts for nearly 20 percent of demand and more than two gigatons of carbon dioxide emissions, according to Kwak. “This demand, coupled with the unprecedented rapid growth of cities and urbanizing regions around the world, is changing the ways in which urban infrastructure is conceived of, powered, delivered and maintained,” she said.
There are no viable solutions to the challenges of finding sources for lighting technologies, urban lighting implementation, power, maintenance and disposal of batteries, bulbs, semiconductor circuits, chips and other streams of e-waste and hardware that result from traditional bulb-based grid lighting, Kwak said. “Plant-based lighting would be a tremendous and profoundly impactful global energy revolution” that is safe, renewable and compostable, she said.
While the research did not conduct a sustainability analysis, nor a comparison between conventional and plant-sourced lighting, “the plant as a light source is doubly carbon negative, as plants consume CO2 in their fuel production and they, themselves, are the product of carbon fixation from the atmosphere,” she added.
Plant nanobionics is a new research area pioneered by Strano’s lab that seeks to provide the plants with innovative features that the scientists hope will assume many functions now performed by electronic devices. The researchers earlier designed plants that can detect explosives and send that information to a smartphone, as well as plants that can monitor drought.
To make their plants glow, the MIT team turned to luciferase, the same enzyme used by fireflies. Luciferase acts on a molecule called luciferin, causing it to give off light, while a second molecule, known as co-enzyme A, boosts the process by eliminating a byproduct that inhibits luciferase activity.
The scientists put each component into different nanoparticles, which carried them to the right part of the plant, and helped regulate their amount. (If the concentration of the molecules is too heavy, it can be toxic to the plants.) To get the particles into plant leaves, the researchers first suspended the particles in a solution, then immersed the plants, and then exposed the plants to high pressure. The pressure forced the particles into the leaves through tiny pores called stomata.
Early attempts produced plants that glowed for about 45 minutes. Further tweaking has improved that time to 3.5 hours. The light generated by one 10-centimeter watercress seedling is currently about one-thousandth of the amount needed to read by, but the researchers are confident they can increase the light — and its duration — by continuing to manipulate the components’ concentration and release rates.
“These plants are not going to be searchlights or floodlights, but we’ve calculated that they can have a level of brightness and duration that will serve many important applications,” Kwak said. “The nearest term applications will be low-intensity indoor lighting, used routinely in architecture. Our numbers are not far off from the required light intensity for these applications.”
As for future streetlights, “the problem of the streetlamp, in the current definition, is a challenge in that a certain level of illumination is required,” she said. However, “if we rethink what we need for transportation lighting, it may be possible. For example, instead of high-intensity illumination spaced relatively far apart, more densely spaced, lower intensity lighting could be substituted.”
Even better, Strano believes they will be able to develop a way to paint or spray the nanoparticles onto plant leaves, which could make it easier to turn trees and other large plants into light sources. “Our target is to perform one treatment when the plant is a seedling or a mature plant, and have it last for the lifetime of the plant,” he said. Recharging would occur naturally via photosynthesis. “Our work very seriously opens up the doorway to streetlamps that are nothing but treated trees, and to indirect lighting around homes.”
Kwak has reassuring news for those with a “black thumb,” who complain they kill every plant they touch. “With our technology, the plants don’t have to be grown or planted in any fashion,” she said. “We infused our nanoparticles to the mature plants that we seeded and watered with no special care or treatment. Also, you can select plants that are relatively easy to take care of, since our light-emitting plants are not limited by species.”
The scientists also know how to turn the lights off. They add nanoparticles carrying a luciferase inhibitor. This means it might be possible to design light-producing plants that shut off in response to an environmental stimulus, such as sunlight.
Glowing plants “are the ultimate in bionic, sustainable illumination, relying on no human infrastructure,” Kwak said. “Plants are already well adapted to the outdoor environment. They self-repair, they already exist in the places where we would like lamps to function, they live and persist through weather events, they access their own water, and they do all of this autonomously.”
Marlene Cimons writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture.