Using specialized nanoparticles embedded in plant leaves, MIT engineers have
created a light-emitting plant that can be charged by an LED. After 10
seconds of charging, plants glow brightly for several minutes, and they can
be recharged repeatedly.
These plants can produce light that is 10 times brighter than the first
generation of glowing plants that the research group reported in 2017.
"We wanted to create a light-emitting plant with particles that will absorb
light, store some of it, and emit it gradually," says Michael Strano, the
Carbon P. Dubbs Professor of Chemical Engineering at MIT and the senior
author of the new study. "This is a big step toward plant-based lighting."
"Creating ambient light with the renewable chemical energy of living plants
is a bold idea," says Sheila Kennedy, a professor of architecture at MIT and
an author of the paper who has worked with Strano's group on plant-based
lighting. "It represents a fundamental shift in how we think about living
plants and electrical energy for lighting."
The particles can also boost the light production of any other type of
light-emitting plant, including those Strano's lab originally developed.
Those plants use nanoparticles containing the enzyme luciferase, which is
found in fireflies, to produce light. The ability to mix and match
functional nanoparticles inserted into a living plant to produce new
functional properties is an example of the emerging field of "plant
nanobionics."
Pavlo Gordiichuk, a former MIT postdoc, is the lead author of the new paper,
which appears in Science Advances.
Light capacitor
Strano's lab has been working for several years in the new field of plant
nanobionics, which aims to give plants novel features by embedding them with
different types of nanoparticles. Their first generation of light-emitting
plants contained nanoparticles that carry luciferase and luciferin, which
work together to give fireflies their glow. Using these particles, the
researchers generated watercress plants that could emit dim light, about
one-thousandth the amount needed to read by, for a few hours.
In the new study, Strano and his colleagues wanted to create components that
could extend the duration of the light and make it brighter. They came up
with the idea of using a capacitor, which is a part of an electrical circuit
that can store electricity and release it when needed. In the case of
glowing plants, a light capacitor can be used to store light in the form of
photons, then gradually release it over time.
To create their "light capacitor," the researchers decided to use a type of
material known as a phosphor. These materials can absorb either visible or
ultraviolet light and then slowly release it as a phosphorescent glow. The
researchers used a compound called strontium aluminate, which can be formed
into nanoparticles, as their phosphor. Before embedding them in plants, the
researchers coated the particles in silica, which protects the plant from
damage.
The particles, which are several hundred nanometers in diameter, can be
infused into the plants through the stomata—small pores located on the
surfaces of leaves. The particles accumulate in a spongy layer called the
mesophyll, where they form a thin film. A major conclusion of the new study
is that the mesophyll of a living plant can be made to display these
photonic particles without hurting the plant or sacrificing lighting
properties, the researchers say.
This film can absorb photons either from sunlight or an LED. 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, as the team demonstrated during an experimental
exhibition at the Smithsonian Institute of Design in 2019.
"We need to have an intense light, delivered as one pulse for a few seconds,
and that can charge it," Gordiichuk says. "We also showed that we can use
big lenses, such as a Fresnel lens, to transfer our amplified light a
distance more than one meter. This is a good step toward creating lighting
at a scale that people could use."
"The Plant Properties exhibition at the Smithsonian demonstrated a future
vision where lighting infrastructure from living plants is an integral part
of the spaces where people work and live," Kennedy says. "If living plants
could be the starting point of advanced technology, plants might replace our
current unsustainable urban electrical lighting grid for the mutual benefit
of all plant-dependent species—including people."
Large-scale illumination
The MIT researchers found that the "light capacitor" approach can work in
many different plant species, including basil, watercress, and tobacco, the
researchers found. 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. Once the experiments were over, the researchers were able to
extract about 60 percent of the phosphors from plants and reuse them in
another plant.
Researchers in Strano's lab are now working on combining the phosphor light
capacitor particles with the luciferase nanoparticles that they used in
their 2017 study, in hopes that combining the two technologies will produce
plants that can produce even brighter light, for longer periods of time.
Reference:
Pavlo Gordiichuk et al, Augmenting the living plant mesophyll into a
photonic capacitor, Science Advances (2021).
DOI: 10.1126/sciadv.abe9733
Tags:
Nanotechnology