Imagine a sea of glowing blue lights pulsing to the beat of the music. But instead of glow sticks filled with toxic chemicals, the luminescence comes from living algae, shimmering on demand.
In a new study published May 6 in Science Advances, researchers at the University of Colorado Boulder and collaborators unveil a new technology that could make it possible. They've successfully turned on the "light switch" in algae and kept them lit up using simple chemical solutions. The finding opens the door for future technologies such as autonomous robots that can operate in dark environments and living sensors for water quality.
"This project was a moonshot idea," said Wil Srubar , professor in the Department of Civil, Environmental and Architectural Engineering. "I was curious if we could create a world in which we don't use electricity but rather use biology to produce light. This discovery really paves the way for engineering other living light materials and devices."
In the natural world, a wide range of animals, from fireflies to anglerfish and even certain mushrooms, produce their own light, a phenomenon known as bioluminescence. In the deep ocean, as much as 90% of creatures may be able to glow and glitter through chemical reactions inside their cells.
Pyrocystis lunula, a type of bioluminescent algae, is one of the organisms that emit an icy blue glow sometimes seen in ocean waves. Subsisting only on seawater, sunlight and carbon dioxide (CO2), these photosynthetic organisms flash when they are agitated by crashing tides or passing boats, for example.
But those flashes last only milliseconds. Srubar and his team wondered if they could keep the lights on with chemistry instead. Previous research has suggested that exposure to different chemical compounds could activate P. lunula's bioluminescent reaction. So the team exposed the algae to an acidic solution with a pH of 4, similar to that of tomato juice, and a basic solution with a pH of 10, comparable to mild soap.
They found that both environments could trigger light production in P. lunula. In the acidic condition, the algae could stay aglow for as long as 25 minutes, with light appearing bright and concentrated. In the basic condition, the glow was more diffused and short-lived.
"It was a very exciting moment when we found the right chemical stimulant that allowed the light to stay on for a long time," says Giulia Brachi, the first author and research associate in the Department of Civil, Environmental and Architectural Engineering. "This is the first time we have figured out how to sustain luminescence."
To turn these glowing algae into usable materials, the researchers embedded them into a naturally derived hydrogel, a type of water-based gel material. They then used 3D printing to shape the material into structures and shapes, from a crescent pattern to a CU Buffalo logo.
By exposing the structures to the acidic or basic solution, they prompted the P. lunula inside to emit light, illuminating the entire structure in a blue glow.
Inside these printed structures, the algae remained alive for weeks. The acidic condition worked best, with P. lunula in these 3D printed structures retaining 75% of their brightness even after four weeks.
The findings could have wide applications beyond making eye-catching designs. These living materials could someday help light up autonomous robots for deep-sea or space exploration without the need for batteries.
Next, the team is exploring whether P. lunula may respond to other chemicals. If so, they could also serve as a tool for water quality monitoring and light up when toxins are present.
Beyond their ability to light up spaces, P. lunula also offers an environmental benefit. Because these algae are photosynthetic, they convert carbon dissolved in seawater into energy.
"We're storing carbon while we're producing light, whereas conventionally, we emit carbon to light up spaces," Srubar said.
And yes, future rave scenes could someday glow with light powered by living algae.
