Trees planted along busy city streets can provide shade by day, but could they also provide light at night? Researchers in Denmark want to isolate the genes that cause ocean algae to glow and insert them into trees, creating natural streetlights.

“We could try to change some of that lighting from conventional, electricity-consuming lights to a more natural way of creating light,” Kristian Ejlsted, CEO of Allumen, a startup based near Copenhagen, told Fast Company.

Ejlsted’s research into creating bioluminescent trees, which began when he was a student at the Technical University of Denmark, is in the early stages. But he believes the payoff could be a huge electricity savings for cities where street lighting consumes much of the energy costs.

“In Denmark, almost all streetlights are now being replaced by LED lights,” Ejlsted said. “That’s a huge deal right now, and it’s going to save a lot of energy. But the fact is that they’re still using electricity.” The advantage of switching to a biological system, he said, is that plants and algae need only CO₂, sunlight, and water.

Along with the technical challenges involved in getting a gene found in algae to produce bioluminescence in a tree, the project’s proposed use of genetically engineered trees raises ethical and environmental questions.

“What happens to the animals and plants that surround them, cross-fertilize with them, or feed on them?” asked Dimitri Deheyn, a researcher at Scripps Institution of Oceanography, according to Fast Company.

If successful, the glowing trees would have an advantage even over lights powered by renewable energy sources, said Ejlsted. He pointed out that algae are naturally very efficient at capturing sunlight: “We can’t really recreate that yet in solar panels.”

Flight of the RoboFly

Drones keep getting smaller and smaller. You can buy one today that fits in the palm of your hand. Engineers have even created insect-sized drones that fly using flapping wings instead of propellers. But these devices must still be tethered to an external power source because current batteries are too heavy for them to carry.

Now engineers at the University of Washington have created the first wireless flying insect robot. Powered by an invisible external laser, the “RoboFly”—slightly heavier than a toothpick—converts the laser energy into electricity using a tiny photovoltaic cell.

RoboFly is currently limited to operating within a direct line of sight of the laser beam, which has a range of about 7 feet. Future versions might be battery-powered or harvest energy from radio signals. The research team believes swarms of insect-size drones could be useful for tasks such as surveying crop growth on large farms or detecting gas leaks.

“I’d really like to make one that finds methane leaks,” said Sawyer Fuller, an assistant professor in the UW Department of Mechanical Engineering, according to UW News. “You could buy a suitcase full of them, open it up, and they would fly around your building looking for plumes of gas coming out of leaky pipes.” —M.C.