April showers bring May flowers. But in this case, the blossoms are too small for even a bumblebee to see.
Engineers at Harvard University have figured out a way to make microscopic sculptures of roses, tulips and violets, each smaller than a strand of hair.
To get a sense of just how small these flower sculptures are, grab a penny and flip it on its back. Right in the middle of the Lincoln Memorial, you'll see a faint impression of Abraham Lincoln. These roses would make a perfect corsage for the president's jacket lapel.
Growing the gardens is similar to making crystals with a Magic Rock kit.
The flowers sprout up spontaneously when a glass plate is dipped into a beaker filled with silicon and minerals (specifically, barium chloride). Then Wim Noorduin at Harvard coaxes the salts to spiral and swirl into smooth, curvaceous shapes, like vases, leaves and petals.
He sculpts the stems and blossoms by slightly tweaking the environment in which the crystals grow. Lowering the temperature makes the petals thicker. Bursts of carbon dioxide send ripples through the leaves and blossoms.
The result is thousands of microviolets carpeting the surface of the glass plate.
"Every flower has a unique shape," Noorduin says. "It is very sensitive. If I just walk by the beaker in the lab, it changes the growth of these structures."
Noorduin has even seeded the crystals on the back of a penny, creating a garden of nanotulips on the steps of the Lincoln Memorial.
"It's a completely new world that you can make," he says. "And these flowers last — they don't go bad. Even after years, you can still see them."
Noorduin can add color to the flowers by mixing dyes into the solutions. But he still has to colorize the images with Photoshop because the electron microscope only takes photos in black and white. He tries to match the colors in Photoshop with those in the actual flowers, though. "Like the rose structure with the green stem," he says, "these are the real colors of the sculpture."
He and his colleagues describe the microgardening technique in the current issue of the journal Science.
So far, they've focused only on making aesthetically pleasing structures, but Noorduin says the technique could be used to make any complex shape or architecture you want — at an incredibly small size.
"It's a little bit similar to 3-D printing," he says. "Right now there are more options and varieties of shapes available in 3-D printing because it's 30 years old. We're just starting."
Eventually, he and the team at Harvard hope to use the method to create microelectronics, medical sensors and new materials for optics. "At this [size] scale, really interesting things happen with light," he says.
"When you look around you, nature can make very complex structures almost effortlessly," he adds. "Now we've demonstrated that we can make similar shapes by really doing very little, too."