Manu Prakash’s lab at Stanford is all about looking in the smallest places for innovative ideas. Prakash and his team have discovered how certain insects walk on water and how small traces of chemicals can make water droplets move like living creatures. Prakash then tries to recreate these beautiful tiny movements of nature in tools, like postcard-size tests for malaria or a "lab on a chip" device for medical testing powered by a hand crank.
And it all starts off with observations of the small and beautiful mechanics of the natural world.
Here’s a great example. Prakash’s lab has captured how starfish larvae, smaller than a millimeter long, eat: They flap tiny hairlike structures to create several vortexes around their bodies, which push algae into their guts.
The lab’s time lapse of the process is simply beautiful. (The white lines you see are trails of tiny plastic beads floating in the water around the starfish, which are used as markers to track the motion of the water.)
The GIF is adapted from a video Prakash and his colleagues published in the Gallery of Fluid Motion, a site that hosts some of the most beautiful and mystifying visualizations of fluid dynamics from labs across the world. This one from Prakash and colleagues, posted below, was one of the award winning videos in the gallery’s annual contest. (See more of the Gallery of Fluid Motion videos here. The one on paint drying is particularly mesmerizing. Really.)
The video isn’t just pretty — it also demonstrates a key bit of the starfish’s evolution.
“Our video shows how millions of years of evolution have allowed the larva to master fluid physics in order to solve the unique dilemma of feeding at the microscale,” the team writes on the Gallery of Fluid Motion website. “But this innovation comes with a price: the vortexes decrease the animal's swimming speed, and thus its ability to change locations and escape predators. By studying how physical forces shape the adaptation of simple animals, we hope to uncover the subtle manner in which physics shapes evolution.”
So how do the starfish generate these vortexes? They beat the hairlike cilia on either side of their arms in opposite directions, which spins the water around.
The larvae can actually control how many vortexes they form, which allows them to swim away when they need to stop feeding or evade a predator.
It’s possible this insight into starfish locomotion could one day aid water filtration systems or be implemented in robotics, Prakash and his co-authors write in a paper that has yet to be printed in a scientific journal. But for now it’s just an observation, which is a key first step for scientific discovery.
“I think observations are the most important thing, personally for me,” Prakash told me in September, after he was awarded a MacArthur “genius” grant. “Almost all of the work starts with an observation. ... In every level deeper you look, you realize there is more to be and more to know.”
