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Making It

MIT Is Building Touchable Interfaces Out Of Soft, Synthetic Hair

Cilia are found everywhere in nature, including inside our own bodies. Now, MIT has figured out a way to 3-D print them.

MIT Is Building Touchable Interfaces Out Of Soft, Synthetic Hair

Cilia are an amazing biological phenomenon. These super-sensitive microscopic hairs are all over (and inside) us humans, along with many other organisms. They help us hear, eat, and breathe, and they even help us conceive.

In a way, cilia and other types of hair evolved to serve as a natural interface. Hair, after all, "interfaces between the living organism and its environment," writes Jifei Ou, a PhD candidate at MIT’s Tangible Media Lab and the creator of Cilllia, a project based on the biological concept.

Cilllia could give us a better physical solution for interacting with technology—by mimicking the way our natural, hair-like cilia detect vibrations.

Hair: The Ultimate Challenge For 3-D Printing

Unsurprisingly, engineers have been trying to replicate these powerful little hair-like structures for years. In 2010, scientists at the University of Southern Mississippi reported that they had created the first synthetic cilia that could sense chemicals and heat. Others have shown how tiny cilia could be used in robotics, drug delivery, and more.

The most obvious way to fabricate cilia-like hair outside of a science lab is through rapid prototyping technology. But 3-D printing hair is a major, long-standing challenge, not only because most printers aren't precise enough to print at that level of detail, but because 3-D modeling software isn't really designed for it, either. Creating a CAD model of thousands of fine hairs, each with its own surface geometry, produces a huge, unwieldy model. Neither our modeling tools, or our printers, are set up to handle the unique geometry of hair.

Ou and his collaborators at MIT think they’ve found a solution, by building their own software tool for modeling hair in an entirely new way. Rather than describing the surface geometry of each hair, their program represents a single hair as a much simpler tower of individual pixels. Instead of a complex 3-D model of the surface of every single piece of hair, the software lets you create strands of simple pixels that you can customize based on thickness, height, and even shape.

That took care of the modeling problem. To fabricate it, the researchers turned to Autodesk's high-resolution Ember printer (they also used a FormLabs printer for a few of the prototypes). They were able to print an incredible array of hair types and shapes, like paintbrushes with unusual profiles and curved surfaces covered in dense mats of cilia the width of an average human hair. On a single two-inch-wide piece of material, they printed 20,000 individual hairs. For reference, your head probably has about 100,000 follicles in all.

But Ou and his co-authors aren’t just demonstrating a new way to 3-D print hair—they’re demonstrating how biomimicry could transform interaction design.

Biomimicry For Interfaces

Caterpillars, fruit flies, and many other organisms use cilia to translate sound waves or vibrations into information about the world around them. Our own ears use cilia the same way: In your inner ear, stereocilia hairs take the vibrations of sound waves and turn them into electrical stimulation in your brain.

In other words, these hairs turn mechanical movement into electrical signals—which is exactly what Cilllia aims to do artificially, by acting as a super-accurate sensor that can recognize a human gesture and turn it into an electrical signal to be processed by a computer or processor. "When being swiped, a hair array generates an almost inaudible sound by its vibration," the project team explains. "One can therefore capture and analyze the sound to reveal the direction and velocity of swiping."

To demonstrate, they printed a mat of dense hairs and glued a simple piezo sensor—which recognizes vibrations—to the underside of the mat. Over the course of several prototypes, they developed a way to accurately recognize different human finger swipes with the help of a machine-learning algorithm. An interface that’s covered in this soft hair, or fur, would be able to interpret how a human touched it. "We can now print a furry animal that senses petting without adding any electronics or obtrusive geometry on the surface of the figure," Ou writes. Just like whiskers, which can help a cat navigate in the dark by sending signals to the brain, a toy covered in these cilia could communicate with an internal processor about how it’s being handled.

But over email, Ou says there’s a much more novel use for this tech. In one prototype, the team printed a mat of two different types of hair, each with its own stiffness and shape—which meant that each of the two hair shapes would vibrate at a different sound frequency. Just by creating specific vibration frequencies below it, they were able to move an object placed on the mat in specific patterns, and even sort objects of different weights. Ou thinks this tech could be used to create inexpensive robotic technology. "This might be useful for sorting tiny pieces in a factory, or even sorting pills at large quantity," he speculates.

The team presented their concept at CHI 2016—the major human-computer interaction conference that wrapped up last week—but they plan to continue working on the project. Next, they want to test how well Cilllia can sense more gestures, like multitouch and force, and to understand how different hair shapes could be used to sort objects the way Ou envisions.

Will their novel hair-modeling technique ever be released to the public? Ou hopes to open it to developers working on CAD software soon, so that one day his model could be a standard feature in 3-D modeling programs. In the meantime, read more here.

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