MIT can now 3-D print hair. But unless you’re going for the Andy Warhol look, then this hair isn’t for heads. The plastic filaments can be used as sensors, to move things, and—like animal hair—as insulation. But the hair’s uses aren’t the most impressive thing about it. What’s extraordinary is that it can be printed at all.
Imagine making a modern blockbuster superhero movie and trying to create those amazing special effects one pixel at a time. Is the tip of that blade of grass further away than the tip of the one next to it? Is that particle of an ocean wave all foam, or just almost foam? That’s the problem faced when 3-D printing hair. While a computer could model the hair, no problem, in a similar way to making VFX hair in a movie, it would then have to be translated into pixels that could be printed. And when you’re making hair that’s just 50 microns thick (like human hair), then you need to be super accurate so it all lines up. It would take hours just to make the pixel map, before you even fire up the printer.
The MIT team, led by graduate student Jifei Ou, instead made software that can directly generate hair-like structures and feed them straight into the 3-D printer. It’s like the simulations used by movie visual effects artists, where they specialized software for making water—they just tell it how big a wave should be, and the app does all the work. With hair, the formula is relatively simple, as hairs are pretty much just long strands.
The paper details the many clever uses, apart from making the world’s fanciest nail brush. For instance, you could make a paintbrush with a customized stroke, or Velcro-like bristles that can stick with varying force. You could print insulating hair onto an object to keep warm or cold in or out, and of course you can print all manner of novelty toys, as the accompanying video shows.
The fine control over the shape and size of the hairs lets you make all kinds of neat devices. The team printed a sorting panel with hairs set at particular angles and heights. "As a small vibration source shook the panels, the hairs were able to move coins across the table, sorting them based on the coins’ weight and the vibration frequency," writes MIT News’ Jennifer Chu. The same idea can be used for plain movement, using the vibration of the hairs to make objects skitter across them in a controlled path, or even to make a linear or a rotary motor, powered by vibration.
And hair can be used for yet another task, one it performs in nature—a sensor. Just like our body hairs raise an alert when an insect gets too close, MIT’s hair can be used to sense touch, in this case by putting it on top of a microphone and measuring the sound it makes when objects brush past. This setup is sensitive enough to detect the direction and speed of the movement.
The work is impressive, but more likely to show up in industrial processes than in consumer applications. So, no 3-D printed wigs yet, but when they do inevitably arrive, they will be way more useful than that passive mop that you wear on top of your head right now. Who knows? Maybe prosthetic hair will become a thing one day.
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