Just in time for the Halloween, researchers at Carnegie Mellon's Human-Computer Interaction Institute (HCII) have worked out a process for 3D printing strands of hair.

The researchers have created a flexible plastic material, which can be extruded, strand by strand, into synthetic hairs. The hair can be cropped, braided or curled with the help of a little hot air.

The researcher created hair for the head of a troll doll, a beard for a wizard and a tail for a horse. Along with strands of synthetic hair, the researchers were also able to use the technique to make bristles for tooth and hair brushes.

It takes 20 minutes or so to extrude about 10 square millimeters of the plastic hair. But despite being time consuming, the process is simple enough to be completed at home and without any commercial equipment.

"You just squirt a little bit of material and pull away," said Gierad Laput, a Ph.D. student in Carnegie Mellon's HCII. "It's a very simple idea, really."

The researchers had to make a slight modification to the process in which a $300 fused deposition modelling printer extruded the plastic. Instead of moving the print head up and down, the researchers moved it side to side to get the thin hair-like strands that they were after.

"Though the print head can't move up rapidly, both it and the print bed that holds the work in progress can move rapidly from side to side," says the university. "By applying the molten material and then moving the print head and the bed sideways, they found they could create the hair-like strands they wanted."

While the researchers relied on polylactide (PLA), a common material for 3D printing, using more complex materials could make it possible to create hair with novel properties such as magnetism.

Check out the video below to see what's possible with the additive manufacturing technique for hair and bristles: