Necrobotics is a field of engineering that builds robots out of a mix of synthetic materials and animal body parts. It has produced micro-grippers with pneumatically operated legs taken from dead spiders and walking robots based on deceased cockroaches. “These necrobotics papers inspired us to build something different,” said Changhong Cao, a mechanical engineering professor at the McGill University in Montreal, Canada.
Cao’s team didn’t go for a robot—instead, it adapted a female mosquito proboscis to work as a nozzle in a super-precise 3D printer. And it worked surprisingly well.
Fangs and stings
To find the right nozzle for their 3D necroprinting system, Cao’s team began with a broad survey of natural micro-dispensing tips. The researchers examined stingers of bees, wasps, and scorpions; the fangs of venomous snakes; and the claws of centipedes. All of those evolved to deliver a fluid to the target, which is roughly what a 3D printer’s nozzle does. But they all had issues. “Some were too curved and curved for high-precision 3D printing,” Cao explained. “Also, they were optimized for delivering pulses of venom, not for a steady, continuous flow, which is what you need for printing.”
Continuous flow optimization, on the other hand, was a feature of some proboscises, the tube-like mouth parts some insects use to draw blood from their prey. These, the scientists found, were usually very thin and robust to enable piercing through thick skin and straight to make feeding easier. That’s why the final choice of nozzle donors came down to a decision between tsetse flies, sandflies, aphids, bed bugs, assassin bugs, and female mosquitoes. The mosquitoes ended up winning the competition.
The researchers found the female mosquito proboscis has an inner diameter measuring 20–30 microns, far smaller than most stingers or fangs, and it had a straight, long structure, making it easy to align as a nozzle. “It’s also stiff and strong, which allows it to withstand printing pressures,” Cao said. The only problem left was building a 3D printer around it.
Necroprinting
Cao and his colleagues called the device they created a “3D necroprinter.” It was based on an Aerotech precision motion stage, a mechanical positioning system that can move the printing head with ten-nanometer resolution over a stable, vibration-isolated platform. The extrusion mechanism itself was simple: a syringe-based direct ink writing system that pushed their printing material through a small plastic tip.