MIT 'breakthrough' 3D printing technique can print out solids and liquids at the same time

MIT's computer scientists have made a breakthrough that enables commercial 3D printers to be adapted to print out solids and liquids at the same time, which could make it possible for machines to one day manufacture robots in their entirety – so they roll out ready for use.

Researchers from MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) have developed a new 3D printing technique known as "Printable Hydraulics", which takes photopolymer 3D printers and adds the ability for liquids to be neatly printed at the same time as solids and stored within the solid material as the object is printed.

"We have a 3D printer that can lay out either solids or liquids, and then we have an algorithm that decides when the printer should put down a water droplet or solid droplet. This allows us to create objects that were not possible to create before," CSAIL director Daniela Rus told IBTimes UK.

"This allows us to 3D print hydraulic mechanisms and incorporate them into the robot. The reason the liquids stay liquid is because they are enclosed in a mechanism of pipes."

3D printing hydraulic mechanisms

Today's consumer 3D printers use Fused Deposition Modelling (FDM) technology to build objects layer by layer from the bottom up, heating thermoplastic filament and extruding the melted material from a nozzle, which then hardens on the print bed.

In contrast, Stereolithography, one of the oldest 3D printing technologies that is still used in commercial 3D printers, has more in common with desktop inkjet printers as it uses droplets of curable liquid plastic. An ultraviolet laser is used to harden the polymer, forming solid objects and creating incredibly smooth, detailed models in a wide variety of colours within the same model.

"When the parts are being printed, they're being printed layer by layer, in very thin layers. At those kinds of scales, at the height of the layers, the size of the droplets we deposit allows materials that are solids and liquids to sit next to each other on that layer, because of the surface tension of these droplets," CSAIL post-doctoral associate Robert MacCurdy, who co-wrote the paper, told IBTimes UK.

"The materials that are solid are eradiated by ultraviolet light to solidify them, but not the droplets. This lets us embed very detailed hydraulic channels to actuate robotic and electromechanical parts. The fact we can embed these materials, which stay as part of the finished part, and we do not need to add or remove anything, that really sets this apart from other processes."

The MIT researchers used a typical commercial photopolymer 3D printer. Over the course of a year, they figured out how to add a liquid made from alcohol to the printer to make combined printing possible.

Consumers could one day print out robots at home

At the moment, it is extremely time-consuming and complex to assemble robots, and robots are not yet intelligent enough to be used to build other robots. The researchers envision a future where single-use, disposable robots can be printed easily at home.

"The ultimate goal of this work is to be able to tell a 3D printer to print out a robot to fulfil a specific function, such as a robot to clean your floor, crawl through rubble or pick up and shelve books," said Rus.

"So you tell the printer what you want, and you would like the printer to figure out and fabricate the design, and integrate the computational programming, so the robot could walk itself out of the printer."

The paper, entitled Printable Hydraulics: A Method for Fabricating Robots by 3D Co-Printing Solids and Liquids is published on Cornell University Library's open source database. It was also accepted to be presented at the 2016 IEEE International Conference on Robotics and Automation (ICRA) in Stockholm, Sweden from 16 to 21 May.