The rapid advancement of 3-D printing has lead to many scientists hailing the emerging technology as one that will transform our lives in amazing ways. Now, a new step will likely fuel this fire, as researchers from MIT's Computer Science and Artificial Intelligence Laboratory have created 3-D printed robots made from a combination of liquids and solids.

Although 3-D printing has never before been conducted with liquids, the new experiment uses the combination of liquids and solids to allow for the faster creation of complex designs, decreasing the time and money needed to make robots as a result.

"Printable robots like these can be quickly, cheaply fabricated, with fewer electronic components than traditional robots," said Robert MacCurdy, an MIT postdoc and co-author of the study.

Using this unique "printable hydraulics" process, the team used an inkjet printer to stack up layers of material half the width of a human hair. They conducted this process one drop at a time, using high-intensity ultraviolent light to solidify the material that is to be solid after each layer and leaving the liquids as they are.

The new findings can help scientists create cheaper robots that will make remote exploration more affordable and open up many doors that were previously closed in the robot industry.

"The ability of printing solids and liquids at the same time will enable us to create a whole different class of active mechanisms," said Daniela Rus, the MIT professor who oversaw the project. "The idea of reducing or simplifying the amount of manual assembly that's required to create robots is really critical for getting broader adoption of robots, and making them more accessible."

"It makes a big difference in what kind of machines you can make," she added. "If you can make complex robots really fast - print them like you print a piece of paper - you can imagine not having to worry so much about whether you lost your robot."

The team used their new method to create tiny robots that possess hydraulic bellows filled with fluid. They then added a battery, sensors and computer them in order to let them walk independently.

Although Rus and her team plans on commercializing the technology eventually, they first want to expand and improve on the current robot design, which took 22 hours to create and cost more than $100,000.

The findings were accepted for this summer's IEEE International Conference on Robotics and Automation (ICRA).