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A robot made of Lego can quickly perform an important step for creating machines made of DNA.

“This started as a final project in an undergraduate lab course,” says at Arizona State University, who tasked his class with building tools using “frugal science”.

The robot that one group of students built has proved particularly useful and resembles a single arm topped with a holder for cylindrical tubes. It performs a procedure to mix the liquid contents of the tubes, first tilting the tubes from vertical to horizontal, then rapidly spinning them around. This creates a single liquid with a density that uniformly decreases from the bottom to the top.

The robot’s parts, including gears, connecting blocks and two motors, all come from Lego kits. The only exception is the tube holder that the researchers had to 3D print. The robot’s design is a smaller and faster version of more traditional “gradient mixers”.

After being mixed by the Lego robot, the liquid can be used for purifying tiny structures made of DNA molecules that researchers like Hariadi want to use as tiny machines. These machines could both carry out tasks inside of cells and shed new light on how naturally occurring molecular machines, like proteins, work.

Many conventional methods for creating density gradients require hard-to-use and expensive machines. The Lego robot created the necessary density gradient in only 1 minute, which speeds up the purification overall.

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at the University of Edinburgh in the UK says the robot could make the purification process both cheaper and quicker.

The purification procedure includes devices other than the Lego robot, so the robot itself may not be of use to other laboratories that don’t already have this remaining equipment, says Hariadi . However, because it only cost about $350 to make it out of Lego – store-bought devices range from $500 and $5000  – this is a convenient and accessible way to prototype devices that can improve existing lab routines, he says.