Harvard University engineers have come up with a production technique inspired by pop-up books and origami, that allows clones of tiny robots to be mass-produced in sheets.

Pratheev Sreetharan and colleagues at the Harvard Microrobotics Laboratory have been working on bio-inspired robots that are about the same size as a bee, can fly and can work autonomously as a robotic colony.

But actually building the little blighters was a painstaking and error-prone process, as the engineers manually folded, aligned and secured each of the minuscule joints.

"You'd take a very fine tungsten wire and dip it in a little bit of superglue," says Sreetharan in a press release. "Then, with that tiny ball of glue, you'd go in under a microscope like an arthroscopic surgeon and try to stick it in the right place."

With the new method the engineers don't just fabricate the robot, but also produce a surrounding "assembly scaffold" that's attached to the bee-bot by tiny hinges. When the scaffold is lifted by pins, it folds the flat robot's joints and turns it into a 3D

model.

The Harvard Monolithic Bee (or Mobee), for example, turns from a flat shape into a 2.4-millimetre-tall robot in just one movement – just like a pop-up book. The folding process takes less than a second.

The whole structure is made like a printed circuit board. 18 layers of different materials (carbon fiber, a plastic film called Kapton, titanium, brass, ceramic, and

adhesive sheets) are laminated together in a thin, laser-cut design.

Then the pins pop-up from the bottom to fold everything into place. The whole shebang is dunked in a liquid metal solder to bond tiny brass together, which lock the robot's joints in place.

Finally, the scaffold is removed by laser cutting, releasing the tiny bee-bot.

The pop-up process will allow microbots to be rapidly fabricated, assembled and deployed – and because the robots are so small, you could print dozens on a single sheet.

While the process was designed to produce micro-air vehicles, the same technique could be used for pretty much any 3D object that needs a number of material layers, integrated electronics and lots of tiny hinges. Any electromechanical devices that has parts on the

scale of micrometers to centimeters could benefit.

–Mark Brown