how billions of microdrones will be made...,

Harvard | A new technique inspired by elegant pop-up books and origami will soon allow clones of robotic insects to be mass-produced by the sheet.

Devised by engineers at Harvard, the ingenious layering and folding process enables the rapid fabrication of not just microrobots, but a broad range of electromechanical devices.

In prototypes, 18 layers of carbon fiber, Kapton (a plastic film), titanium, brass, ceramic, and adhesive sheets have been laminated together in a complex, laser-cut design. The structure incorporates flexible hinges that allow the three-dimensional product—just 2.4 millimeters tall—to assemble in one movement, like a pop-up book.

The entire product is approximately the size of a U.S. quarter, and dozens of these microrobots could be fabricated in parallel on a single sheet.

"This takes what is a craft, an artisanal process, and transforms it for automated mass production," says Pratheev Sreetharan (A.B. '06, S.M. '10), who co-developed the technique with J. Peter Whitney. Both are doctoral candidates at the Harvard School of Engineering and Applied Sciences (SEAS).

Sreetharan, Whitney, and their colleagues in the Harvard Microrobotics Laboratory at SEAS have been working for years to build bio-inspired, bee-sized robots that can fly and behave autonomously as a colony. Appropriate materials, hardware, control systems, and fabrication techniques did not exist prior to the RoboBees project, so each must be invented, developed, and integrated by a diverse team of researchers.

Less than a year ago, the group was using a painstaking and error-prone method to fold, align, and secure each of the minuscule parts and joints.

"You'd take a very fine tungsten wire and dip it in a little bit of superglue," explains Sreetharan. "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."

"Until recently, the manual assembly process was the state of the art in this field," Sreetharan adds.

By the numbers

• Folding joints: 22
• Assembly scaffold folding joints: 115
• Total device folding joints: 137
• Number of brass pads for "glue" points: 52
• Total number of "glue" points: 24
• Mass: 90 mg
• By mass, one U.S. quarter = 63 Harvard Monolithic Bees
  

The same result can now be achieved—without human error—through locking mechanisms and dip soldering. The new process also enables the use of cured carbon fiber, which is rigid and easy to align, rather than uncured carbon fiber, which Sreetharan compares to "wet tissue paper."

"Our new techniques allow us to use any material including polymers, metals, ceramics, and composites," says principal investigator Rob Wood, an Associate Professor of Electrical Engineering at SEAS and a Core Faculty Member at the Wyss Institute for Biologically Inspired Engineering at Harvard.

"The ability to incorporate any type and number of material layers, along with integrated electronics, means that we can generate full systems in any three-dimensional shape," Wood says. "We've also demonstrated that we can create self-assembling devices by including pre-stressed materials."