In this age of smartphones and tablet computers, touch-sensitive surfaces are everywhere. They're also brittle, as people with cracked phone screens everywhere can attest.

Covering a robot—or an airplane or a bridge—with sensors will require a technology that is both flexible and cost-effective to manufacture in bulk. A team of researchers at MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) thinks that 3-D printing could be the answer.

In an attempt to demonstrate the feasibility of flexible, printable electronics that combine sensors and processing circuitry and can act on their environments, the researchers have designed and built a device that responds to mechanical stresses by changing the color of a spot on its surface.

The device was inspired by the golden tortoise beetle, or "goldbug," an insect whose exterior usually appears golden but turns reddish orange if the insect is poked or prodded—that is, mechanically stressed.

 

"In nature, networks of sensors and interconnects are called sensorimotor pathways," said Subramanian Sundaram, an MIT graduate student in electrical engineering and computer science (EECS), who led the project. "We were trying to see whether we could replicate sensorimotor pathways inside a 3-D-printed object. So we considered the simplest organism we could find."

The researchers present their new design in the latest issue of the journal Advanced Materials Technologies. Sundaram is the first author on the paper, and the senior authors are Sundaram's advisor, Wojciech Matusik, an associate professor of EECS; and Marc Baldo, a professor of EECS and director of the Research Laboratory of Electronics. Joining them on the paper are Pitchaya Sitthi-Amorn, a former postdoc in Matusik's lab; Ziwen Jiang, an undergraduate EECS student; and David Kim, a technical assistant in Matusik's Computational Fabrication Group.