U.S. Army Research Laboratory

A team of researchers figured out how to get 3 mm microstructures to fold in response to low-intensity laser light, but now their focus is even smaller. U.S. Army Research Laboratory

Lasers could help fire weapons or set off explosive warheads for the U.S. Army in the near future. That possibility comes from a lab demonstration of how a simple, handheld laser can fold tiny metallic structures in a style that mimics Japanese origami.

The demonstration suggests that similar systems could produce tiny grippers and switches that would act as mechanical components in small devices. The components could be used to detonate explosive or propellant material, attach identification transponder tags to clothing, or even enable a new generation of extremely tiny robots or electronic devices.

"We are enabling true microsystems, where all of the energy and functions are self-contained in a millimeter- or smaller-sized package," said Christopher Morris, a researcher focused on micro-materials and devices at the U.S. Army Research Laboratory.

Army researchers became interested in the concept after seeing work that Johns Hopkins University had done in making micro devices for performing surgery. But the Army took the method a step farther by creating millimeter-sized structures that could be triggered by low-power lasers or even LED lighting.

The tiny structures act as mechanical hinges capable of folding along certain "stress" lines built into the layered metal. When a laser shines onto the structure, its energy softens a polymer "trigger" that normally prevents the hinges from folding.

A handheld laser operating on "eye-safe" levels could trigger the folding action from up to 3 feet away during testing detailed in the journal Applied Physics Letters and highlighted in the journal Nature Photonics.

Folding time ranged from 67 milliseconds to 21 seconds, depending on the wavelength and intensity of laser light, but larger structures required several minutes. The Army Research Laboratory takes about 20 hours to make a sheet of the millimeter-sized folding structures.

"Our hope is that new uses will spur from this basic scientific exploration of novel fabrication and self- assembly of materials, and will help future soldiers in ways they may not even see," Morris said.