It’s always fun when engineering news coming out of one of the universities makes one think that “Star Trek”-esque technologies are becoming realities, and this is no exception: researchers at Northwestern University have developed a technique for creating entirely new classes of optical materials and devices that could lead to light bending and — wait for it — cloaking devices.

Yep. The interdisciplinary team arranged DNA-modified gold nanoparticles in two and three dimensions to form optically-active “superlattices.” By using numerical simulations and optical spectroscopy techniques, superlattices that absorb specific wavelengths of visible light could then be identified — and individual particles could be programmed to exhibit almost any color across the visible spectrum.

“We now have a new way to precisely control particle architectures over large areas," said chemistry professor Chad A. Mirkin, faculty member at the Weinberg College of Arts and Sciences at Northwestern. "Chemists and physicists will be able to build an almost infinite number of new structures with all sorts of interesting properties. These structures cannot be made by any known technique.”

The researchers’ study, published online in the journal Science, describes a new way to organize nanoparticles in two and three dimensions. The new technique is a creative combination of an old fabrication method — top-down lithography, which is also used to make computer chips — with a programmable self-assembly driven by DNA. Lithography methods were used to drill single-nanoparticle-wide holes in a polymer resist, creating nanoscopic “landing pads” for the nanoparticle components. The landing pads are modified with one sequence of DNA, and the gold nanoparticles are modified with complementary DNA. By alternating nanoparticles with complementary DNA, the researchers were able to build nanoparticle stacks over a large area, with remarkable positional control.

Along with their unusual architectures, the new materials are stimuli-responsive. The DNA strands holding them together change in length when exposed to new environments — which resulted in an accompanying color change, providing extreme tunability of optical properties.

The breakthrough will make it possible to build metamaterials — materials not found in nature — for a range of applications, including medical and environmental sensors. Lattices can be built from any material that can be modified with DNA, with nanoscale precision.

"Our novel metamaterial platform — enabled by precise and extreme control of gold nanoparticle shape, size and spacing — holds significant promise for next-generation optical metamaterials and metasurfaces," said Kory Aydin, a professor in Northwestern’s McCormick School of Engineering.