Engineers make nanoscale muscles powered by DNA

The base pairs found in DNA are key to its ability to store protein-coding information, but they also give the molecule useful structural properties. Getting two complementary strands of DNA to zip up into a double helix can serve as the basis of intricate physical mechanisms that can push and pull molecular-scale devices. 

Engineers at the University of Pennsylvania have developed nanoscale "muscles" that work on this principle. By carefully incorporating strands of custom DNA into different layers of flexible films, they can force those films to bend, curl and even flip over by introducing the right DNA cue. They could also reverse these changes by way of different DNA cues.

One day, the flexing of these muscles could be used in diagnostic devices, capable of signaling changes in gene expression from within cells.

The study was led John C. Crocker and Daeyeon Lee, professors of Chemical and Biomolecular Engineering in Penn's School of Engineering and Applied Science.

The nanoscale muscles in the study are comprised of gold nanoparticles, which are connected to one another by single-stranded DNA. The researchers built up the films layer-by-layer, introducing different sets of DNA-linked nanoparticles at different depths. Each set of nanoparticles contained links with different sequences.

"The way the actuation works," Crocker said, "is that we add single-stranded DNA that is complementary to a portion of the bridges between the particles. When that DNA diffuses in, it turns just those bridges into double-stranded DNA helices."