Creating Elastic Conductors

Photo: Buckled nanotubes

“We’re optimistic that this new approach could lead to large-scale production of stretchable conductors, which would then expedite research and development of elastic electronic devices,” says Doctor Yong Zhu, an assistant professor of mechanical and aerospace engineering at NC State, and lead author of a paper describing the new technique.

The buckled nanotubes look like squiggly lines on a flat surface. Stretchable electronic devices would be both more resilient and able to conform to various shapes. Potential applications include devices that can be incorporated into clothing, implantable medical devices, and sensors that can be stretched over unmanned aerial vehicles.

To develop these stretchable electronics, one needs to create conductors that are elastic and will reliably transmit electric signals regardless of whether they are being stretched.

One way of making conductive materials more elastic is to “buckle” them. Zhu’s new method buckles carbon nanotubes on the plane of the substrate. Think of the nanotubes as forming squiggly lines on a piece of paper, rather than an accordion shape that zigs up and down with only the bottom parts touching the sheet of paper. Zhu’s team used carbon nanotubes because they are sturdy, stable, excellent conductors and can be aligned into ribbons.

The new process begins by placing aligned carbon nanotubes on an elastic substrate using a transfer printing process. The substrate is then stretched, which separates the nanotubes while maintaining their parallel alignment.

Strikingly, when the substrate is relaxed, the nanotubes do not return to their original positions. Instead, the nanotubes buckle – creating what looks like a collection of parallel squiggly lines on a flat surface.

The carbon nanotubes are now elastic – they can be stretched – but they have retained their electrical properties.

The key benefit of this new method is that it will make manufacturing of elastic conductors significantly more efficient, because the carbon nanotubes can be applied before the substrate is stretched. This is compatible with existing manufacturing processes. “For example, roll-to-roll printing techniques could be adapted to take advantage of our new method,” Zhu says.

COMPAMED.de; Source: North Carolina State University