World's fastest stretchy circuits created

Engineers have created stretchable integrated circuits, with a unique structure inspired by twisted-pair telephone cables, which are being touted as the fastest circuits of their kind in existence.

Created by a team of University of Wisconsin-Madison engineers, the circuits could help manufacturers seeking to expand the capabilities and applications of wearable electronics — including those with biomedical applications — particularly as they strive to develop devices that take advantage of a new generation of wireless broadband technologies referred to as 5G.

With wavelength sizes between a millimetre and a metre, microwave radio frequencies are electromagnetic waves that use frequencies in the 0.3 gigahertz to 300 gigahertz range. That falls directly in the 5G range.

In mobile communications, the wide microwave radio frequencies of 5G networks will accommodate a growing number of mobile phone users and notable increases in data speeds and coverage areas.

In an intensive care unit, epidermal electronic systems (electronics that adhere to the skin like temporary tattoos) could allow healthcare staff to monitor patients remotely and wirelessly, increasing patient comfort by decreasing the customary tangle of cables and wires.

What makes the new, stretchable integrated circuits so powerful is their unique structure, inspired by twisted-pair telephone cables. They contain, essentially, two ultra-tiny intertwining power transmission lines in repeating S-curves.

This serpentine shape — formed in two layers with segmented metal blocks, like a 3D puzzle — gives the transmission lines the ability to stretch without affecting their performance. It also helps shield the lines from outside interference and, at the same time, confine the electromagnetic waves flowing through them, almost completely eliminating current loss. Currently, the researchers’ stretchable integrated circuits can operate at radiofrequency levels up to 40 gigahertz.

And, unlike other stretchable transmission lines, whose widths can approach 640 micrometres (or 0.64 mm), the researchers’ new stretchable integrated circuits are just 25 micrometres (or 0.025 mm) thick. That’s tiny enough to be highly effective in epidermal electronic systems, among many other applications.

Led by Zhenqiang ‘Jack’ Ma, the Lynn H. Matthias Professor in Engineering and Vilas Distinguished Achievement Professor in electrical and computer engineering at UW–Madison, the researchers published details of these powerful, highly efficient integrated circuits in the journal Advanced Functional Materials.

Ma’s group has been developing what are known as transistor active devices for the past decade. This latest advance marries the researchers’ expertise in both high-frequency and flexible electronics.

“We’ve found a way to integrate high-frequency active transistors into a useful circuit that can be wireless,” said Ma, whose work was supported by the Air Force Office of Scientific Research.

“This is a platform. This opens the door to lots of new capabilities.”