Cunjiang Yu develops the first rubber electronics that offer CMOS functionality

In a new paper published in Science Advances, Cunjiang Yu and his research team, including several of his former students, have announced a significant milestone in materials and electronics engineering: the creation of what they call “rubbery CMOS,” which provides the same functionality as conventional CMOS (complementary metal–oxide–semiconductor) circuits, but is made from entirely different materials.

The great benefit of rubbery CMOS is that it provides the circuit functionality of conventional CMOS while also being stretchable and deformable.

CMOS technology underpins nearly all modern electronics, from smartphones and laptops to sensors and displays. As its name suggests, CMOS relies on rigid metals and oxides that easily crack when bent or stretched, leading to device failure. For years, with the goal of enabling next-generation devices that can move and flex like biological tissue, researchers have sought stretchable electronic materials that can retain performance under deformation.

Most efforts so far have combined conventional semiconductors, such as silicon, with stretchable substrates like polymers. While these hybrid systems can sustain some deformation, they lack true material-level elasticity and are thus unsuitable for intimate, conformal integration with soft biological tissues or dynamically deformable surfaces.

That limitation has fueled growing interest in a new frontier: rubbery electronics, wherein every functional component – from the semiconductor to the dielectric and interconnect – is made of rubbers that are intrinsically stretchable.

“For rubber electronics, you don’t use any metal, don’t use oxides, and don’t use conventional semiconductors,” explained Yu, who is a Founder Professor of Engineering in the Department of Electrical and Computer Engineering at the University of Illinois Urbana-Champaign. “It’s still a transistor, but it doesn’t rely on conventional MOS materials.”

Until now, however, efforts to achieve the full CMOS architecture and complementary behavior in rubbery electronics – by integrating both p-type and n-type rubbery transistors (that is, both positive and negative charge carriers) in a matched and coordinated manner – have remained at an early stage, with very limited results.

“The field has been demonstrating primarily p-type materials, which transport positively charged electrical carriers,” Yu said. “We’ve never before demonstrated true CMOS behavior in rubber electronics.”

That breakthrough has now been achieved. In the new paper, the team reports fully stretchable complementary integrated circuits composed of both elastic n-type and p-type transistors. These devices retain stable electrical performance even when stretched by up to 50 percent. Moreover, digital logic gates fabricated from these components also maintain robust function under large mechanical strains.

As a proof of concept, the researchers developed a “sensory skin”: a thin, stretchable electronic layer that can adhere intimately to human skin, as shown in the accompanying photo. This innovation paves the way for medical and health-monitoring applications, for which electronic systems must conform to soft, dynamically moving tissues.

Yu said that his team’s work in this area was initially motivated by medical implant applications, but that the implications go far beyond biomedicine.

“Soft robotics and human–machine interfaces are natural next steps,” he said. “Imagine a wearable glove made of integrated circuits that can both sense and process information directly within the glove!”

Illinois Grainger Engineering Affiliations

Cunjiang Yu is a Founder Professor in Engineering with a primary appointment in the Department of Electrical and Computer Engineering. He also has appointments in the Department of Materials Science and Engineering, the Department of Mechanical Science and Engineering, and the Department of Bioengineering, as well as the Beckman Institute for Advanced Science and Technology, the Materials Research Laboratory, and the Nick Holonyak Micro and Nanotechnology Laboratory.