A group of researchers managed to stack and connect layers of electronics on top of each other to essentially build 3D stretchable electronics that can serve complex and diverse functions while remaining low in size.

The proof of concept, compared to a US dollar coin. Image credits: Zhenlong Huang / University of California San Diego.

Smart everything

Few things have revolutionized our world like electronics. In our pockets, we carry smartphones — devices which not only allow us to call essentially anyone in the world but also to access all the world’s knowledge and content at the click of a button; they’re good for playing silly games, too. But phones aren’t the only things getting smart. We have smart cars, smart homes, and even smart clothes — all thanks to the ever-advancing electronics.

But there are limits. Building 3D electronics that are small enough and able to carry out complex functions has proven very challenging.

“Our vision is to make 3D stretchable electronics that are as multifunctional and high-performing as today’s rigid electronics,” said senior author Sheng Xu, a professor in the Department of NanoEngineering and the Center for Wearable Sensors at the UC San Diego Jacobs School of Engineering.

The new technology can have far-reaching implications. For instance, consider smart sensors — a stretchable electronic bandage could be used to monitor patient’s body functions such as respiration, body motion, temperature, eye movement, heart and brain activity. Xu and colleagues built a prototype, which can do all this and control a robotic arm.

“Rigid electronics can offer a lot of functionality on a small footprint–they can easily be manufactured with as many as 50 layers of circuits that are all intricately connected, with a lot of chips and components packed densely inside. Our goal is to achieve that with stretchable electronics,” said Xu.

The new device consists of four layers of interconnected, stretchable, flexible circuit boards, featuring so-called “island-bridge” design. The “island” is a small, rigid electronic part (sensor, antenna, Bluetooth chip, amplifier, accelerometer, resistor, capacitor, inductor, etc.), while the “bridge” is made of thin copper wires which allow the circuits to twist and bend without losing functionality.

Researchers say they don’t have a specific purpose in mind, but the potential applications are limitless — wherever flexible circuits and electronics are necessary, the new technology could do wonders.

“We didn’t have a specific end use for all these functions combined together, but the point is that we can integrate all these different sensing capabilities on the same small bandage,” added co-first author Zhenlong Huang, a visiting Ph.D. student in Xu’s research group.

The new device has been shown to function for six months without losing any of its functionality or power. The team is now working with to improve and finesse the technology. Hopefully, it won’t be long before the technology is tested in a clinical setting.

The study has been published in Nature Electronics.