Electronics have become increasingly mobile, following us everywhere into our daily lives. Today, it’s not only common for people to carry their notebooks and smartphones with them, but also have embedded electronics in their clothing and even on their skin.

However, wearable electronics currently face physical limitations because, traditionally speaking, silicon chips haven’t been designed to stretch like fabrics. The most limiting factor, though, is the battery, which can be challenging to make flexible — until now.

Writing in the journal Nature Communications, Stanford scientists have described a novel power source that can stretch and bend the way our bodies can.

The breakthrough was made by using polymers (plastic) in the battery. This isn’t a new idea, but previous setups that used polymers in lithium-ion batteries in the form of flowable gels caused leaks or even burst into flame.

To avoid this risk, Stanford chemical engineers Zhenan Bao and Yi Cui used a type of polymer that is both solid and stretchable rather than a gooey material that could potentially leak. The challenge lied in finding the right kind of plastic that could still transport electric charge effectively between the battery’s anode and cathode.

In one experiment, the researchers’ thumbnail-sized prototype maintained a constant power output despite being squeezed, folded, and stretched to nearly twice its original length. Its energy density, mass for mass, is about half that of a comparably sized non-stretchable battery.

In the future, the team wants to continue their research, looking to increase the energy density and demonstrate larger versions of the device outside the lab.