Wearable devices designed for continuous biometric monitoring pose unique challenges in terms of power sources. A solution must be durable, comfortable, and convenient. We’ve written about flexible, stretchable batteries that can conform to various shapes and sizes while providing sufficient and reliable electrical power for wearable electronics. Binghampton University, SUNY researchers developed a bacteria-powered, textile-based stretchable biobattery that uses sweat as fuel for a microbial fuel cell. Nearly five years ago we noted work at Fudan University in China on a stretchable fiber battery constructed with multiwall carbon nanotubes coated with different lithium oxides to create anode and cathode fibers.

Researchers at Stanford University developed a lithium-ion battery (LIB) with a solid, stretchable polymer electrolyte that carries a charge between battery poles. The Stanford team addresses the safety issue associated with lithium-ion batteries catching fire. Watching video footage of a Tesla or other EV in flames because of battery integrity failure is bad enough — no one wants to experience or see a health tech wearable on fire.

As described in Nature Communications, the solid polymer improves on the flammable liquid electrolytes that are used in LIB designs. The Stanford team’s development efforts focus on balancing high conductivity, mechanical robustness, and conformability. To date, the group has produced a thumbnail-sized stretchable battery prototype that stores approximately half the energy of conventional batteries.

The next steps for the Stanford researchers include increasing energy density, building larger working versions, and designing proof-of-concept experiments that demonstrate the technology’s capabilities. Members of the battery team are also developing BodyNet, a network of stretchable sensors that stick to the skin to monitor vital signs. A Stanford University engineering publication suggests an application combining the two stretchable technologies would be an opportunity to highlight the respective projects.