Image of Newly Developed Materials Science
The newly developed liquid electret material (left) and the bendable and stretchable vibration-powered device (middle and right). (Credit: National Institute for Materials Science)

A liquid electret material capable of semi-permanently retaining static electricity was used to create the world’s first bendable, stretchable vibration-powered device. Because this device is highly deformable and capable of converting very subtle vibrations into electrical signals, it could be used to develop devices such as self-powered heartbeat and pulse sensors.

The researchers shielded porphyrin — an organic compound — with a flexible yet insulating structure (i.e., branched alkyl chains), thereby developing a liquid material at room temperature which is able to stably retain static charge on the porphyrin unit. They subsequently developed a bendable and stretchable vibration-powered device.

First, a high voltage was applied to this liquid material, thereby electrically charging it. The liquid material was then allowed to soak into a stretchable textile and the soaked textile was then sandwiched between soft, polyurethane electrodes integrated with silver-plated fibers as a wiring material. When the surface of the device is pressed with a fingertip, it generates a voltage in a range of ±100–200 mV and operates stably for at least 1.5 months.

The group hopes to achieve healthcare use of this device by enhancing the ability of the liquid electret material to retain static electricity and making modifications to the processing techniques applied to the device.