Bark biosensors transmit a Bluetooth signal without batteries or wires

Engineers created a biosensor made of lignocellulose nanofibrils derived from tree bark. The self-powered prototype device sends data to a smartphone via Bluetooth.

Researchers at the University of Toronto used materials derived from wood to create a triboelectric nanogenerator for wearable biosensors. The engineers believe the new device could be used to track biometric data such as heart rate, oxygen levels or skin conductance.

Biosensors are common in wearable electronics, but today they are battery-powered, making the devices bulky and requiring constant charging. Engineers believe battery-free sensors could be thinner, smaller and cheaper. In their paper, published in the journal Nano Energy, the scientists use the triboelectric effect, a type of static electricity, to create a natural sensor.

The researchers note that many engineers are working on using the triboelectric effect to power wearable devices. But most current designs use synthetic materials such as polytetrafluoroethylene (Teflon). The new material consists of nanofibrils, tiny filaments of plant material that are hundreds of thousands of times thinner than a human hair.

In the experiment, scientists showed that the new device generates 160% more voltage and 140% more current than a similar device using polytetrafluoroethylene. The power of the device during testing was enough to send a radio-frequency signal every three minutes, which was picked up by a nearby smartphone.