Researchers from Caltech have created a new electronic skin or e-skin, that is applied directly to the top of the real skin on a person. The e-skin is made from a soft, flexible rubber material that can be embedded with sensors that monitor health information. Health information the sensor is capable of recording includes heart rate, body temperature, blood sugar, and metabolic byproducts that are indicators of health.
The wearable sensor can also record nerve signals that control muscles. The sensor runs solely on biofuel cells powered by the body’s waste product, sweat. The scientists say that human sweat contains very high levels of a chemical called lactate. Lactate is a compound generated as a byproduct of normal metabolic processes, especially by muscles during exercise.
The fuel cells built into the e-skin can absorb the lactate and combine it with oxygen from the atmosphere to generate water and pyruvate, which is another byproduct of metabolism. The biofuel cells can generate enough electricity to power sensors and a Bluetooth device similar to the type that connects a phone to a car stereo.
The team chose Bluetooth connectivity because it has extended connectivity for practical medical and robotic applications, even though it consumes more power than near-field communications. In addition to creating a power source that’s able to run on sweat, the team was also challenged by needing to create a sensor that can last a long time with minimal degradation. The file cells are made using carbon nanotubes pregnant with platinum/cobalt catalyst in a composite mesh that holds an enzyme able to break down lactate.
The fuel cells can generate continuous, stable power output as high as several milliwatts per square centimeter over multiple days using human sweat. The researchers plan to develop a variety of sensors that can be embedded in the e-skin allowed to be used for numerous purposes. The scientists intend this to be a platform and note that it could be used as a human-machine interface.