Lactic acid instead of batteries
Employees of the California Institute of Technology have developed an "electronic skin" that is superimposed directly on top of the real one. It is made of soft elastic rubber and can be equipped with sensors that collect information such as heart rate, body temperature, blood sugar and other health indicators.
One of the main problems of such devices is power consumption. Researchers have to use batteries, solar cells or accumulate the energy of human movement. The new electronic skin is equipped with biofuel elements that work exclusively on one of the body's waste products.
Human sweat contains a high level of lactic acid (lactate) – it is a byproduct of normal metabolic processes, especially a lot of it is produced in the muscles during training. Fuel cells embedded in electronic skin absorb lactate from sweat and combine it with oxygen from the atmosphere, generating water and pyruvate, another byproduct of metabolism. During operation, biofuel cells generate enough electricity to operate sensors and a Bluetooth device that provides the ability to transmit readings wirelessly to a computer.
Bluetooth communication consumes more power, but despite this, it is a more attractive approach with advanced connectivity for practical medical and robotic applications.
Developing a sweat-powered power source wasn't the only challenge in creating an electronic skin. It should also function for a long time with high energy intensity with minimal degradation.
Biofuel elements are made of carbon nanotubes impregnated with a platinum-cobalt catalyst and a composite mesh containing an enzyme that breaks down lactate. They can generate continuous, stable power output (3.5 milliwatts per square centimeter) for several days from untreated human sweat. In tests, they maintained a stable power level for 60 hours of continuous operation. The electronic skin selectively monitored key metabolic parameters (urea, ammonium, glucose and pH) and skin temperature during prolonged physical exertion and wirelessly transmitted data to the user interface using Bluetooth. It is also able to control muscle contraction and work as a human-machine interface when using prosthetics.
Currently, the group is engaged in the development of various sensors that can be integrated into the electronic shell. The vital information obtained with the help of this platform can be used both for monitoring the state of human health and for designing and optimizing next-generation prostheses.
Article by Y.Yu et al. Biofuel-powered soft electronic skin with multiplexed and wireless sensing for human-machine interfaces is published in the journal Science Robotics.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on Caltech materials: Electronic Skin Fully Powered by Sweat Can Monitor Health, Serve as Human-Machine Interface.