Sweat and charge the batteries
Electronic tattoo will be powered by human sweat
Asya Gorina, "Vesti" based on the materials of the American Chemical Society: Tattoo biobatteries produce power from sweatThe ranks of wearable biomedical sensors have been replenished with a new development of engineers from the University of California San Diego: a small electronic tattoo is attached to a person's body and monitors his health during physical training.
The device will be powered by human sweat, which is released in excess during medium and high intensity loads.
The scientists described their development in a report they read at the 248th Annual Meeting of the American Chemical Community. The principle of operation of the device is based on the detection and reaction of sensors to lactic acid – a substance present in the composition of sweat.
"The level of lactate can tell a lot about the state of the body during exercise," explains the lead author of the study Wenzhao Jia (Wenzhao Jia).
The more intense the workout, the more lactic acid is produced. During strenuous physical activity, the body must generate more energy, so a process called glycolysis is activated. During it, energy is produced and lactate is released, which can be detected in the blood.
The problem is that in order to monitor the level of physical activity, the amount of lactic acid in the blood must be analyzed quite often during various physical activities. And collecting samples and analyzing them takes a lot of time and effort.
Therefore, Jia and her colleagues have developed the most convenient way to measure the lactate content during exercise. They implanted a small flexible sensor into a stretchable film that can be attached to the skin as a temporary tattoo. The sensor contains an enzyme that catches electrons from lactate, generating a weak electric current.
A diagram from the article by Wenzhao Jia et al. Epidermal Biofuel Cells: Energy Harvesting from Human Perspiration
(Angewandte Chemie, 2013) – VM.
To test the technology, the researchers invited 10 healthy volunteers to their laboratory and attached newly invented sensors to their skin. During the experiment, the scientists measured the electric current produced by the device during the physical training of the subjects – they pedaled the exercise bike for half an hour with a gradual increase in the resistance level. In this way, the researchers were able to continuously monitor lactate levels in sweat over time and with changes in exercise intensity.
Later, Jia and her team decided to turn sweat into a bioaccumulator power source. Batteries produce energy when a current passes in the form of electrons from the anode to the cathode. In this case, the anode contained an enzyme that extracted electrons from lactate, and the cathode contained a molecule that received electrons.
Fifteen volunteers who trained on an exercise bike with a tattoo on their body produced various amounts of electricity. Interestingly, those who trained on average less than once a week produced more energy than those who were subjected to physical activity from one to three times a week. The least energy was produced by those who prefer almost daily sports.
The maximum productivity recorded among the volunteers from the "unsportsmanlike" group was 70 microwatts per square centimeter of skin.
"This is not so much in the usual sense, but we are already working on increasing the potential of the device. Ultimately, we need to bring the technology to such a level that sweat can power small electronic devices. Right now we can get a maximum of 70 microwatts per square centimeter, but our electrodes are only 2-3 millimeters wide and generate about 4 microwatts. To power, for example, hours, it takes at least 10 microwatts," Jia explains.
In the future, scientists will also have to solve the problem of energy storage and its reasonable consumption. However, their bioaccumulator already has great advantages over analogues: it is biologically compatible, does not emit toxic substances and uses renewable energy sources.
Portal "Eternal youth" http://vechnayamolodost.ru20.08.2014