Could your workout charge your smartphone?

Date: Aug-18-2014 One day, your morning gym workout or jog could not only be recharging you, but also

recharging your smartphone or other small electronic device. Scientists have developed a

biosensor mounted inside a temporary tattoo that can monitor the wearer's progress as they

exercise and harness their sweat to produce electrical power.

Biobatteries recharge more quickly than conventional batteries, they use renewable energy, and they do not explode or leak toxic chemicals.

The innovation is the work of a team led by Joseph Wang, Distinguished Professor and Chair of

Nanoengineering at the University of California. They presented their novel biobattery approach

at a recent

meeting of the American Chemical Society in San Francisco.

Compared with conventional batteries, biobatteries have several advantages: they recharge more

quickly, they use renewable energy (in this case body sweat), and they do not explode or leak

toxic chemicals.

Prof. Wang says their work shows "the first examples of epidermal electrochemical biosensing

and biofuel cells that could potentially be used for a wide range of future applications."

As we sweat, we produce lactate, "a very important indicator of how you are doing during

exercise," says Dr. Wenzhao Jia, a postdoctoral student in Prof. Wang's lab.

Generally, the more intensely we exercise the more lactate we produce, as aerobic respiration

is not enough to produce the energy we need, and anaerobic respiration kicks in. Anaerobic

respiration converts glucose or glycogen to lactic acid, generating energy in the process.

Professional athletes monitor their lactate levels to evaluate their fitness and training

performance. Doctors also asses lactate levels during exercise to test patients for heart or lung

disease, and other conditions marked by unusually high lactate.

Non-invasive, real-time measure of lactate levels during exercise

Dr. Jia and her colleagues have developed a faster, easier and non-invasive way to measure

lactate during exercise in real time. Before their innovation, the only way to do this was by

taking blood samples at regular intervals during exercise and sending them away for analysis.

The new sensor, which can be imprinted onto a temporary tattoo, contains an enzyme that

produces a weak electrical current by stripping electrons from lactate molecules.

The scientists tested the new device on 10 healthy volunteers. They applied the temporary

tattoos to the upper arms of the volunteers and measured how much electrical current they

produced as they exercised.

The volunteers exercised on stationary bikes for 30 minutes, with resistance gradually

increasing over the period. The sensors allowed the scientists to monitor sweat lactate levels as

they changed with exercise intensity.

Biobattery uses lactate from sweat to generate power

The team then developed the technology a stage further and made a sweat-powered

biobattery.

They used the enzyme that strips the lactate of electrons to act as the anode, and used a

chemical that accepts the electrons to be the cathode. Electrons moving from an anode to a

cathode is the basic principle on which a battery works.

To see how the device works, play the video below.

The team tested the biobattery on 15 volunteers exercising on stationary bikes. As before, the

device was incorporated within a temporary tattoo applied to their upper arms.

The different volunteers produced varying amounts of power in their tattoo biobatteries.

Curiously, the less fit volunteers appeared to produce the most power. Those who exercised only

once a week produced more power than those who exercised at least three times a week.

One possible explanation is that less fit people become fatigued more quickly, causing

lactate-producing anaerobic respiration to kick in earlier.

The less fit volunteers produced around 70 μW per square cm (cm2) of skin. Dr. Jia

says this is not a large amount of current, but they are working on how to to enhance it so it

could eventually be enough to power small electronic devices:

"Right now, we can get a maximum of 70 μW per cm2, but our electrodes are only 2 by 3

millimeters in size and generate about 4 μW - a bit small to generate enough power to run

a watch, for example, which requires at least 10 μW."

She says they also need to find a way to store the generated current.

The National Science Foundation and Office of Naval Research are funding the work.

Medical News Today also recently reported how an engineer at Stanford University is

working on wireless powering of

medical implants deep inside the body.

Written by Catharine Paddock PhD

View all articles written by Catharine, or follow her on:

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.