Post From This Category




Six Effects of Enzymes in the Human Body

Six Effects of Enzymes in the Human Body

Do you know when enzymes begin to be produced in the human body? The answer is that they existed during the egg and sperm period. It is also because of the activity of the enzyme that the egg and sperm can be combined. Cell division must use enzyme because the medium,...

5G in new directions just got Weird

5G in new directions just got Weird

Industry group 3GPP takes 5G in new directions in the latest set of standards The only reason you’re able to read this right now is because of the Internet standards created by the Internet Engineering Task Force. So while standards may not always be the most exciting...

Researchers Turning Bricks Into Supercapacitors in 2020

Researchers Turning Bricks Into Supercapacitors in 2020

Researchers at Washington University in St. Louis made a fast energy storage device out of common building bricks As solar panels and wind turbines multiply, the big problem is how with how to store all the excess electricity produced when the sun is up or the wind...

Human Sperm Don’t Swim Like We Thought

Human Sperm Don’t Swim Like We Thought

3D microscope reveals that sperm have been fooling scientists for 350 years For more than three centuries scientists have believed that human sperm swim by swishing their tails in a side-to-side, symmetrical motion. But that’s because we’ve been...

Path to Powerful Analog AI found by Startup and Academics

Path to Powerful Analog AI found by Startup and Academics

Equilibrium propagation allows all-analog training Engineers have been chasing a form of AI that could drastically lower the energy required to do typical AI things like recognize words and images. This analog form of machine learning does one of the key mathematical...

Spherical Silicon Solar Cells Absorb Scattered Sunlight

Spherical Silicon Solar Cells Absorb Scattered Sunlight

Silicon solar cells folded into spheres hint at solar power's flexibility in even small devices By Jeremy Hsu The spherical solar cell also delivered about 60 percent more power output than its flat counterpart when both could collect only scattered sunlight under a...










Why Sweat Will Power Your Next Wearable

by | Jul 23, 2020 | Tech News | 0 comments




Biofuel cells can generate enough watts for fitness trackers and health monitors- By Patrick Mercier and Joseph Wang

Here’s how a wearable turns sweat into energy: A fuel cell consists of two electrodes—an anode and a cathode—with an electrolyte between them. The fuel goes into the anode, where a catalyst separates its molecules into electrons and protons. The protons pass through a membrane to the cathode, while the electrons flow into a circuit. The Welsh scientist William Robert Grove first worked out the process in 1839; he used hydrogen as the fuel and oxygen as the catalyst to generate water and electrical current.

Hydrogen is impractical for a wearable fuel cell because it’s highly flammable. Sweat, on the other hand, is easily acquired and abundant, particularly when a person is exercising or playing sports. And, given that athletes embraced all sorts of wearables early and widely, they represent an attractive early market for sweat-powered devices.

Sweat isn’t just water. It contains trace amounts of a wide variety of minerals and other substances like glucose and lactate. These substances, called metabolites, are by-products of the chemical processes that constantly go on inside living beings, and they make attractive biofuels. We are particularly interested in lactate, because its concentration in sweat rises with exertion. In our sweat biofuel cells, we create a layer of enzymes that reacts with the lactate in sweat to split the electrons and protons and create an electrical current.

Photo-group showing how a wearable turns sweat into energy.
Photos: Center for Wearable Sensors/University of California, San Diego
Biofuels On Board: To make fuel cells flexible enough to be used in wearables [left column], researchers at the University of California, San Diego, designed anodes and cathodes as a series of “islands” connected by serpentine coils. The coils unwind under stress, allowing the structure to flex and stretch. The researchers capped each anode and cathode with carbon nanotubes, creating 3D pellets to increase the effective surface area of the electrodes. To test this design, they built a circuit board that included a Bluetooth radio and a microprocessor, along with a voltage converter and other peripheral components [bottom right]. Then they put it all together in an armband, shown here harvesting energy from the sweat of graduate student Amay Bandodkar [top right].

We’re not the first researchers to think of using body fluids as fuel. Some of the original pacemaker and cochlear implants proposed in the 1970s were intended to use glucose biofuel cells for power. Given the abundance of biofuels inside the body, using them for implantable devices was a logical choice. The main drawback was that the enzymes used to catalyze the fuel cell reaction would degrade, and the electrode would stop functioning within a few days. The only way to restore the fuel cell’s operation was to surgically remove the implant, which was obviously impractical.

To avoid the enzyme-depletion issue, our group instead has focused on developing disposable wearables worn outside the body. We demonstrated our first biofuel cells in 2014. The lactate biofuel cells were screen-printed onto a fabric headband and a wrist-worn sweat guard.

graph
Inside Story: To turn sweat into power for a digital watch or other wearable devices, a fuel cell uses a layer of enzymes that react with the lactate in sweat to split the electrons and protons. The protons pass through a membrane to the cathode, while the electrons flow into a circuit, powering the device.

There’s one more hurdle to bringing sweat power to wearables: In most situations, people don’t sweat constantly—or at least not heavily enough to generate much power. If you’re not sweating, your fuel cell will run dry and stop producing power. This may not be an issue in applications like exercise and athletics, but it’s a big deal in most other cases.

There are three ways to work around this limitation. We could use the scavengers only for applications where the availability of sweat is guaranteed. Or we could add an energy-storage element to the wearable. Or, finally, we could add a complementary, nonbiofuel energy scavenger to the wearable.

We don’t want to limit the applications to athletes in action, so we’ve been focusing on the two latter approaches. For wearables that need a constant supply of energy—for example, smart watches—an obvious solution is adding a battery or an ultracapacitor to act as an energy buffer. If the fuel cell has a high power density but the availability of power is intermittent, then the wearable device will charge its battery when power is available and discharge the battery when the biofuel cell stops producing power.

This energy buffer needs to have the same general physical properties as the rest of the wearable. It doesn’t make sense to have a biofuel cell that’s small, soft, and stretchable if the battery on top is large and rigid.

Last year, researchers in our center created a stretchable textile that uses sweat to feed its biofuel module and stores the energy in a flexible supercapacitor. We’ve also demonstrated stretchable and rechargeable zinc-silver-oxide battery prototypes, made using printed electronics. These stretchy batteries can be recharged hundreds of times and can generate relatively high currents, although their energy densities have a long way to go before they can match those of their rigid counterparts.

To increase the likelihood of successful energy harvesting and therefore decrease the demands on the energy buffer, we’re also looking at using multiple types of energy scavenging to power a single wearable. Users may not necessarily sweat all the time, but if their wearable combines a biofuel cell with a solar cell and a thermoelectric generator, then the chances of any one of these devices generating power at a particular time is going to be higher than with one of them acting alone.
Of course, integrating several scavenging technologies needs to happen without compromising the wearer’s comfort. As with the biofuel cell–energy buffer combination, we have to make these gadgets small, soft, and stretchy. Researchers have lately been considering how to redesign energy-scavenging devices for better integration into what we like to call an energy sandwich—that is, a collection of energy scavengers stacked in a single small, stretchable device. In 2018 we developed a small circuit that can simultaneously extract energy from multiple sources and send it to multiple wearables and a battery simultaneously.

About the Authors

Patrick Mercier is an associate professor of electrical and computer engineering and Joseph Wang is a professor of nanoengineering at the University of California, San Diego. Mercier and Wang are also co-director and director, respectively of the university’s Center for Wearable Sensors.










200 CIVIL ENGINEERING Interview Questions & Answers

200 CIVIL ENGINEERING Interview Questions & Answers

200 CIVIL ENGINEERING Interview Questions & Answers 1. What are the causes of building collapse?The passage of time is one reason. Buildings also collapse due to weak foundations. Earthquakes, hurricanes and other natural disasters can also damage the structure of...

Tesla Valve Working

Tesla Valve Working

Nikola Tesla had invented a very interesting one-way value. Let's understand the complete physics of this valve in this video. https://youtu.be/suIAo0EYwOE

Jobs in TATA

Jobs in TATA

Search job [wp-rss-aggregator template="govt-job"]

%d bloggers like this: