Your gadget’s next power supply? Your body
Searching for a power outlet may soon become a thing of the past. Instead, devices will receive electricity from a small metallic tab that, when attached to the body, is capable of generating electricity from bending a ¿nger and other simple movements.
That’s the idea behind a collaborative research project led by University at Buffalo (UB) and Institute of Semiconductors (IOP) at Chinese Academy of Science (CAS), sciencedaily.com wrote.
The tab — a triboelectric nanogenerator — is described in a study published in the journal Nano Energy.
Lead author Qiaoqiang Gan, PHD, associate professor of electrical engineering in UB’S School of Engineering and Applied Sciences, said, “No one likes being tethered to a power outlet or lugging around a portable charger.
“The human body is an abundant source of energy. We thought: Why not harness it to produce our own power?”
Triboelectric charging occurs when certain materials become electrically charged after coming into contact with a different material. Most everyday static electricity is triboelectric.
Researchers have proposed numerous nanogenerators that utilize the triboelectric effect; however, most are dif¿cult to manufacture (requiring complex lithography) or are not cost effective.
The tab that the UB and CAS team are developing addresses both of those concerns.
It consists of two thin layers of gold, with polydimethylsiloxane (also called PDMS, a silicon-based polymer used in contact lenses, Silly Putty and other products) sandwiched in between.
Key to the device is that one layer of gold is stretched, causing it to crumple upon release and create what looks like a miniature mountain range.
When that force is reapplied, for example from a ¿nger bending, the motion leads to friction between the gold layers and PDMS.
Another lead author, Yun Xu, PHD, professor of IOP at CAS, said, “This causes electrons to Àow back and forth between the gold layers. The more friction, the greater the amount of power is produced.”
The study describes a small tab (1.5 centimeters long, by one centimeter wide).
It delivered a maximum voltage of 124 volts, a maximum current of 10 microamps and a maximum power density of 0.22 mill watts per square centimeter.
That’s not enough to quickly charge a smartphone; however it lit 48 red LED lights simultaneously.
Coauthors of the study include Huamin Chen at IOP and CAS; and Nan Zhang, a PHD student at UB.
Because the tab is easily fabricated, Zhang is leading a team of UB undergraduates which is tasked with improving the tab’s performance.
The team plans to use larger pieces of gold, which when stretched and folded together are expected to deliver even more electricity.
Researchers are also working on developing a portable battery to store energy produced by the tab.
They envision the system serving as a power source for various wearable and selfpowered electronic devices. The Red Planet’s low gravity and lack of magnetic ¿eld makes its outermost atmosphere an easy target to be swept away by the solar wind, but new evidence from ESA’S Mars Express spacecraft shows that the Sun’s radiation may play a surprising role in its escape.
Why the atmospheres of the rocky planets in the inner solar system evolved so differently over 4⅔ billion years is key to understanding what makes a planet habitable, phys.org wrote.
While Earth is a life-rich waterworld, our smaller neighbor Mars lost much of its atmosphere early in its history, transforming from a warm and wet environment to the cold and arid plains that we observe today.
By contrast, Earth’s other neighbor Venus, which although inhospitable today is comparable in size to our own planet, and has a dense atmosphere.
One way that is often thought to help protect a planet’s atmosphere is through an internally generated magnetic ¿eld, such as at Earth.
The magnetic ¿eld deàects charged particles of the solar wind as they stream away from the Sun, carving out a protective ‘bubble’ — the magnetosphere — around the planet.
At Mars and Venus, which don’t generate an internal magnetic ¿eld, the main obstacle to the solar wind is the upper atmosphere, or ionosphere.
Just as on Earth, solar ultraviolet radiation separates electrons from the atoms and molecules in this region, creating a region of electrically charged — ionized — gas: The ionosphere.
At Mars and Venus this ionized layer interacts directly with the solar wind and its magnetic ¿eld to create an induced magnetosphere, which acts to slow and divert the solar wind around the planet.
For 14 years, ESA’S Mars Express has been looking at charged ions, such as oxygen and carbon dioxide, Àowing out to space in order to better understand the rate at which the atmosphere is escaping the planet. The study has uncovered a surprising effect, with the Sun’s ultraviolet radiation playing a more important role than previously thought.
Robin Ramstad of the Swedish Institute of Space Physics, and lead author of the Mars Express study, said, “We used to think that the ion escape occurs due to an effective transfer of the solar wind energy through the Martian induced magnetic barrier to the ionosphere.
“Perhaps counter-intuitively, what we actually see is that the increased ion production triggered by ultraviolet solar radiation shields the planet’s atmosphere from the energy carried by the solar wind, but very little energy is actually required for the ions to escape by themselves, due to the low gravity binding the atmosphere to Mars.”
The ionizing nature of the Sun’s radiation is found to produce more ions than can be removed by the solar wind.
Although the increased ion production helps to shield the lower atmosphere from the energy carried by the solar wind, the heating of the electrons appears to be suf¿cient to drag along ions under all conditions, creating a ‘polar wind’.
Mars’ weak gravity — about one third that of Earth’s — means the planet cannot hold on to these ions and they readily escape into space, regardless of the extra energy supplied by a strong solar wind.
At Venus, where the gravity is similar to Earth’s, a lot more energy is required to strip the atmosphere in this way, and ions leaving the sunward side would likely fall back towards the planet on the lee-side unless they are accelerated further.
Ramstad said, “We therefore conclude that in the present day, ion escape from Mars is primarily production-limited, and not energy-limited, whereas at Venus it is likely to be energy-limited given the larger planet’s higher gravity and high rate of ionization, being nearer to the Sun.
“In other words, the solar wind likely only had a very small direct effect on the amount of Mars atmosphere that has been lost over time, and rather only enhances the acceleration of already escaping particles.”
Dmitri Titov, ESA’S Mars Express Project Scientist, said, “Continuous monitoring of Mars since 2004, which covered the change in solar activity from solar minimum to maximum, gives us a large dataset that is vital in understanding the long-term behavior of a planet’s atmosphere and its interaction with the Sun.
“Collaboration with NASA’S MAVEN mission, which has been at Mars since 2014, is also allowing us to study the atmospheric escape processes in more detail.”
The study also has implications for the search for Earth-like atmospheres elsewhere in the Universe.
Dmitri said, “Perhaps a magnetic ¿eld is not as important in shielding a planet’s atmosphere as the planet’s gravity itself, which de¿nes how well it can hang on to its atmospheric particles after they have been ionized by the Sun’s radiation, regardless of the power of the solar wind.”