Nanogenerator Harvests Swipes To Power LCD Screens


There’s a whole lot of energy out there that’s just kind of hanging around. The brakes on cars and trains turn momentum into heat, for example, which we now have systems for recapturing and recycling. But there are many more examples of wasted “ambient” energy that we don’t recapture. Even regular old walking around as bipedal animals is an inefficient process; the energy we expend in a single stride is greater than it would be given a perfectly efficient process.

Such is life, but nowadays we’re surrounded by devices that don’t require all that much power to operate. A couple of volts goes a long way. A newly developed nanogenerator, described this week in the journal Nano Energy, puts that into perspective, offering a means of converting the energy expended in a standard touchscreen swipe into sufficient power to light up a touchscreen.

The nanogenerator in question is what’s known as a biocompatible ferroelectret nanogenerator, or FENG—a paper-thin sheet of layered materials including silver, polyimide, and a sort of giant charged molecule known as polypropylene ferroelectret. The layers of the FENG are loaded up with charged ions, which results in a construction that, when compressed, produces electrical energy.

The high-level picture is that the FENG winds up with really huge dipoles—magnetic poles of opposite charge—existing on its different layers, which then change in relation to each other as the material is deformed under pressure. This change results in differences in electrical potential, which is what gives us useful electrical energy.

So, we hear about self-powered devices kind of a lot. What makes this one interesting is that it’s a new kind of device. That is, a FENG is not piezoelectric (electricity via squishing crystals) or triboelectric (electricity via certain kinds of friction).

The paper describes some advantages: “their simple fabrication allows for encapsulated low-cost devices. In view of the environment, health, and safety, the fabrication of encapsulated FENG avoids the use of harmful elements (e.g. lead) or toxic materials (e.g. carbon nanotubes), making it more attractive for biocompatible and perhaps even implantable applications.”

The device also has the neat property of becoming more powerful when folded. In a statement, lead investigator Nelson Sepulveda explains: “Each time you fold it you are increasing exponentially the amount of voltage you are creating. You can start with a large device, but when you fold it once, and again, and again, it’s now much smaller and has more energy. Now it may be small enough to put in a specially made heel of your shoe so it creates power each time your heel strikes the ground.”

Sepulveda and co.’s current task is in developing technology that would allow for the transmission of energy generated by said heel strike into devices like headsets.

Scientists have developed a material that generates electricity simply by touching it.


Welcome to the future of touchscreens.

Scientists have developed a flexible, film-like material that generates electrical energy when touched, meaning devices like smartphones and tablets could one day be powered simply by people using them.

And beyond just touchscreen gadgets, the researchers say the thin, flexible device could also be used in our clothing or shoes, helping us harvest energy from our body movements potentially all day long.

“We’re on the path toward wearable devices powered by human motion,” says electrical engineer Nelson Sepulveda from Michigan State University.

“What I foresee, relatively soon, is the capability of not having to charge your cell phone for an entire week, for example, because that energy will be produced by your movement.”

The film the researchers have created is what’s known as a nanogenerator, in which energy is produced by a small-scale physical change, such as the tap or swipe of a finger.

In this case, the device works on the principle of piezoelectricity, where an electric charge accumulates in response to applied mechanical stress.

What makes this possible is the interaction between the substances that make up the film.

The core structure is a silicon wafer, which is then layered with thin sheets of other materials, including silver, polyimide, and polypropylene ferroelectret, which serves as the active material in the device.

Polypropylene ferroelectret is a thin polymer foam that contains charged particles. When pressure is applied to the device, the foam layer compresses, creating a change in what’s called dipole moments – an interaction between positive and negatively charged molecules in the ferroelectret.

This in turn generates an electric charge, and as you can see in the videos below, it’s one that’s capable of powering the kinds of devices we use every day, like a touch-sensitive keyboard:

 

While it’s true that none of those devices require much power, it’s a promising start to a wholly new kind of piezoelectric generator – especially given that it includes an amazing ability to multiply its output when folded.

“Each time you fold it you are increasing exponentially the amount of voltage you are creating,” says Sepulveda.

“You can start with a large device, but when you fold it once, and again, and again, it’s now much smaller and has more energy. Now it may be small enough to put in a specially made heel of your shoe so it creates power each time your heel strikes the ground.”

In testing, a hand-sized sheet of the material was able to generate about 50 volts, but the researchers acknowledge they currently have no way to create a stable current from the material.

As you can see in the videos, every time the researchers interact with their prototypes, the lights or displays activate, but as soon as they remove the applied pressure, the devices become inert once more.

Figuring out how to concert the voltage into a steady flow of useable current will be the next challenge for the team.

They’re also looking into the possibility of technology that can transmit the current wirelessly, so the charge generated by your footsteps could power your Bluetooth headphones.

It may be a while, of course, before we see this technology in our own devices, but if it does hit, it will finally give us a way of repurposing the huge amounts of energy our bodies currently lose when we move around, walk, and even just make gestures with our hands.

“What if you could take the mechanical energy from swiping pages on your tablet and use that to charge the battery of the device itself?” Sepulveda told Tracy Staedter at Seeker.

“That could reduce the time required to recharge your device.”

Watch the video. URL:https://youtu.be/_-kkkNdbils

Power from the sea?


Triboelectric nanogenerator extracts energy from ocean waves.

As sources of renewable energy, sun and wind have one major disadvantage: it isn’t always sunny or windy. Waves in the ocean, on the other hand, are never still. American researchers are now aiming to use waves to produce energy by making use of contact electrification between a patterned plastic nanoarray and water. In the journal Angewandte Chemie, they have introduced an inexpensive and simple prototype of a triboelectric nanogenerator that could be used to produce energy and as a chemical or temperature sensor.

Power from the sea? Triboelectric nanogenerator extracts energy from ocean waves

The triboelectric effect is the build up of an electric charge between two materials through contact and separation – it is commonly experienced when removal of a shirt, especially in dry air, results in crackling. Zhong Lin Wang and a team at the Georgia Institute of Technology in Atlanta have previously developed a triboelectric generator based on two solids that produces enough power to charge a mobile telephone battery. However, high humidity interferes with its operation. How could this technology work with waves in water? The triboelectric effect is not limited to solids; it can also occur with liquids. The only requirement is that specific electronic levels of two substances are close enough together. Water just needs the right partner – maybe a suitable plastic.

As a prototype, the researchers made an insulated plastic tank, whose lid and bottom contain copper foil electrodes. Their system is successful because the inside of the lid is coated with a layer of polydimethylsiloxane (PDMS) patterned with tiny nanoscale pyramids. The tank is filled with deionized water. When the lid is lowered so that the PDMS nanopyramids come into contact with the water, groups of atoms in the PDMS become ionized and negatively charged. A corresponding positively charged layer forms on the surface of the water. The electric charges are maintained when the PDMS layer is lifted out of the water. This produces a potential difference between the PDMS and the water. Hydrophobic PDMS was chosen in order to minimize the amount of water clinging to the surface; the pyramid shapes allow the water to drop off readily. Periodic raising and lowering of the lid while the electrodes are connected to a rectifier and capacitor produces a direct current that can be used to light an array of 60 LEDs. In tests with salt water, the generator produced a lower output, but it could in principle operate with seawater.

The current produced decreases significantly as temperature increases, which could allow this device to be used as a . It also decreases when ethanol is added to the , which suggests potential use of the system as a chemical sensor. By attaching probe molecules with specific binding partners, it may be possible to design sensors for biomolecules.