collapsing backpack charges gadgets as you walk - lithium ion polymer battery
MacGregor Campbell's wearable computers are on the way and soon you can power them yourself.
A new type of Nano
The generator converts the action in the walk into electricity to keep your gadgets running.
Wearable generators usually use induction, which is highly efficient, but requires a magnet of large size and heavy weight.
Smaller, lighter piezoelectric generators use ceramic crystals to convert pressure to voltage, but are expensive and much less efficient.
Now King Zhong of Georgia Tech in Atlanta and his colleagues have captured the electricity generated by touching two different charged surfaces and then separating them.
This is the so-called friction electric effect, which is the process of generating electrostatic shock.
Starting electricity with friction Nanogenerators (TENGs)
Create a force
Generating the backpack, the team coated one side of the plastic card with aluminum film filled with Nanoscale pores.
On the other side is a copper film with a series of polymer nano wires on the surface.
Then they put the card in a diamond box like a foldable carton (see diagram).
Every step you take lets the box fold itself so that both sides of the card come into contact.
The nano wires and holes are interlocked, increasing the contact area and increasing the amount of charge accordingly.
After each fold, the spring makes the sides jump back into shape, separates the cards and generates a potential difference, driving the current through the circuit.
Tencent's efficiency is about 50 compared to a very difficult piezoelectric system.
In the test, the 2 kg backpack generates more than 1 watt of power during walking, enough to run 40 LEDs at the same time (ACS Nano, doi. org/qhz).
The existing induction-based backpack generator can generate 5 to 20 watts of electricity, but the weight is 10 times the original.
The 2 kg backpack generates 1 watt of power during walking, enough power to run 40 miles. A separate experiment uses the same method to charge lithium. ion battery (ACS Nano, doi. org/qhzqhx).
Mr. Wang envisioned that Tencent could directly build sensors, mobile phones and wearable computers.
His team recently set up a booth.
A separate generator capable of powering a smartphone.
This article is in the title "battery-in-a-