The smallest of computers must rely on ultrasound or photovoltaic cells to fill small batteries with energy from vibrations or sunlight, with little space for storage.
This has its downsides, because the computer will not work without a constant power source or in dark places like the human body.
So some scientists in Europe are proposing an alternative structure: a small battery that relies on folding tiny nano-thin layers like origami. The battery is only a prototype at the moment, but the initial results are encouraging.
"There is an urgent need to develop high-performance batteries for millimeter and sub-millimeter system, because such energy storage systems will facilitate the development of truly independent microsystems," the researchers wrote.
Full-size computer batteries typically rely on "wet chemistry," which means metallic foils that conduct electricity are put in contact with liquid electrolytes to generate a flow of energy. However, chip-based batteries of a certain scale cannot support liquid electrolytes.
In this way, the inventors of this new small battery squeezed a solid electrolyte between two tiny strips coated with an extremely thin film of electrodes, one positive and one negative.
However, this solid electrolyte is not quite as efficient as using a liquid electrolyte, which is where the folding comes in. By wrapping a flat battery assembly in a "Swiss cylinder", scientists can compress much more space into a tight space. This is how the cylinder cells in Tesla electric cars work.
At the cubic millimeter scale, it is very difficult to roll thin and brittle materials into this kind of shape by external pressure.
Fortunately, there is another way to make the material fold on its own, and it's called "little origami."
And the technique works like a roller blind. And when the thinner material is pulled down, you let go of this mechanical tension, and everything will curl up and roll into a cylinder.
On a slide, the researchers were able to achieve this motion by clamping one side of the thin material to create, in essence, a window-curtain strip.
In the end, the team was able to assemble a prototype of the small battery in an area of just 0.04 square millimeters, providing eight times higher capacity than a flat battery of a similar size could achieve.
The researchers say the cylinder resembles the standard structure of the Swiss coil used in larger batteries, including at least two layers of the collector, an anode tape, and an electrolyte film wrapped together.
Not only is the design rechargeable, the researchers say, but the battery in its current state can power our smallest computers for about 10 hours. There is still more work to be done.
Source: Al-Mayadeen
