When computers first appeared in the twentieth century, they needed very large rooms to accommodate. Decades have passed, computers have been shrinking in size, and what was once a behemoth is now packed into a variety of portable electronics. But for technology to evolve, they also need to become smaller.
Image credit: Wiley Online Library
Scientists at Chemnitz University of Technology recently successfully developed the world's smallest battery, the size of dust, but the inspiration for this technology is related to a common food - Swiss rolls.
Micro battery compared to the volume of a grain of salt, picture from: cnBeta
In fact, a few years ago, a computer with a volume of only 0.04 cubic millimeters appeared, but it could only be demonstrated in the laboratory. However, the size mismatch between microcells and microelectronics has become a fundamental obstacle to the development of miniature intelligent systems that require power anytime, anywhere, and existing technologies cannot shrink the footprint of the battery while maintaining sufficient energy storage.
Therefore, for dust-sized computers to operate permanently, the key is to develop sub-millimeter-scale energy harvesters and storage devices. Mimicking the manufacture of cylindrical batteries, researchers at Chemnitz University of Technology employ a self-assembling process in which stacked films are wound in a Swiss-rolled structure to reduce the footprint.
In the macro world, an effective way to increase the floor space capacity is to wrap flat batteries into Swiss coils. Tesla's electric car is to increase the footprint of the battery by about 28 times, and assemble 18650 batteries into a battery pack to provide power.
However, it is not easy to achieve this Swiss roll design on the chip by micromachining, because the thin and brittle layers wrapped with external forces on the chip can neither be used as a mass production process, nor can it achieve sufficient precision to achieve high yield and repeatability.
Therefore, the researchers folded or rolled the two-dimensional nanolayer into a microstructure to convert the film stack into a "micro Swiss roll" by folding or rolling it into a microstructure, which also solved the problem that small size area and high energy density are difficult to balance to some extent.
In addition, the core parameter that determines whether these dust-sized batteries can eventually be integrated into the microsystem is the energy density they can achieve. The researchers believe that a more practical use for miniature batteries is to provide energy as a backup power source in the event of an interruption in energy harvesting. This requires at least a few hours of energy. Therefore, their minimum energy density per square centimeter is 100 microwatt hours (μWh).
The researchers envision that microcells are suitable for eventual integration into tiny chips with circuitry that can be used in biocompatible sensors in humans, such as detecting recovery and organ condition after surgery.
Researchers, left: Zhu Minshen, right: Oliver G. Schmidt, image from cnBeta
Professor Oliver G. Schmidt, who led the study, said: "There is still great potential for optimization of this technology, and we can expect more powerful micro batteries in the future."
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