Tiny batteries power the miniaturization of computers

Using tiny batteries, researchers hope to power ever-smaller computers and advance the Internet of Things and pervasive computing.

There was a time when the most advanced computers in the world took up entire rooms. Now we carry smart phones and other electronic devices in our pockets.

“The rate of miniaturization [for computers] is about 100 times per decade,” write a team of experts led by Oliver Schmidt of Chemnitz University of Technology, Germany. “Advances in microelectronics have allowed the use of miniaturized computers […] the size of a dust particle less than a square millimeter in diameter and a few hundred micrometers thick, creating an environment for ubiquitous computing.

The idea of ​​pervasive or pervasive computing is quite exciting. It is a burgeoning concept in software engineering in which microprocessors are embedded in everyday objects to allow them to perform different tasks. This will have many implications for the advancement of the Internet of Things, miniaturized medical implants, microrobotic systems and ultra-flexible electronics.

But the field encounters a problem because there is a disconnect between these tiny computers and the availability of batteries small enough to fit inside and power them. The key is the development of sub-millimeter scale energy harvesters and storage devices – a problem that researchers around the world, including Schmidt, are working on..

Conventional large-scale batteries are difficult to miniaturize because they are based on “wet chemistry”, where electrodes, electrolytes and additives are usually processed into a slurry and coated onto a sheet of metal. It’s possible to create microbatteries this way, the researchers say, and there are examples with decent energy and power density, but they can’t be small enough because, at some scale, liquid electrolytes are only simply not feasible.

One solution could be solid-state batteries that sit on stacked layers of thin films. In 2019, Schmidt and his colleagues set out to develop the world’s smallest battery using a layered system in which a solid-state electrolyte is installed between two thin-film electrodes.

Tiny batteries made using the “Swiss roll”

Since solid-state electrolytes are less efficient than their liquid counterparts, the team used a micro-origami technique called a “Swiss roll” to reduce the battery’s size while increasing its power – a similar process. to that used by Tesla for the batteries of its electric cars.

Realizing the design of the Swiss roll on a chip through microfabrication processes is extremely difficult, however, the use of on-chip self-assembly made by micro-origami allowed the team to achieve their goal, resulting in a cylindrical battery with a surface area of ​​0.04 square millimeters and with eight times the capacity of a flat battery of similar size.

The idea is based on the tension inherent in the system, which results in an automatic return to itself. By layering consecutive layers of polymers, metals and dielectric materials (components of the battery) on a wafer chip surface, you can force an architecture that resembles the Swiss roll by fixing one side of the thin materials, then releasing the voltage.

“Thus, no external force is needed to create such a self-winding cylindrical micro-battery,” the team said in a statement. “The method is compatible with established chip fabrication technologies and is capable of producing high throughput micro-batteries on a wafer surface. “

The resulting rechargeable microbatteries could power tiny dust-sized computer chips for about ten hours. An exciting first step, but there is still work to be done. “There is still huge optimization potential for this technology, and we can expect much more powerful microbatteries in the future,” Schmidt said.

Reference: Fei Li, et al., Self-assembled flexiAsymmetric and integrable 3D microtubular supercapacitors, Advanced Science (2019). DOI: 10.1002/advs.201901051

Yang Li, et al., On-Chip Batteries for Dusty Computers, Advanced Energy Materials (2022). DOI: 10.1002/aenm.202103641

Image credit: Niek Doup Unsplash

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