Embedding Microbatteries On-chip for Greater Miniaturization

October 05, 2021 by Darshil Patel

Researchers develop microbatteries that are as thick as three sheets of paper, and can be embedded into sensor circuitry.

High-performance miniaturized energy storage solutions have developed in recent years due to the explosive growth in wearable electronics and IoT. Apart from these growing sectors, portable and integrated microelectronics systems find applications in various modern devices such as medical implants, radiofrequency identifiers, NFCs or smart cards, and microsensor networks. These microsystems are powered by ultra-small batteries.

But as the systems shrink further, there is a need to provide high-performance energy-storage solutions on-chip to deliver energy at actual usage points and enhance the capabilities of miniature devices.

However, one of the major challenges for implementing microbatteries is related to the manufacturing process and compatibility with the integrated circuit technologies. The non-compatibility with conventional ICs is because rechargeable thin-film microbatteries use solid electrolytes. Moreover, present microbatteries face the challenge of low energy density and low power delivery. As a result, micro-sized batteries are currently commercialized by only a few brands in the electronics segment.

Kristofer Pister, a Professor in the Department of Electrical Engineering and Computer Science at the University of California Berkeley, leads the research on embedding microbatteries directly on sensor circuitry to build an on-chip power source. Integration of microbatteries on wafer allows for energy delivery at actual usage points. This advantage is critical for the high performance of microsystems.


Kristofer Pister, who leads the research on embedding microbatteries on-chip. Image Courtesy of Berkeley Research.


The microbatteries under development by the researchers have a high energy density, are lighter, and are cheaper to produce. The batteries share the same fabrication process as the printed electronic circuits. Moreover, the batteries are about the same thickness as three sheets of paper.

Pister explains how these batteries are realized, "The circuitry is stencil printed into cavities on the silicon wafer. You can picture it as etching micro-trenches into the wafer. It's the same principle as making screen-printed t-shirts. You have a pattern with holes in some areas and not in others. We deposit electrode slurries in the patterned cavities."


Microbattery fabricated on the backside of a silicon chip. Image Courtesy of Berkeley Research.


Pister notes that on-chip power sources would be useful in applications ranging from small implantable medical devices to large oil refineries. The researchers believe that their developed design will be a part of devices in the full range of commercial spaces.


About the Researchers

Kristofer Pister leads the research to embed microbatteries directly on-chip. Much of the work is also being done by his post-doc, Dr. Anju Toor, who has developed a battery design and fabrication process to print high-capacity batteries.

The work is supported by Bakar fellows Program.