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Tiny battery could provide on-chip power

12 May 2015

Researchers combine 3D holographic lithography and 2D photolithography to produce a 3D micro-battery suitable for large-scale on-chip integration.

The holographically patterned microbattery (photo: University of Illinois)

"This 3D micro-battery has exceptional performance and scalability, and we think it will be of importance for many applications," says Professor Paul Braun of the University of Illinois at Urbana-Champaign where the work was carried out. "Micro-scale devices typically utilise power supplied off-chip because of difficulties in miniaturising energy storage technologies.

"A miniaturised high-energy and high-power on-chip battery would be highly desirable for applications including autonomous micro-scale actuators, distributed wireless sensors and transmitters, monitors, and portable and implantable medical devices," Braun adds.

Hailong Ning, a graduate student at Illinois and author of a paper on the work published in the Proceedings of the National Academy of Sciences, says that due to the complexity of 3D electrodes, it is generally difficult to realise such batteries, let alone the possibility of on-chip integration and scaling.

"In this project, we developed an effective method to make high-performance 3D lithium-ion micro-batteries using processes that are highly compatible with the fabrication of microelectronics," says Ning. "We utilised 3D holographic lithography to define the interior structure of electrodes and 2D photolithography to create the desired electrode shape." 

Enabled by a 3D holographic patterning technique - where multiple optical beams interfere inside the photoresist creating a desirable 3D structure - the battery possesses well-defined, periodically structured porous electrodes, that facilitates the fast transport of electrons and ions inside the battery, offering supercapacitor-like power.

"Although accurate control on the interfering optical beams is required to construct 3D holographic lithography, recent advances have significantly simplified the required optics, enabling creation of structures via a single incident beam and standard photoresist processing," says Professor John Rogers who worked with Braun's team. "This makes it highly scalable and compatible with micro-fabrication."

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