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Posted: Feb 07, 2014

Origami batteries for deformable electronics (w/video)

(Nanowerk Spotlight) In order to get electronics out of their rigid casings and integrated into flexible materials like textiles or even stretchable biomedical devices that interface directly with organs such as the skin, heart and brain, researchers have come up with solutions ranging from hydrogel electrodes in dielectric elastomers and super-stretchy supercapacitors to stretchable supercapacitors using buckled carbon nanotube (CNT) macrofilms, carbon nanotube-coated cotton yarns and CNT-coated sponges.
In order to fabricate entirely flexible electronic devices, the components that power them – such as batteries – not only need to be fully flexible as well but they have to be compatible with commercially available manufacturing technologies. This would require achieving a high degree of deformability without using elastomeric materials.
For batteries, this task is even more challenging as safety considerations need to be taken into account.
In a previous Nanowerk Spotlight we reported on lithium-ion (Li-ion) batteries that can be folded using the Miura-ori pattern – a folding pattern that has been used to fold maps.
The same team from Arizona State University, led by associate professor Hanqing Jiang and assistant professors Hongyu Yu and Candace K. Chan, has now published a report in Nature Communications ("Origami lithium-ion batteries") that demonstrates the fabrication of a highly deformable lithium-ion battery using standard electrodes and commercially standard packaging technologies.
The origami design concept enables Li-ion batteries with unprecedented mechanical deformability including folding, unfolding, twisting and bending.
Dynamic deformation of an origami lithium-ion battery using 90 Miura folding connected to a voltmeter.
"Our previous work of using folding to improve the energy density helped us to implement some of the recent experiments, such as using nanotube ink to maintain the electrical conductivity after folding," Jiang tells Nanowerk.
The researchers borrowed the idea for their foldable battery from origami. One of main characteristics of origami is compactness and deformability of the folded structures. Here, for example, the team used the Miura technique, which is a rigid origami folding pattern.
"The deformability, particularly the stretchability of this pattern is achieved by the folding and unfolding of the creases while maintaining the paper rigid. This is ideal to develop highly deformable electronics and motivates us to conduct this work," Jiang explains.
Thanks to using the origami concept, the researchers were able to achieve significant system-level linear and areal deformability for their battery (over 1,000%), large twistability and bendability, and up to 74% areal coverage.
Moreover, this origami lithium ion battery uses commercially standard materials and packaging technologies.
"This work represents the fusion of the art of origami, materials science, and functional energy storage devices, and could provide a paradigm shift for architecture and design of flexible and curvilinear electronics with exceptional mechanical characteristics and functionalities," says Jiang.
According to the team, this origami battery can be incorporated with other deformable electronics components by two means.
The first approach is to build a functional system that may include energy harvesting devices (e.g., solar cells), energy storage devices (e.g., Li-ion batteries) and other devices (e.g., sensor arrays and microprocessors) in the same origami platform to achieve a highly deformable system.
The second approach is to build a stand-alone Li-ion battery by encapsulating the origami battery with elastomeric materials and then integrating with other functional devices.
Going forward, the team's plan is to develop a highly deformable system with all necessary components – including energy harvesting, energy storage, sensors, processors, wireless communications, etc, using the concept of origami.
"We are on track to developing such a system," says Jiang. "For instance, led by associate professor Yong Xu, we have published a paper ("A robust polymer microcable structure for flexible devices") for locking an origami structure using phase change materials; and in an upcoming paper (Applied Physics Letters, in press) we describe the fabrication of origami-enabled deformable silicon solar cells."
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