February 27, 2013
The world’s biggest tech companies all suddenly seem bent on one goal: claiming control of the screens and computers they think we’ll be wearing in the near future. Google has recently made waves by recruiting “explorers” to try out its new glasses-mounted smartphone technology (aptly called “Google Glass”), while Apple’s recent patent for a curved glass computerized watch garnered widespread attention in tech circles.
Many, though, have noted that one of the biggest limitations for wearable tech is durability—it’s difficult to build a tiny, powerful computer capable of withstanding the rigors imposed by daily wear.
Part of that longstanding problem could be solved by a technology announced yesterday in the journal Nature Communications: a thin, stretchable, flexible battery that can provide power while being pulled out to 300 percent of its original size, and then shrink back without any damage. The device, developed by a team of researchers from the University of Illinois, Northwestern and elsewhere, could fill a crucial gap as engineers try to move our computers from rigid phones and tablets to flexible platforms.
The device relies upon a process that the researchers call “ordered unraveling.” Its energy-storing components (small lithium-ion batteries) are printed on a stretchy polymer, connected by long, S-shaped wires. When the polymer is pulled, the wires act like springs, stretching out to cover more distance until they become fully taught.
“When we stretch the battery, the wavy interconnecting lines unfurl, much like yarn unspooling. And we can stretch the device a great deal and still have a working battery,” Yonggang Huang, an engineer at Northwestern and one of the paper’s co-authors, said in a statement.
Many of the researchers involved have worked on various components of flexible electronics previously, including a specialized heart surgery tool that involves sensors and instruments printed on a stretchable balloon catheter. This device, though, represents the first time they’ve figured out how to apply the same principles of stretchiness to batteries in particular.
As a proof of principle, the device is very promising: It’s extremely durable, and still works even as it’s stretched and twisted. Moreover, the researchers say that the design could incorporate the ability to be charged wirelessly, with inductive coils that merely need to be in contact with a power supply rather than having to be plugged in, like commercially-available charging mats.
Currently, though, prototype provides far too little power to be useful for computing—it’s only able to power a small LED for 8-9 hours before needing a recharge—and can only go through 20 cycles of recharging before beginning to lose total capacity. But before degrading, at least, the amount of power is comparable to that of a conventional lithium-ion battery (the type used in most electronics) of a similar size, and the concepts employed should be able to perform similarly at a larger scale.
“The most important applications will be those that involve devices integrated with the outside of the body, on the skin, for health, wellness and performance monitoring,” John Rogers of the University of Illinois, another co-author, told the BBC. At this point, it’s hard to fully imagine the complete range of potential devices that could make use of the technology—it could be incorporated into anything from bendable smartphone watches to biological implants like pacemakers.
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