SPECIAL FEATURE: EMERGING TECHNOLOGIES
Development of a paper-thin battery was accomplished by infusing paper with carbon nanotubes, which consist of carbon atoms wrapped in tubes that measure a few billionths of a meter.
Toss a paper airplane, and, for a few entertaining seconds, there is the illusion of flight. But in the not-so-distant future, flying paper could cease to be illusory, thanks to a new electrical component made almost entirely of paper. The component can function as a battery, a supercapacitor, or a hybrid of both. Researchers anticipate a wide variety of applications for the component, including a number of novel possibilities related to medical devices, according to findings published in the August 13 issue of the Proceedings of the National Academy of Sciences.
Development of the component entailed infusing paper with carbon nanotubes, which consist of carbon atoms wrapped in tubes that measure only a few billionths of a meter. Cellulose—the plant seeds used in most kinds of paper—makes up 90% of the battery. The carbon atoms act as electrodes, allowing the battery to conduct electricity, and the battery is charged through contact with electrolytes. “We're not putting pieces together—it's a single, integrated device,” says Robert Linhardt, professor of biocatalysis and metabolic engineering at the Rensselaer Polytechnic Institute (Troy, NY) and member of the research team. “The components are molecularly attached to each other. The carbon nanotube print is embedded in the paper, and the electrolyte is soaked into the paper. The end result is a device that looks, feels, and weighs the same as paper.”
Lindhardt says the battery could also be powered through naturally occurring electrolytes, including those found in sweat, urine, and blood. The availability of batteries that can be charged by body fluids could stand to benefit the next generation of medical implants. Pacemakers are an example of implantable devices that both run on battery power and require an invasive procedure to change the battery. In the future, says Lindhardt, a pacemaker incorporating the paper-thin battery could charge itself inside of the human body simply by coming in contact with blood. The component’s ability to work within a wide temperature range—up to 150°C—coupled with the nontoxic nature of paper, further establish the component as a viable option for future implantable devices.
Due to its size—approximately that of a postage stamp—the component may retain significant advantages over batteries used in current implantable devices, even in cases in which recharging must occur outside of the body. “A battery this size would only need to go just below the surface of the skin to be installed into an implantable device,” says Lindhardt. “This could reduce the invasiveness of the procedure for replacing batteries.”
In most electrical systems, batteries and supercapacitors are separate components—not so with the paper-thin electrical component.
Defibrillators are an example of a medical application that would involve using the component as a supercapacitor. Today, defibrillators are bulky machines comprised of multiple components (including a supercapacitor), and defibrillation requires assistance by healthcare administrators. In the future, the entire unit could be something people carry in their pockets, and in case of emergency, use themselves.
“The entire defibrillator could be the size of a piece of paper,” Lindhardt explains. “You would take it out, unfold it, lay it on the patient’s chest, and the paper-thin supercapacitor would use its stored electrical energy to release a short, powerful burst in order to resuscitate the heart.”
Commercialization of the component may not be on the immediate horizon, but the research team has already turned its attention to the main impediment to achieving this goal. “We need a way to inexpensively mass-produce it,” Lindhardt says. “Once we get it down, we’ll have the ability to actually print batteries and supercapacitors using a roll-to-roll system similar to how newspapers are printed.”
Rensselaer Polytechnic Institute, Troy, NY