Sugar-powered biobattery has 10 times the energy storage of lithium: Your smartphone might soon run on enzymes

Sugar-powered biobattery has 10 times the energy storage of lithium: Your smartphone might soon run on enzymes

  7:33:00 PM    Science Lover

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As you probably know, from sucking down cans of Coke and masticating on candy, sugar — glucose, fructose, sucrose, dextrose — is an excellent source of energy. Biologically speaking, sugar molecules are energy-dense, easy to transport, and cheap to digest. There is a reason why almost every living cell on Earth generates its energy (ATP) from glucose. Now, researchers at Virginia Tech have successfully created a sugar-powered fuel cell that has an energy storage density of 596 amp-hours per kilo — or “one order of magnitude” higher than lithium-ion batteries. This fuel cell is refillable with a solution of maltodextrin, and its only by products are electricity and water. The chief researcher, Y.H. Percival Zhang, says the tech could be commercialized in as soon as three years.

Now, it’s not exactly news that sugar is an excellent energy source. As a culture we’ve probably known about it since before we were Homo sapiens. The problem is, unless you’re a living organism or some kind of incendiary device, extracting that energy is difficult. In nature, an enzymatic pathway is used — a production line of tailor-made enzymes that meddle with the glucose molecules until they become ATP. Because it’s easy enough to produce enzymes in large quantities, researchers have tried to create fuel cells that use artificial “metabolism” to break down glucose into electricity (biobatteries), but it has historically proven very hard to find the right pathway for maximum efficiency and to keep the enzymes in the right place over a long period of time.

A diagram of the enzymatic fuel cell. The little Pac-Man things are enzymes.

Now, however, Zhang and friends at Virginia Tech appear to have built a high-density fuel cell that uses an enzymatic pathway to create a lot of electricity from glucose. There doesn’t seem to be much information on how stable this biobattery is over multiple refills, but if Zhang thinks it could be commercialized in three years, that’s a very good sign. Curiously, the research paper says that the enzymes are non-immobilized — meaning Zhang found a certain battery chemistry that doesn’t require the enzymes to be kept in place… or, alternatively, that it will only work for a very short time.

The Virginia Tech biobattery uses 13 enzymes, plus air (it’s an air-breathing biobattery), to produce nearly 24 electrons from a single glucose unit. This equates to a power output of 0.8 mW/cm, current density of 6 mA/cm, and energy storage density of 596 Ah/kg. This last figure is impressive, at roughly 10 times the energy density of the lithium-ion batteries in your mobile devices. [Research paper: doi:10.1038/ncomms4026 - "A high-energy-density sugar biobattery based on a synthetic enzymatic pathway"]

If Zhang’s biobatteries pan out, you might soon be recharging your smartphone by pouring in a solution of 15% maltodextrin. That battery would not only be very safe (it produces water and electricity), but very cheap to run and very green. This seems to fit in perfectly with Zhang’s homepage, which talks about how his main goals in life are replacing crude oil with sugar, and feeding the world.

The other area in which biobatteries might be useful is powering implanted devices, such as pacemakers — or, in the future, subcutaneous sensors and computers. Such a biobattery could feed on the glucose in your bloodstream, providing an endless supply of safe electricity for the myriad implants that futuristic technocrats will surely have. 

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A Battery Made of Wood?

A Battery Made of Wood?

  9:04:00 AM    Science Lover

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A sliver of wood coated with tin could make a tiny, long-lasting, efficient and environmentally friendly battery.

Close-up image of wood fibers. "Wood fibers that make up a tree once held mineral-rich water, and so are ideal for storing liquid electrolytes, making them not only the base but an active part of the battery," Liangbing Hu said. (Credit: Image courtesy of University of Maryland)

But don't try it at home yet -- the components in the battery tested by scientists at the University of Maryland are a thousand times thinner than a piece of paper. Using sodium instead of lithium, as many rechargeable batteries do, makes the battery environmentally benign. Sodium doesn't store energy as efficiently as lithium, so you won't see this battery in your cell phone -- instead, its low cost and common materials would make it ideal to store huge amounts of energy at once, such as solar energy at a power plant.

Existing batteries are often created on stiff bases, which are too brittle to withstand the swelling and shrinking that happens as electrons are stored in and used up from the battery. Liangbing Hu, Teng Li and their team found that wood fibers are supple enough to let their sodium-ion battery last more than 400 charging cycles, which puts it among the longest lasting nanobatteries.

"The inspiration behind the idea comes from the trees," said Hu, an assistant professor of materials science. "Wood fibers that make up a tree once held mineral-rich water, and so are ideal for storing liquid electrolytes, making them not only the base but an active part of the battery."

Lead author Hongli Zhu and other team members noticed that after charging and discharging the battery hundreds of times, the wood ended up wrinkled but intact. Computer models showed that that the wrinkles effectively relax the stress in the battery during charging and recharging, so that the battery can survive many cycles.

"Pushing sodium ions through tin anodes often weaken the tin's connection to its base material," said Li, an associate professor of mechanical engineering. "But the wood fibers are soft enough to serve as a mechanical buffer, and thus can accommodate tin's changes. This is the key to our long-lasting sodium-ion batteries."

The team's research was supported by the University of Maryland and the U.S. National Science Foundation.

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Soft Memory Device Opens Door to New Biocompatible Electronics

Soft Memory Device Opens Door to New Biocompatible Electronics

  12:47:00 AM    Science Lover

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Researchers from North Carolina State University have developed a memory device that is soft and functions well in wet environments -- opening the door to a new generation of biocompatible electronic devices.

Researchers have created a memory device with the 
physical properties of Jell-O, and that functions well 
in wet environments. (Credit: Michael Dickey, North 
Carolina State University)

"We've created a memory device with the physical properties of Jell-O," says Dr. Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State and co-author of a paper describing the research.

Conventional electronics are typically made of rigid, brittle materials and don't function well in a wet environment. "Our memory device is soft and pliable, and functions extremely well in wet environments -- similar to the human brain," Dickey says.

Prototypes of the device have not yet been optimized to hold significant amounts of memory, but work well in environments that would be hostile to traditional electronics. The devices are made using a liquid alloy of gallium and indium metals set into water-based gels, similar to gels used in biological research.

The device's ability to function in wet environments, and the biocompatibility of the gels, mean that this technology holds promise for interfacing electronics with biological systems -- such as cells, enzymes or tissue. "These properties may be used for biological sensors or for medical monitoring," Dickey says.



The device functions much like so-called "memristors," which are vaunted as a possible next-generation memory technology. The individual components of the "mushy" memory device have two states: one that conducts electricity and one that does not. These two states can be used to represent the 1s and 0s used in binary language. Most conventional electronics use electrons to create these 1s and 0s in computer chips. The mushy memory device uses charged molecules called ions to do the same thing.

In each of the memory device's circuits, the metal alloy is the circuit's electrode and sits on either side of a conductive piece of gel. When the alloy electrode is exposed to a positive charge it creates an oxidized skin that makes it resistive to electricity. We'll call that the 0. When the electrode is exposed to a negative charge, the oxidized skin disappears, and it becomes conducive to electricity. We'll call that the 1.

Normally, whenever a negative charge is applied to one side of the electrode, the positive charge would move to the other side and create another oxidized skin -- meaning the electrode would always be resistive. To solve that problem, the researchers "doped" one side of the gel slab with a polymer that prevents the formation of a stable oxidized skin. That way one electrode is always conducive -- giving the device the 1s and 0s it needs for electronic memory.

The paper was published online July 4 by Advanced Materials. The paper was co-authored by NC State Ph.D. students Hyung-Jun Koo and Ju-Hee So, and NC State INVISTA Professor of Chemical and Biomolecular Engineering Orlin Velev. The research was supported by the National Science Foundation and the U.S. Department of Energy.

NC State's Department of Chemical and Biomolecular Engineering is part of the university's College of Engineering.

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Glitter-Sized Solar Photovoltaics Could Revolutionize the Way Solar Energy Is Collected and Used

Glitter-Sized Solar Photovoltaics Could Revolutionize the Way Solar Energy Is Collected and Used

  1:21:00 AM    Science Lover

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Sandia National Laboratories scientists have developed tiny glitter-sized photovoltaic cells that could revolutionize the way solar energy is collected and used.

Representative thin crystalline-silicon photovoltaic cells -- these are from 14 to 20 micrometers thick and 0.25 to 1 millimeter across. (Credit: Image by Murat Okandan)

The tiny cells could turn a person into a walking solar battery charger if they were fastened to flexible substrates molded around unusual shapes, such as clothing.

The solar particles, fabricated of crystalline silicon, hold the potential for a variety of new applications. They are expected eventually to be less expensive and have greater efficiencies than current photovoltaic collectors that are pieced together with 6-inch- square solar wafers.

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