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Jan. 24, 2005 — In more ways than one, it’s a delicate balancing act that mPhase Technologies Inc. wants to execute.
First is the company’s technology: making a nanobattery by placing droplets of water on filaments of silicon. A jolt of electricity then bursts the droplet, it soaks the silicon, and pent-up energy is released.
Then there is the company itself. Eight years old, mPhase was founded to sell telecommunications components. Leveraging that business to leap into the uncertain world of nanotechnology is quite a jump.
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“Frankly, it’s really a branch into a new field,” admitted Steve Simon, mPhase’s vice president of engineering.
Nobody scoffs at the goal. Working in partnership with Bell Labs, mPhase has demonstrated a proof-of-concept nanobattery crammed with filaments of silicon “nanograss” only a few hundred microns high and is working on a prototype that can illuminate a light-emitting diode. On Dec. 16, it reported that the military, oil industry and homeland defense expressed interest in using its nanobatteries to power sensors.
mPhase launched in 1996 as a maker of components and software for DSL service or other telecommunications lines, with a particular eye towards video to the home. It went public in 1997, trading under the ticker symbol XDSL. Although headquartered in Norwalk, Conn., the company had engineering labs in New Jersey, home to Lucent’s fabled Bell Labs. The two companies agreed in 2004 to work together on energy technology created at Bell Labs.
“The idea was to take stuff in the lab that was going nowhere from a commercial point of view, and focus it on a particular technology,” Simon said. “We chose the battery technology.”
The underpinning of the battery is the nanograss developed by Bell Labs scientists. Using standard lithography techniques, researchers carve silicon filaments several hundred microns high and 300 nanometers in diameter. The filaments are coated with water-repellent materials, so that droplets of liquid balance atop the nanograss but never touch them.
The droplets are electrolytes, brimming with ions. A jolt of heat or electricity then bursts the droplets; they spill onto the nanograss, the ions generate power, and the filaments carry the electricity to whatever device is attached.
The challenge, Simon said, is to tweak the mixture of coatings and droplets to ensure the largest “contact angle” — that is, to ensure the droplet soaks as much of the silicon as possible so it will generate the most power with the least stimulation.
Forging the correct nanostructures is one part of the process, “but the other part is getting the surface property correct,” said Tom Krupenkin, a Bell Labs researcher working on the battery. “If you change one part of it, that changes the whole picture.”
Bell Labs had been investigating the idea of a microscale chemical reactor for several years, Krupenkin said, but applications for a reactor proved elusive. Eventually, researchers thought of a battery: easy-to-understand, with well-known chemical properties.
At such small scale, mPhase’s batteries have several advantages, Simon said. Because the electrolyte is so close to the electrode (the silicon), they generate power faster than normal batteries; yet because the two surfaces never touch until activation, they should never corrode. Simon believes the nanobatteries’ lifespan is at least 20 years.
Initial batteries are a centimeter square and 800 microns high, each called a “cell.” Simon and Krupenkin want to stack the cells to power larger devices, and in theory they could be built directly into silicon devices such as RFID tags. What the batteries might ultimately cost, and how much power they could generate, remains to be seen.
Nanobatteries are a hot topic of research, although most work happens in academic or corporate labs. Dale Teeters, a University of Tulsa chemistry professor who studies nanobatteries, said a primary goal is to export the increased efficiency of nanobatteries to regular batteries, usually by building ever-smaller components. Exploiting nanoscale chemistry to create battery-like functions, as mPhase is trying to do, is a more exotic approach.
“It’s almost always about having nanoscale components,” said Teeters, who was not familiar with mPhase’s specific work. He has created batteries with components down to 200 nanometers, although he needs atomic force microscopes to charge it.
“It seems more and more people are working on nanobatteries, however you define it,” Teeters said.