Patent Awarded for Method of Making Nanobatteries
A University of Tulsa chemistry professor and two former students have been awarded a patent for a method of making nanobatteries for use in tiny machines similar to the microbe-size craft that traveled through a human's blood vessels in the 1966 science-fiction movie, "Fantastic Voyage."
U.S. Patent 6,586,133 was awarded July 1, 2003, to chemistry professor Dale Teeters and to Nina Korzhova and Lane Fisher, who were both chemical engineering students at TU when they worked on the process to manufacture nanoscale microscopic batteries. One nanometer is one-billionth of a meter. The diameter of an average hair is 50,000 nanometers.
So far Teeters and his researchers have made batteries that are so small that more than 40 could be stacked across the width of a hair -- and they continue to make even smaller batteries.
The invention is a manufacturing process that can build, charge and test nanobatteries.
Through nanotechnology, objects are built in a way that nearly each atom is precisely placed the way each brick might be laid when constructing a 10-story building.
The process could be compared to making a layered cake. If the finished product were enlarged, says Teeters, "it would look like a tray of flashlight batteries placed side by side."
Funding for the research in the amount of $446,559 was sponsored by the Department of the Navy's Office of Naval Research and the Oklahoma State Regents for Higher Education. The method includes use of a porous membrane, filling the pores with an electrolyte, and capping the pores with electrodes. Conventional batteries have two electrodes that deliver the charge and an electrolyte through which charged ions move.
The manufacturing process begins with an aluminum sheet that is placed in acid solution under an electric current, resulting in an aluminum oxide membrane. When the metal is dissolved, a honeycomb structure results. The pores are then filled with an electrolyte -- comparable to the liquid in a car battery -- which in this case, is a plastic-like polymer. Next the filled pores are capped on both sides with electrodes -- ceramic or carbon particles -- similar in function to a car battery's lead plates and two posts.
Key tools in the process are a scanning electron microscope and an atomic force microscope, which can observe and manipulate particles as small as molecules -- and is used to charge the microscopic array of batteries. Each battery packs as much as 3.5 volts. The microscope's custom-made electrically-conducting cantilever tip is touched to the electrode so that the battery can be charged and tested.
The atomic force microscope senses the force exerted by the surface of a solid on its probe tip -- similar in appearance to a record player needle. The tip itself is so small, perhaps 20 nanometers wide, that it can't be seen with a regular light microscope.
"Materials exert a mutual attraction when the distance between them approaches the atomic scale," explains Teeters. When the probe is scanned at a constant height across a surface, it senses an attractive force that rises and falls according to the topography. A computer displays the shape of the scanned surface. For instance, an image of a layer of mica looks like the checkerboard pattern of a tweed coat. The "bumps" in the material are single atoms of oxygen. This type of instrument is essential to work with these nanobatteries that Teeters and his students have developed.
At an international conference of the Electrochemical Society in Paris in May, officials with electronics giants Sanyo and Panasonic talked to Teeters with interest regarding the battery-making process.
As computer, medical and other devices become smaller, Teeters says, smaller storage batteries are needed to power these robotic creations, sometimes called MEMS, or microelectromechanical systems.
Amazingly, Teeters says, the science fiction theme in "Fantastic Voyage" has proven to be a fact: A German company has created a "submarine" tiny enough that it could be injected into an artery and directed to release a medication in a specific part of the body. "But to get anywhere, it needs a power supply."
Teeters says Fisher worked on creating the electrode particles, and Korzhova's job was to place the electrolyte in the pores and charge the batteries. "The result is that we came up with an innovative technique to shrink batteries down to this incredibly small scale."
Illustrations and text pertaining to the patent can be seen at http://www.uspto.gov/
The process is also described in the June 2003 issue of the Journal of Power Sources, "Vanadia xerogel nanocathodes used in lithium microbatteries," by TU student Christina Dewan and Dale Teeters, a paper presented at the 11th International Meeting on Lithium Batteries.