New method of making nanobatteries

A University of Tulsa chemistry professor, Dale Teeters and two former students, Nina Korzhova and Lane Fisher have been awarded a patent for a method of making nanobatteries for use in tiny machines similar to the microbe-size craft that travelled through a human's blood vessels in the 1966 science-fiction movie, 'Fantastic Voyage'.

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-storey 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 flash light batteries placed side by side."

The method includes use of porous membrane, filling 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 aluminium sheet that is placed in acid solution under an electric current, resulting in an aluminium 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 V. 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 nm 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.