On-chip battery debuts

Researchers from Hosei University in Japan have taken a big step toward giving nano devices and biochips onboard power supplies.

The researchers etched 200- by 100- by 2-micron trenches into silicon chips to house tiny batteries. A micron is one thousandth of a millimeter, and human hair is about 75 microns in diameter.

The researchers filled the trenches with a porous glass electrolyte and electrodes made from lithium and lithium manganese oxide. The battery produces a current of electrons when lithium ions move through the glass from one electrode to the other. The researchers added numerous nano-sized pores to the inside and surface of the glass, which opened more paths for the lithium ions to travel, increasing the tiny battery's power. A nanometer is one thousandth of a micron.

The 3.6-volt batteries deliver 34.6 watt hours per square centimeter.

The researchers are working on embedding larger numbers of smaller batteries into silicon chips, and are working on materials that allow ions to diffuse more efficiently. Practical miniature batteries could be ready for use in computer chips and biochips in five to ten years, according to the researchers.

The work appeared in the December 23, 2002 issue of Applied Physics Letters.