Microscopic "Trampolines" Provide Novel Method To Study New Materials, Lucent Researchers Report

"This allows us to do experiments that couldn't be done before," says physicist David Bishop at Bell Labs, which is Lucent's research and development arm. "And when we learn about new materials, it can lead to better technology."

The researchers designed a silicon-based trampoline, whose top part, or "net," is a 300 micron-by-300 micron square -- roughly three times the width of a human hair. Each of the net's four corners is supported by a spring that's two microns wide and 100 microns long.

The trampoline belongs to a new, rapidly developing class of devices known as micro-electro mechanical systems (MEMS), which are used in various industrial applications. For instance, MEMS air-bag sensors and pressure sensors are widely used in automobiles.

In the experiment, the researchers glued a microscopic chunk of a superconducting sample, BEDT, onto the trampoline. Although the technique would work with a wide range of superconducting and non-superconducting materials, the researchers selected BEDT because its properties were well known. In addition, superconductors are inherently important materials because they lose all electrical resistance at low temperatures. Potential applications for superconductivity include transmitting power more efficiently over superconducting power lines and building very high-speed electronic circuits.

Bishop and his colleagues exposed the BEDT to a magnetic field that's roughly one million times more intense than the earth's, but lasts for only one hundredth of a second. The force of the magnetic field caused the BEDT to move as it became magnetized, similar to when a piece of metal exhibits magnetic properties when exposed to a strong magnet. As the trampoline's net bobbed up and down, the researchers were able to determine BEDT's magnetic properties, which are an important clue for researchers when studying why only certain materials exhibit superconducting qualities.

"This is the first time," said physicist Vladimir Aksyuk, "that a MEMS device has been used to measure the magnetization of such a small amount of material in a high-strength magnetic field in an extremely short time period."

Until the MEMS trampolines were developed, researchers were unable to accurately measure the magnetization of important materials in very large magnetic fields. Other techniques either were too insensitive or failed as the environment became increasingly hostile.