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Published on July 11th, 2017 | By: Faye Oney

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Stronger, more conductive alloy could replace silicon in MEMS

Published on July 11th, 2017 | By: Faye Oney

[Image above] Credit: Ai.Comput’In; Flickr CC BY-NC-ND 2.0

 

 

The electronics industry has gotten a lot of mileage out of silicon

 

Silicon is used to make semiconductors in solid-state devices for the computer and electronics industries. Because it is widely available and inexpensive, silicon is almost exclusively used to make computer chips. And silicon is also used to make microscopic sensors called micro-electro-mechanical systems, or MEMS.

 

MEMS are tiny devices comprised of sensors, actuators, microelectronics, and microstructures. They’re used to convert energy from one form to another and are used in a variety of industries, including automotive, military, utilities, consumer electronics, medicine, and biotechnology.

 

Although silicon may appear to be a “wonder element,” it does have its limitations, especially as a component in the manufacture of MEMS. As technology gets more complicated, requiring more power for smaller devices that demand more energy, silicon won’t cut it anymore as a conducting material. At high temperatures, MEMS lose their strength and conducting ability, and, because it tends to be brittle, silicon—a major component of MEMS—can break easily.

 

Alternative materials for MEMS

 

Kevin J. Hemker, the Alonzo G. Decker Chair of Mechanical Engineering at the Whiting School of Engineering at Johns Hopkins, is leading a team of scientists that is developing new conducting materials for MEMS.

 

Specifically, the scientists write in their paper, future applications for MEMS devices, such as the Internet of Things, “demand the development of advanced materials with greater strength, density, electrical and thermal conductivity, dimensional stability, and microscale manufacturability. MEMS materials with this suite of properties are not currently available.” ACerS members Jessica Krogstad and Gianna Valentino are authors on the paper.

 

The team experimented with nickel alloys, adding molybdenum and tungsten because of their high melting points and heat-resistant properties. Vaporizing these metal alloys and atomically depositing them onto a substrate resulted in a thin film—29 micrometers thick—that “exhibited extraordinary properties,” according to a Johns Hopkins news release. The film was able to hold its shape when pulled and deformed, “three times greater than high-strength steel.”

 

“We thought the alloying would help us with strength as well as thermal stability,” Hemker adds in the release. “But we didn’t know it was going to help us as much as it did.”

 

According to the release, “the remarkable strength of the material is due to atomic-scale patterning of the alloy’s internal crystal structure. The structure strengthens the material and has the added advantage of not impeding the material’s ability to conduct electricity.”

 

Now that they have a viable material to work with, Hemker’s team plans to start creating MEMS components with it—and they’ve already filed a patent for their research.

 

The paper, published in Science Advances, is “Nanotwinned metal MEMS films with unprecedented strength and stability” (DOI: 10.1126/sciadv.1700685).

 


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