Engineers develop super strong material for IIoT sensors

The industrial internet of things offers the ability to take technology to new heights; however, the current microscopic sensor tech has some limitation. And with more and more devices becoming connected, researchers are looking for new options.

Image credit: JANAKAMAHARAGEDHARMASENA (Johns Hopkins University)

For the most part, the sensors are made from silicon. But Johns Hopkins University materials scientist and mechanical engineer Kevin Hemker is leading a team to develop a new sensor material.

The team hopes that this new material will help ensure microelectromechanical systems (MEMS) are compatible with the latest technological demands.

Hemker, who chairs the Department of Mechanical Engineering at JHU’s Whiting School of Engineering, explains that the team has been trying to make MEMS out of  more complex materials that will allow the sensors to be damage resistant and better conductors of heat and electricity.

MEMS devices tend to have extremely small widths and are shaped out of silicon. However, silicon can be very brittle and is not conducive to temperature change—even minimal temperature difference causes them to lose strength. As devices become more complex and applications more diverse, the team looks to new materials for MEMS devices.

“These applications demand the development of advanced materials with greater strength, density, electrical and thermal conductivity” that hold their shape and can be made and shaped at the microscopic scale, the authors of the paper wrote. “MEMS materials with this suite of properties are not currently available.”

The researchers considered combinations of metal containing nickel, which is commonly used in advanced structural materials. Considering the need for dimensional stability, the researchers experimented with adding molybdenum and tungsten to curb the degree to which pure nickel expands in heat.

The team developed the material at the laboratory at Johns Hopkins by hitting targets with ions to vaporize the alloys into atoms, depositing them onto a surface, or substrate. This created a film that can be peeled away, thus creating freestanding films with an average thickness of 29 microns.

When pulled, these freestanding alloy films showed a tensile strength three times greater than high-strength steel. While a few materials have similar strengths, they either do not hold up under high temperatures or cannot be easily shaped into MEMS components.

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

He said the remarkable strength of the material is due to atomic-scale patterning of the alloy’s internal crystal structure.

The structure “has given our films a terrific combination, balance of properties,” Hemker said.

The films can withstand high temperatures and are both thermally and mechanically stable, making them ideal for these applications.

The team’s next step is looking at how the film can be shaped into MEMS components. and they are busy planning the next step of development, which involves shaping the films into MEMS components.

The other researchers on the project were Timothy P. Weihs, professor of materials science and engineering; Jessica A. Krogstad, Gi-Dong Sim, and K. Madhav Reddy, who were post-doctoral fellows during various stages of the project; research scientist Kelvin Y. Xie; and current graduate student Gianna Valentino.

The results of their successful experiments are in the current issue of the journal Science Advances.

www.jhu.edu