Super-strong silicon alternative promises sensors for ‘next tech frontier’
The new “super-strong” alloy both conducts electricity and can withstand high temperatures. The researchers see it as an alternative to silicon – the material used in most MEMS sensors today.
“For a number of years we’ve been trying to make MEMS out of more complex materials that are more resistant to damage and better at conducting heat and electricity,” says Kevin J. Hemker, chair of the Department of Mechanical Engineering at JHU’s Whiting School of Engineering.
Most current silicon-based MEMS devices will not work properly at higher temperatures and even lose their ability to conduct. In addition, silicon itself is brittle and prone to breaking. Better materials, say the researchers, will be needed for future MEMS devices – such as those used in Internet of Things (IoT) applications – which will need to withstand high heat and physical stress.
“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, say the authors of the paper. “MEMS materials with this suite of properties are not currently available.”
The researchers experimented with a number of materials to create their new alloy, especially combinations of metal containing nickel, which is often used in advanced structural materials, such as nickel-base superalloys that are used in jet engines. In addition, the metals molybdenum and tungsten were also added in hopes of reducing the tendency of pure nickel to expand in heat.
Alloy films were then created, that when separated from their substrate, exhibited “extraordinary properties.” According to the researchers, the freestanding alloy films, which had an average thickness of 29 microns, showed a tensile strength three times greater than high-strength steel.
“We thought the alloying would help us with strength as well as thermal stability,” says Hemker. “But we didn’t know it was going to help us as much as it did.”
The films have been shown to be able to withstand high temperatures and are both thermally and mechanically stable, say the researchers. The team has filed a provisional patent application for the alloy and next plans to begin shaping the films into MEMS components.