New 3D printing method for more sensitive strain gauges

Scientists, including one of Indian origin, have developed a 3D printing technique for manufacturing strain gauges with improved sensitivity, and capability for use in high-temperature applications.
Strain gauges are simple devices used to measure strain, or pull, on an object. They are used in weighing stations, airplane wings, and bridges.
Stretching a strain gauge changes its resistance which tells us how much deformation the object is undergoing.
"Anywhere there is deflection of a mechanical system, you will see strain gauges; which is a lot of places!" said Rahul Panat, an associate professor at Carnegie Mellon University in the US.
Panat has developed a new 3D printing technique for manufacturing strain gauges, along with collaborators from Washington State University and the University of Texas at El Paso.

The new method significantly improves the sensitivity of strain gauges and increases their capabilities for use in high-temperature applications, researchers said.

They fabricated this strain gauge using aerosol jet printing, a 3D printing method that creates a porous film by controlled sintering of nanoparticles that partially coalesce them using heat.
When stretched, this porous film - which contains many tiny holes that result from the 3D printing method, also known as additive manufacturing - is able to contract more than a solid film, the typical form of strain gauges fabricated using traditional manufacturing methods.
This new manufacturing method breaks what is known as the Poisson Ratio, the limit to how sensitive a solid strain gauge can be, the researchers said.

The Poisson Ratio of a material describes how much a material will contract in one direction when it is stretched in another direction.
The maximum Poisson Ratio a solid material can have is about 0.5, according to Panat.
"Because of the porosity of the film, we are seeing an effective Poisson Ratio of approximately 0.7 - which means we have about a 40 per cent increase in the lateral contraction for a given deformation of the film," said Panat.
"That makes the strain gauge much more sensitive to measurement," he said.