Magnetic particles to be temperature sensors

October 13, 2020 //By Nick Flaherty
The Thermal Magnetic Imaging and Control (Thermal MagIC) project at NIST in the US is developing nanoscale temperature sensors
A research project at NIST in the US is developing nanoscale temperature sensors that can be embedded in all kinds of materials

The Thermal Magnetic Imaging and Control (Thermal MagIC) at the National Institute of Standards and Technology (NIST) in Maryland aims to develop a nanoscale array of ultra-sensitive temperature sensors and the analog test equipment to read the array at a distance.

The system will be the first to make real-time measurements of temperature in medical implants, refrigerators, electronics and potentially the human body. It will use nanometer-sized objects whose magnetic signals change with temperature. These sensors would be incorporated into the liquids or solids being studied, for example in melted plastic that might be used as part of an artificial joint replacement, or the liquid coolant being recirculated through a refrigerator. A remote sensing system would then pick up these magnetic signals, meaning the system being studied would be free from wires or other bulky external objects.

The final product could make temperature measurements that are 10 times more precise than state-of-the-art techniques, accurate to within 25 millikelvin in 100ms. The measurements would be traceable to the International System of Units (SI) from 200 to 400 K (-73 to 126ºC). There is potential for a much larger temperature range, stretching from 4K to 600K, but that is not a part of current development plans.

"This is a big enough sea change that we expect that if we can develop it -- and we have confidence that we can -- other people will take it and really run with it and do things that we currently can't imagine," said Cindi Dennis, a physicist at NIST on the project.

The first step is creating the nanoscale magnets that will give off strong magnetic signals in response to temperature changes. These need to be 10 times more sensitive to temperature changes than any objects that currently exist and so will use multiple magnetic materials.

Next: Modelling the nanoparticle materials

Picture: 
A prototype 8nm nanoparticle made of iron oxide and cobalt that can be encased in a shell of a different material. Adam Biacchi/NIST

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