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New Thermoelectric Polymer Used For Ultra-Sensitive Heat Sensor

New Thermoelectric Polymer Used For Ultra-Sensitive Heat Sensor

The discovery of a new polymer with unique thermoelectric capability is key to the design of an ultra-sensitive heat sensor for biomedical and wearable technology.

A cross-institutional group of scientists has combined several engineering disciplines to develop a new flexible and printable sensor with unprecedented sensitivity to detect heat.

A team at the Laboratory of Organic Electronics at Linköping University in Sweden has developed the sensor thanks to a unique thermoelectric polymer, which provides the significant boost in sensitivity, researchers said.

Linköping University research fellow Dan Zhao with the ultra-sensitive printed sensor developed using a unique thermoelectric polymer she discovered. (Image source: Peter Holgersson, Linköping University)

Ionic Charge Carriers

The material uses ions as charge carriers instead of electrons, which is how typical thermoelectric materials function. This boosts the effect about 100 times, said the researchers—which included scientists from Linköping, Chalmers University of Technology, Stuttgart Media University, and the University of Kentucky.

Using the material, the team used a screen-printing technique to develop what they said is the first printed thermoelectric module in the world to operate in this way, giving the sensor its unique sensitivity, said Dan Zhao, a research fellow at Linköping University who discovered the new material.

Signal is 100 Times Stronger

For example, a thermoelectric material that uses electrons can develop 100 microvolts per Kelvin (µV/K) compared with 10 mV/K from the new material. The signal is thus 100 times stronger, and even a small temperature difference gives a strong signal, researchers said in a University news release.

Moreover, the material is easy to work with and versatile, paving the way for a number of new applications, she said. “The material is transparent, soft, and flexible and can be used in a highly sensitive product that can be printed and in this way used on large surfaces,” Zhao said.

The material itself is an electrolyte gel comprised of several ionic polymers. Some of the components are polymers with positively charged ions, which carry an electric current and are commonly found in the known material world.

Key to Functionality

However, what’s unique about the material is that one of the highly conductive polymer gels is of n-type, which means negatively charged ions carry the current, she said. This characteristic has been rare in materials until now, Zhao said.

This capability is what allowed for the design of a feature that is key to the sensor’s functionalityit is comprised by linked n- and p-legs, where the number of leg connections determines how strong a signal is produced, she said.

This design gives the heat sensor the ability to convert a tiny temperature difference to a strong signal. For example, a module with 36 connected legs gives 0.333 V for a temperature difference of 1 K, Zhao said. Researchers published a paper on their work in the journal Nature Communications.

Applications for the sensor are numerous, including novel smart bandages that can help heal wounds more quickly and even electronic skin for various wearable technology or robotic devices, Zhao said. Another possible application is to use the sensor to monitor the temperature in smart buildings, she said.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

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