Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a flexible, expandable, self-powered thermometer that can be integrated into smart robots and expandable electronics.
The research was published in the Proceedings of the National Academy of Sciences.
Zhigang Suo is the Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials at SEAS and senior author of the paper.
“We have developed soft temperature sensors with high sensitivity and fast response time, opening up new possibilities for creating novel human-machine interfaces and soft robots in healthcare, engineering and entertainment,” Suo said.
Structure of the thermometer
The thermometer has three parts: an electrolyte, an electrode, and a dielectric material that separates them. The electrolyte/dielectric interface accumulates ions, and the dielectric/electrode interface accumulates electrodes.
With the charge imbalance between the two, this results in an ion cloud in the electrolyte. This ionic cloud then changes in thickness and generates a voltage when the temperature changes. While tension is temperature sensitive, it is insensitive to stretch.
Customization of the sensor
Yecheng Wang is a postdoctoral fellow at SEAS and first author of the paper.
“Because the design is so simple, there are many different ways to customize the sensor, depending on the application,” Wang said. “You can choose different materials, arranged in different ways and optimized for different tasks.”
The researchers were able to arrange the electrolyte, dielectric, and electrode in different configurations, resulting in four designs for the temperature sensor. They tested it by first embedding the sensor in a flexible clamp before measuring the temperature of a hot hard-boiled egg. The sensors were more sensitive than traditional thermoelectric thermometers and they were able to react to temperature changes within 10 milliseconds.
“We demonstrated that these sensors can be made small, stable, and even transparent,” Wang said.
The thermometer can measure temperatures up to 200 degrees Celsius or down to -100 degrees Celsius depending on the materials used.
“This highly customizable platform could usher in new developments to enable and improve the Internet of everything and everyone,” Suo said.