The researchers integrated their stretchable sensor into a soft gripper and measured the temperature of a hot hard-boiled egg. Photo: Harvard SEAS.The next generation of soft robotics, smart clothing and biocompatible medical devices are going to need integrated soft sensors that can stretch and twist with the device or wearer, but most of the components in traditional sensing devices are rigid. Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a soft, stretchable, self-powered thermometer that can be integrated into stretchable electronics and soft robots.
“We have developed soft temperature sensors with high sensitivity and quick response time, opening new possibilities to create new human–machine interfaces and soft robots in healthcare, engineering and entertainment,” said Zhigang Suo, professor of mechanics and materials at Harvard SEAS and senior author of a paper on this work in the Proceedings of the National Academy of Sciences.
The thermometer consists of three simple parts: an electrolyte, an electrode and a dielectric material to separate the two. The electrolyte/dielectric interface accumulates ions while the dielectric/electrode interface accumulates electrons. The charge imbalance between these two interfaces sets up an ionic cloud in the electrolyte.
When the temperature changes, the ionic cloud changes thickness, and a voltage is generated. This voltage is sensitive to temperature, but insensitive to stretch.
“Because the design is so simple, there are so many different ways to customize the sensor, depending on the application,” said Yecheng Wang, a postdoctoral fellow at Harvard SEAS and first author of the paper. “You can choose different materials, arranged in different ways and optimized for different tasks.”
By arranging the electrolyte, dielectric and electrode in different configurations, the researchers developed four designs for the temperature sensor. In one test, they integrated the sensor into a soft gripper and measured the temperature of a hot hard-boiled egg. The sensors are more sensitive than traditional thermoelectric thermometers and can respond to changes in temperature within about 10 milliseconds.
“We demonstrated that these sensors can be made small, stable and even transparent,” said Wang.
Depending on the materials used, the thermometer can measure temperatures upwards of 200°C or as cold as -100°C. “This highly customizable platform could usher in new developments to enable and improve the internet of everything and everyone,” said Suo.
This story is adapted from material from Harvard SEAS, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.