When we wonder if we’re running a fever, most of us take our temperature with a traditional or digital thermometer. More precise measurement can be hugely significant in detecting or predicting health issues in clinical settings. Studies at the Washington University School of Medicine have shown abnormal body temperature curves can be used to predict the diagnosis of sepsis, the leading cause of death in critically ill patients.
Scientists at the California Institute of Technology (Caltech) Division of Engineering and Applied Science and ETH Zurich were trying to make synthetic wood when they discovered something else. They found that pectin — a molecule found in plant cell walls — responds to small temperature changes in predicable and reliable ways. The researchers shifted their focus to creating a thin temperature-sensitive film made of pectin and water, as thin as 20 micrometers thick (like a strand of human hair). The pectin molecules have a double-strand structure that releases positively charged calcium ions when the temperature increases. This changes the electrical resistance of the film, which can be measured. The new material is more sensitive to temperature change by one or two orders of magnitude (depending on the temperature range) of current electronic skins. (It turns out that the material is similar to the mechanism that pit vipers use to sense prey.)
In its current state of development, the Caltech/ETH “electronic skin” has biomedical and robotic applications. Useful in temperatures ranging from 41 to 158 degrees Fahrenheit, the “skin” could be used with bandages to detect incipient infection, or grafted to prosthetics so amputees would have a way to sense temperature. Looking forward to creating pectin-based sensors for industrial applications where temperatures could run much higher, the researchers are studying substitutes for water which evaporates or can cause the material to bubble.