I recently came across a patent that described something that had fascinated me in my childhood. The patent described, to quote it, "devices for responding to thermal patterns and converting them to visible patterns." It took me a minute to realize that was a very clunky way to describe Mood Rings.
Yes, I'm talking about that 1970s relic that changed colors, supposedly in response to the wearer's mood. The ring had a large glass stone that turned a golden yellow if you were tense, blue if you were happy, and purple for moodiness.
It worked because the bottom of the stone was covered with something called a liquid crystal. The metal band of a Mood Ring conducted heat from the finger to that temperature sensitive liquid crystal, which changed color in response to temperature of the skin. What surprised me was that the technology used to create Mood Rings was intended for something much grander.
The idea of using temperature-sensitive liquid crystals to build devices occurred to James Fergason in the late 1950s. As a young engineer at Westinghouse, he came across the substance while working on another project. It intrigued him, and, in his words, he "burrowed in," he said, and "learned as much as possible about liquid crystals" in order to use them "to solve problems."
For the next thirty plus years, all that Fergason saw was uses for these liquid crystals. He designed a liner for a baby's bottle that indicated its temperature, and he proposed a bathtub mat that revealed, at a glance, the temperature of a shower. His first marketed invention, though, was a forehead band to measure the temperature of a person.
His greatest hope was to use the technology to save lives by diagnosing disease. He'd learned that a thin layer of these liquid crystals painted on the body would display a dramatic swirl of colors reflecting the temperatures under the skin. The patterns could reveal circulatory effects of diseases like hemophilia, arthritis, and diabetes. And the colors could reveal certain tumors. He even developed a way to screen for breast cancer. His methods caught on in France and Spain, but never in the U.S. Eventually,
Fergason's liquid crystal work didn't have the medical results he wanted, he has had a huge impact on our world beyond the 47 million mood rings sold. Today he says "I like to just sit on a plane and count how many LCD [Liquid Crystal Display] products there are in the in-flight magazines." This takes him a while. His liquid crystals are now in alarm clocks, radios calculators, laptop computer screens, and even make up the airliner's movie screen.
Copyright 2005 William S. Hammack Enterprises
