A new sweat meter developed at University of Oslo and the National Hospital of Norway may provide diabetics a non-invasive way to detect low blood sugar levels. There’s a noticeable change in sweat patterns when blood glucose approaches dangerously low levels, hence there is hope that the new technology will be sensitive enough to become a preemptive tool to avoid clinically significant hypoglycemia.
The researchers are now preparing for clinical testing of the new devices on diabetic patients, and other groups are finding use for the sweat sensors for studying kids with chronic fatigue syndrome and night sweats.
From the announcement:
The sweat meter sends a small electrical current through the outer part of the skin, into the sweat glands and out onto the surface again. This layer of skin, which consists of dead horn cells, is as thin as the plastic film you use to wrap food, only 10 to 15 micrometers thick. Horn cells are poor conductors of electricity. On the other hand, sweat is a good conductor of electricity. Sweat is made up of saltwater. As is known, saltwater conducts electricity. The conductivity of the skin increases, therefore, when the sweat pores are filled with sweat.
Although the sweat meter looks simple, it is packed with advanced technology.
A current passes through the electrodes. The sweat meter requires at least three electrodes.
“With two electrodes, it’s not possible to separate the signals from the various electrodes from each other. By using multiple measuring points, we get a control system where we can keep track of the contributions of each electrode,” says Tronstad.
They have developed special electrodes that do not affect the measurements.
“This ensures optimal focus on the outer part of the skin where sweating occurs.”
The electrodes in the old models, which University of Oslo researchers developed a few years ago, created artificial signals. The measurements were not that reliable.
While the old, familiar lie detectors use direct current, the new sweat meter uses alternating current. With DC the current direction is constant. With AC the direction of the current changes all the time.
“DC has a long history and is used in conservative research communities. Some scientists in psychological communities cling to this method. We were met with scepticism, but were eventually accepted.”
The natural electrical power of the body, such as muscle and nerve cells, is equal to 0.15 V, one-hundredth of an ordinary 1.5 V battery.
“This current is direct current. The problem is that it’s not possible to measure direct current with direct current, since it isn’t possible to separate these two direct currents from each other. Moreover, AC doesn’t affect biological material as much as DC.”
Link at University of Oslo: Sweat meter warns patients of dangerously low blood sugar …