The original skin electrodes for
transcutaneous electrical nerve stimulation (TENS) in the 1860s
consisted of rollers and brushes.
The Electreat device manufactured during WWI used saline soaked pads
and sponges. When TENS became a high volume therapy in the 1970s
more efficient means of conducting electrical stimulation across the skin
were sought.
The first of the modern TENS skin electrodes were conductive
silicone pads taped to the skin over a conductive gel. These were
easily dislodged and the gel would tend to dry out.
A truly innovative TENS electrode was the Medtronic "Epiductive"
skin electrode. It consisted of a microparticle imprgnated
conductive tape activated by a solvent which allowed microparticles to
enter the epidermis and make a highly efficient electrical contact.
Further research into Epiductive and its use in pattern displays on skin
were not pursued by Medtronic.
Shown here is a 3M Corporation compound skin electrode
utilizing a contained gel on its skin surface. The hardy and effective
design serves well for TENS as well as external stimulation for bone
growth devices and different types of skin monitoring, particulaly for
cardiologic purposes.
Skin electrodes are more practical today but it is clear that the
technology remains in its infancy when compared to more sophisticated
applications of transcutaneous drug delivery, pattern stimulation and
other, more advanced applications.