Previous attempts to create a highly conductive and elastic ink without using a complicated multi step printing process have not been successful. However, the University of Tokyo group has developed an elastic conducting ink comprised of silver flakes, organic solvent, fluorine rubber and a fluorine surfactant. The ink exhibited high conductivity, even when stretched to more than three times its original length. This is said to represent the highest value reported for stretchable conductors.
Professor Takao Someya said: "The biggest challenge was obtaining high conductivity and stretchability with a simple one-step printing process. We were able to achieve this by use of a surfactant that allowed the silver flakes to self-assemble at the surface of the printed pattern, ensuring high conductivity."
Using the ink, the group created a wristband muscle activity sensor by printing an elastic conductor on a sportswear material and combining it with an organic transistor amplifier circuit. This sensor can measure muscle activity by detecting muscle electrical potentials over an area of 4 x 4cm, with nine electrodes placed 2cm apart in a 3x3 grid.
