Researchers have developed a new “conductive” ink that can be used to create wearable electronic apparels. University of Tokyo’s new functional ink will enable electronic apparel such as sportswear and underwear incorporating sensing devices for measuring a range of biological indicators such as heart rate and muscle contraction.
Current printed electronics, such as transistors, light emitted diodes and solar panels, can be printed on plastic or paper substrates, but these substrates tend to be rigid or hard. The use of soft, stretchable material would enable a new generation of wearable devices that fit themselves to the human body. However, it has proved difficult to make an ink that is both highly conductive and elastic without a complicated multi-step printing process. Researcher Takao Someya’s team has developed an elastic conducting ink that is easily printed on textiles and patterned in a single printing step. This ink is comprised of silver flakes, organic solvent, fluorine rubber and fluorine surfactant.
The ink exhibited high conductivity even when it was stretched to more than three times its original length, which marks the highest value reported for stretchable conductors that can be extended to more than two and a half times their original length. Using this new ink, the group created a wrist-band muscle activity sensor by printing an elastic conductor on a sportswear material and combining it with an organic transistor amplifier circuit. The study appears in Nature Communications.