Printable, elastic conductors offer wearable possibilities

A new elastic, printable and highly conductive ink developed at the University of Tokyo holds the potential to facilitate electronic apparel, such as sportswear and underwear, incorporating sensing devices to measure such biological indicators as heart rate and muscle contraction.

Current printed electronics—transistors, light-emitting diodes and solar panels—can be printed on plastic or paper, 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.

Professor Takao Someya’s research group at the university’s Graduate School of Engineering has developed an elastic conducting ink that is easily printed on textiles and patterned in a single step, much like printing ink on paper. The new ink comprises silver flakes, organic solvent, fluorine rubber and fluorine surfactant, and exhibits high conductivity even when stretched to more than three times its original length.

The researchers created a wrist-band muscle-activity sensor by printing an elastic conductor onto a sportswear material and combining it with an organic transistor amplifier circuit. This sensor can measure muscle activity by detecting muscle electrical potentials.