A new ink that can be printed on textiles in a single step to form highly conductive and stretchable connections has been developed by researchers at the University of Tokyo.
The functional ink will enable electronic apparel such as sportswear and underwear incorporating sensing devices for measuring biological indicators such as heart rate and muscle contraction.
The ink is made out of a solution of silver flakes, organic solvent, fluorine rubber and fluorine surfactant. It can be stretched more than three times while maintaining conductivity.
A wrist-band muscle activity sensor was created using the ink, by printing an elastic conductor on a sportswear material and combining it with an organic transistor amplifier circuit.
The sensor can measure the muscle activity by detecting the muscle electrical potentials over an area of 4x4 square centimeters with nine electrodes placed 2 centimeters apart in a 3x3 gird.
Professor Takao Someya, University of Tokyo's Graduate School of Engineering, said, "Our team aims to develop comfortable wearable devices. This ink was developed as part of this endeavor. 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."