Research engineers have tapped into a new ink that can be printed onto textiles in one step, forming connections that are both highly conductive and stretchable. The technology could pave the way for electronic apparel, allowing clothing to measure a number of biological indicators like heart rate and muscle contraction by way of sensors.
So what’s unique about this ink? Printed electronics are already on the market and are used in plastic and paper substrates. However, they’re typically rigid. In contrast, the ink created by a team at the University of Tokyo is highly conductive while also elastic.
The ink is made from organic solvent, silver flakes, fluorine surfactant and fluoroelastomer. According to the engineers, it remains highly conductive even when it’s stretched to more than three times its size – a supposed record for stretchable conductors.
"The biggest challenge was obtaining high conductivity and stretchability with a simple one-step printing process,” says professor Takao Someya. “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."
The team tested its ink and developed a wrist band featuring a muscle activity sensor. They started out by printing an elastic conductor onto a sportswear material and integrated it with an organic transistor amplifier circuit. The sensor measures muscle electrical potentials “over an area of 4x4 square centimeters with nine electrodes placed 2 centimeters apart in a 3x3 grid.”
The group recently published a paper in the journal Nature Communications titled, "Printable elastic conductors with a high conductivity for electronic textile applications.” For more information, visit the journal’s website.