North Carolina State University researchers have published a study demonstrating they could print layers of electrically conductive ink on polyester fabric that could be used in wearable devices.
The printing method can be achieved at room temperature and in normal atmospheric conditions, offering a simpler and more effective method of manufacturing e-textiles. They reported their findings in the journal ACS Applied Materials & Interfaces.
“Inkjet printing is a rapidly advancing new technology that’s used in flexible electronics to make films used in cellphone displays and other devices,” said the study’s corresponding author Jesse S. Jur, professor of textile engineering, chemistry, and science at NC State. “We think this printing method, which uses materials and processes that are common in both the electronics and textiles industries, also shows promise for making e-textiles for wearable devices.”
Finding the right composition of materials so the liquid ink would not seep through the porous surface of the textile materials and lose its ability to conduct electricity proved to be a challenge.
The study’s first author Inhwan Kim, said “We wanted to build a structure layer by layer, which has not been done on a textile layer with inkjet printing. It was a big struggle for us to find the right material composition.”
Credit: Inhwan Kim
First, the researchers printed layers of electrically conductive silver ink like a sandwich around layers of two liquid materials, which acted as insulators. Then, those sandwich layers were printed on top of a woven polyester fabric and monitored the surface of the material using a microscope. They found that the chemical properties of the insulating materials and the textile yarns, were crucial to maintaining the ability of the liquid silver ink to conduct electricity, and prevent it from penetrating through the porous fabric.
“We wanted a robust insulation layer in the middle, but we wanted to keep it as thin as possible to have the entire structure thin, and have the electric performance as high as possible,” Kim said.
The researchers tested the electrical performance of the e-textile after more than 100 cycles of bending, finding the e-textile didn’t lose its electrical performance. In future work, they want to improve the materials’ electrical performance as well as increase the material’s breathability.
In the future, they want to create an e-textile that could be used in wearable electronics such as biomedical devices, or used as a battery to store power for electronic devices.
“We were able to coat the ink on the fabric in a multi-layer material that’s both durable and flexible,” Kim said. “The beauty of this is, we did everything with an inkjet printer — we didn’t use any lamination or other methodologies.”