In a new study, North Carolina State University (NC State) researchers demonstrated they could print layers of electrically conductive ink on polyester fabric to make an e-textile that could be used in the design of future wearable devices.
Sources at the university report that since the printing method can be completed at room temperature and in normal atmospheric conditions, the researchers believe inkjet printing could offer a simpler and more effective method of manufacturing e-textiles. Additionally, the findings suggest they could extend techniques common in the flexible electronic industry to textile manufacturing.
Using a FUJIFILM Dimatix inkjet printer the researchers created a durable and flexible e-textile material. Part of their challenge was to find 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.
“Printing e-textiles has been a very big challenge for the e-textile industry,” said the study’s first author Inhwan Kim, a former graduate student at NC State. “We wanted to build a structure layer by layer, which has not been done on a textile layer with inkjet printing.”
They created the e-textile by printing layers of electrically conductive silver ink like a sandwich around layers of two liquid materials, which acted as insulators, then putting it on top of a woven polyester fabric. After they printed the layers of silver ink and insulating materials, made of urethane-acrylate, and poly(4-vinylphenol), they monitored the surface of the material using a microscope and found that the chemical properties of the insulating materials, as well as of the textile yarns, were important 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. “Also, if they are too bulky, people will not want to wear them.
“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.”