Electronic fibres printed directly onto fabrics

Seeking a solution for comfortable wearable electronics, Chinese researchers have developed a way to simply print flexible fibres onto transitional textiles or clothes. Writing in the journal Matter, the researchers described how they printed patterns that can harvest and store electricity onto fabrics.

“We used a 3D printer equipped with a home-made coaxial nozzle to directly print fibres on textiles and demonstrated that it could be used for energy-management purposes,” said senior author Yingying Zhang, a professor at Tsinghua University. “We proposed a coaxial nozzle approach because single-axial nozzles allow only one ink to be printed at a time, thus greatly restricting the compositional diversity and the function designing of printed architectures.”

Zhang and her colleagues made their first 3D-printed e-textiles using two inks — a carbon nanotube solution to build the conductive core of the fibres and silkworm silk for the insulating sheath (although other labs could choose materials that adjust for flexibility, biocompatibility and waterproofness). Injection syringes filled with the inks were connected to the coaxial nozzle, which was fixed on the 3D printer. These were used to draw customer-designed patterns, such as Chinese characters meaning PRINTING, the English word SILK and a picture of a pigeon.

This approach differs from other groups who are manually sewing electrical components, such as LED fibres, into fabrics, but these multistep processes are labour-intensive and time-consuming. The strength of using a 3D printer is that it can build versatile features into fabrics in a single step.

The approach is also cheap and easy to scale, as the nozzle is compatible with existing 3D printers and the parts can be swapped. However, a drawback is that the resolution of what can be printed is limited to the mechanical movement accuracy of the 3D printer and size of the nozzles.

“We hope this work will inspire others to build other types of 3D printer nozzles that can generate designs with rich compositional and structural diversity and even to integrate multiple co-axial nozzles that can produce multifunctional e-textiles in one-step,” Zhang said.

“Our long-term goal is to design flexible, wearable hybrid materials and electronics with unprecedented properties and, at the same time, develop new techniques for the practical production of smart wearable systems with integrated functions, such as sensing, actuating, communicating and so on.”

Image caption: This schematic illustration shows smart clothes for energy management and its performance. Inset (i) shows the output Isc density of a smart gridline pattern printed on the underarm sleeve of a shirt generated by an arm moving. Inset (ii) is the rectifying circuit diagram of the power system. Inset (iii) shows the rectified output Isc density of the smart pattern. Image credit: Yingying Zhang.

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