Researchers have developed a new fiber that combines the flexibility of cotton with the conductivity of the polymer polyaniline. The innovative material, detailed in the journal Carbohydrate Polymers, shows potential for creating wearable e-textiles for applications such as health monitoring and hazardous exposure detection.

A single-strand fiber developed at Washington State University combines the flexibility of cotton with the conductivity of a polymer called polyaniline, showing great promise in wearable electronic textiles. The Washington State University researchers tested the fibers with one system that powered LED lights and another that sensed ammonia gas, detailing their findings in the journal Carbohydrate Polymers.

A microscopic image of the newly developed fiber, showing its side-by-side blend of cotton on one side and a polyaniline polymer that carries an electrical current on the other side. Source: Washington State University

"We split a fiber into two parts: One side is traditional cotton: flexible and strong enough for daily use, and the other side is a conductive material. The cotton can support the conductive material, and the conductive material can provide the required functions."

Potential applications of wearable technology

Although more development work is needed, the researchers' idea is to integrate such fibers into clothing as sensor patches with flexible circuits. The patches could become part of the uniforms of firefighters, soldiers or workers handling chemicals to detect exposure to dangerous substances. Other applications include health monitoring or sports shirts that can do more than current fitness monitors.

Liu said: "We now have some smart wearable devices, such as smart watches that can track your movements and human vital signs, but we hope that in the future your daily clothing can also implement these functions. Fashion is not just about color and style as many people think, fashion is the science itself."

Liu Hang, a textile researcher at Washington State University. Source: Washington State University DeanHare

Technical challenges and solutions

In this study, the Washington State University team worked to overcome the challenges of mixing conductive polymers with cotton cellulose. A polymer is a large molecule with a repeating pattern. In this case, the researchers used polyaniline (also known as PANI), a synthetic polymer with conductive properties that is already used in applications such as printed circuit board manufacturing.

Although polyaniline itself is conductive, it is brittle and cannot be made into textile fibers. To solve this problem, researchers at Western Sydney University dissolved cotton cellulose extracted from recycled T-shirts into one solution and conductive polymers into a separate solution. The two solutions are then combined side by side and the material is extruded to create a fiber.

Hang Liu, a textiles researcher at Washington State University, looks at microscopic images of the newly developed fibers, which show the fibers mixed side by side, with cotton on one side and a polyaniline polymer that carries an electric current on the other. Source: Washington State University DeanHare

The results showed that the interface was well bonded, meaning the molecules of the different materials stayed together during stretching and bending. Achieving the right mix at the interface between cotton cellulose and polyaniline was a delicate balance.

"We want the two solutions to work so that when the cotton and the conductive polymer come into contact with each other, they will mix together to some extent to form an adhesive, but we don't want them to mix too much or the conductive properties will be reduced," Liu said.

Reference: "Novel structural design of cellulose-based conductive composite fibers for wearable electronic textiles", author: Wangcheng Liu, Hang Liu, Zihui Zhao, Dan Liang, Wei-HongZhong and Jinwen Zhang, August 18, 2023, "Carbohydrate Polymers".

DOI:10.1016/j.carbpol.2023.121308

Compiled source: ScitechDaily