[Image above] Strip of a new biodegradable smart textile made of inkjet-printed graphene. Credit: Marzia Dulal, University of Southampton

 

Since the mid-1900s, cities around the world have held so-called Fashion Weeks to provide fashion designers, brands, and “houses” a space to publicly display their latest collections.  In recent years, electronic “e” textiles, also dubbed smart textiles, have graced the runway during various Fashion Weeks, including in Berlin, Milan, and London.

At a New York City show in 2019, Stratasys, a leader in 3D printing, helped produce a polyester dress that incorporated thousands of spherical microcells made of photopolymers. At the slightest movement of the wearer, the dress changed colors. Credit: Stratasys

While smart textiles will surely make an appearance at the several Fashion Weeks scheduled this month—including in New York City, London, and Milan—fashion is but one small part of the smart textiles market. These products find wide application in healthcare and fitness, as discussed in this review, as well as nonwearable uses, such as interior design.

Engineered materials play a critical role in smart textile development, as demonstrated during The Wearables in Smart Fabrics Fashion Show at the Materials Research Society 2018 Spring Meeting. Numerous manufacturing processes, described here, are used to incorporate various (nano)materials into the fabric, including polymers, metals, oxides, and MXenes.

As demand for smart textiles increases, a major challenge will be what to do with all the additional electronic waste, including sensors, batteries, and lights found in smart textiles. Already, about 50 million to 60 million tons of e-waste is generated per year, leading to the contamination of the environment.

Another source of waste from smart textiles is the fabric itself. The average U.S. consumer throws away 81.5 lbs. of clothes every year, totaling an estimated 11.3 million tons of textile waste. Though many types of fabric can be recycled, the complicated sorting process often makes the process uneconomical. Fabric that cannot be easily recycled includes blended fabrics, recycled polyester, wet and unclean clothing, and anything with fixtures, according to Fashion for Good.

In December 2024, researchers led by the University of Southampton and the University of the West of England (UWE Bristol) developed a solution that addresses both types of waste. As described in an open-access paper, their SWEET technology, which stands for ”Smart, Wearable, and Eco-friendly Electronic Textiles,” consists of the following components:

  1. Sensing layer consisting of either inkjet-printed graphene or a biodegradable conductive polymer called PEDOT: PSS. The ink-jet printing process is environmentally friendly because it deposits the exact amount of functional materials required with almost no material waste, as well as uses less water and energy compared to conventional screen printing. Furthermore, the graphene ink was prepared using a solution of graphite powder and deionized water because water-based inks are typically nontoxic and less detrimental to human health.
  2. Interface layer consisting of an insulator paste, which was applied to the base fabric before inkjet printing of the sensing layer. This layer allowed successful printing of continuous conductive tracks.
  3. Base fabric consisting of a textile called Tencel, which is made from biodegradable wood with appropriate softness, breathability, and flexibility. This textile is considered renewable because it is fabricated using a closed-loop production method with a higher resource efficiency (99% recovery rate for water and solvent) and little negative environmental impact.

Optimized layers (50 of PEDOT:PSS and 120 of graphene) were inkjet printed onto the surface-treated Tencel fabric. At the edges of the printed textile, electrode connecting wires were attached to collect current. Curing time and temperature were optimized at 100°C (212°F) for 5 minutes to achieve optimal conductivity.

To test the sensing capabilities of this smart textile, SWEET was integrated with gloves using double-sided adhesive tape, ensuring a secure and stable connection between the sensor and glove materials. Five human subjects wore these gloves to measure their electrocardiogram signals and skin temperature. Results confirmed the material can effectively and reliably measure both heart rate and temperature at the industry standard level.

To measure the smart textile’s biodegradable properties, the SWEET sensors were buried in an incubator in 150 mm of soil with a 6.5 to 6.8 pH, a temperature of 29°C (84°F), and a relative humidity of around 90%. After four months, the fabric had a 48% decrease in weight and 98% decrease in strength, which indicated a relatively rapid and effective decomposition.

Furthermore, a laboratory-scale life cycle assessment, based on ISO 14040 and 14044 standards, revealed the graphene-based electrodes had up to 40 times less impact on the environment than standard electrodes and were three times less impactful than the PEDOT:PSS ones. In global warming potential terms, graphene’s impact was about 71% lower than PEDOT:PSS and about 98% lower than the standard electrode.

In a University of Southampton press release, coauthor Shaila Afroj, associate professor of sustainable materials at the University of Exeter, says achieving this environmental performance is a “significant milestone.”

“It demonstrates that sustainability doesn’t have to come at the cost of functionality, especially in critical applications like healthcare,” she says.

The open-access paper, published in Energy & Environmental Materials, is “Sustainable, wearable, and eco-friendly electronic textiles” (DOI: 10.1002/eem2.12854).

Author

Laurel Sheppard

CTT Categories

  • Environment
  • Material Innovations