Fraunhofer IPMS develops system to optically check fabric for recycling...

17 Oct 2023

...and Danish project “HyperSort” deploys super continuum source and chemometrics to sort textiles, cut food waste.

Tech uses smart phone, AI and IR spectroscopy; optimize analysis of mixed fabrics, old clothes.

Researchers at Fraunhofer IPMS have developed an ultra-compact near-infrared spectrometer suitable for recognizing and analyzing textiles. Mixed fabrics can also be reliably identified through the combination of imaging, artificial intelligence algorithms and spectroscopy.

Its developers say technology could be used to optimize recycling old clothing, sorting textiles according to type. A miniaturized version of the system can even be fitted into a smart phone. This could lead to a host of new applications — from checking clothes when out shopping to detecting counterfeits.

The analyzer can also reliably recognize mixed fabrics. Possible applications range from checking fabrics when out shopping to cleaning garments correctly, and even sustainable, sorted recycling. The spectrometer is so tiny, it can be integrated into a smart phone.

Researchers at Fraunhofer rely on near-infrared spectroscopy to achieve the required reliability and accuracy when identifying textiles. The system works for wavelengths between 950 and 1900 nm, which is close to the visible spectrum.

Advantages of near-infrared technology include being easy to use and having a wide range of applications. “We combine NIR spectroscopy with imaging and AI to achieve higher accuracy when recognizing and analyzing objects,” said Dr. Heinrich Grüger, research scientist in the Sensoric Micromodules department at IPMS.

Firstly, a conventional camera module captures an image of the garment. The AI selects a specific point from the fabric’s image data to be examined by the spectral analyzer module. Light reflected from the fabric is captured by the spectrometer module. There, it passes through an entrance slit, is transformed into parallel light beams using a collimating mirror and projected onto a grating using a scanning mirror.

Depending on the angle of incidence and exit, the grating splits the light beams into different wavelengths. Light reflected from the grating is directed by the scanner mirror to a detector which captures the light as an electrical signal. An A/D converter then digitizes these signals, which are subsequently analyzed in the signal processor. The resulting spectrometric profile for the textile fabric reveals which fibers it is made from by comparing to a reference database.

“The optical resolution is 10 nanometers. This high resolution means the NIR spectrometer can also use AI to identify mixed fabrics such as items of clothing made from polyester and cotton,” said Grüger. Measuring just 10 mm × 10 mm and being 6.5 mm thick, the system is so compact it could easily be integrated into a standard smart phone.

Recycling clothing

Grüger sees an important application for the AI-controlled spectrometer when it comes to recycling. According to the Federal Statistical Office of Germany, approximately 176,200 tons of textile and clothing waste was collected from private homes in Germany in 2021.

NIR spectroscopy could improve recycling efficiency and reduce the mountain of old clothing. This would enable companies that recycle old clothing to sort it more efficiently and faster. Textiles that are still in one piece, for instance, go to the second-hand trade.

Damaged textiles are sorted for recycling, and the fibers they are made from, such as linen, silk, cotton or lyocell, can be reused. Severely soiled textiles would be incinerated or processed into insulation mats, for example. Spectroscopic identifies and sorts textiles more accurately and much faster than a human can.

If NIR spectroscopy was to be integrated into a smartphone, end-users might also benefit from the Fraunhofer institute’s technology. When buying clothes, a quick check with a smartphone reveals whether that expensive silk scarf is genuinely made from silk, or whether that exclusive dress from the fashion label is not instead a counterfeit, exposed through an alternative mix of fabrics.

There are also applications beyond the textile industry. Smart phones fitted with spectrometers might be used to provide information about the quality of groceries such as fruit and vegetables when out shopping. It might also be used to examine skin: a scan with the cell phone spectrometer could identify particularly dry or greasy patches.

“HyperSort” project uses lasers and chemometrics to sort textiles, cut food waste

HyperSort, a new project supported by a 14 million DKK investment ($1 million) from the Innovation Fund, unites laser technology, chemometrics, textile recycling, and meat processing experts to create an advanced hyperspectral imaging system. Its primary objectives are to improve textile sorting efficiency and reduce food waste.

The project addresses challenges in hyperspectral imaging, using a supercontinuum light source from NKT Photonics to enhance resolution, penetration depth, and material differentiation. This technology has applications in, for example, food analysis due to its minimal heating effects and operational distance capabilities. The aim is to develop an industry-ready hyperspectral optical engine to advance textile recycling and side-stream meat processing, ultimately making a significant global impact.

The project builds on NKT Photonics’ experience in the development of supercontinuum lasers, expertise at the University of Copenhagen and the University of the Basque Country, and researchers in contact with the industry within meat processing and textile recycling. The consortium also includes a fast-growing SME, NLIR, which develops detectors for infrared wavelengths based on a patented upconversion technique.

HyperSort has two goals: to improve textile recycling, especially by differentiating complex textiles; and to optimize meat processing, by enabling the prediction of the quality of the finished products – so that waste production is avoided.