Laser-drilled microplastic filter tested in wastewater treatment plants

Until now, sewage treatment plants have not been able to sufficiently filter out tiny microplastics in wastewater, but this may soon change: the first laser-drilled microplastic filter is being tested at a sewage treatment plant. It contains sheets with extremely small holes of only 10 micrometers in diameter. The technology to efficiently drill millions of such holes was developed at the Fraunhofer Institute for ILT Laser Technology, and now engineers at the institute are developing ultrashort pulse (USP) laser technology in the kW range. Visitors can learn more about the microplastic filter and ultrashort pulse lasers at Fraunhofer booth A6.441 at LASER World of PHOTONICS.

Today, sustainability is not an option, but more of an obligation, regardless of the technology being developed. As a result, the laser industry is increasingly using USP technology to improve durability in many projects. Lasers are already being used to increase the efficiency of hydrogen technology and to generate absolutely leak-proof battery boxes in electromobility applications.

As part of the BMBF-funded “SimConDrill” project, Fraunhofer ILT has teamed up with industrial partners to build a filter that, for the first time, can remove microplastics from wastewater. “Basically, our challenge was to drill as many holes as possible, as small as possible, in a sheet of steel in the shortest possible time,” explains Andrea Lanfermann, project manager at Fraunhofer ILT.

Mobile filtration plant in a sewage treatment plant

This has been achieved. After the development of the process at Fraunhofer ILT, experts from LaserJob GmbH drilled 59 million holes with a diameter of 10 micrometers in a filter sheet, thus creating a filter prototype. Fraunhofer researchers are also collaborating with three other companies on this ambitious project. In addition to the project coordinator KLASS Filter GmbH, LUNOVU GmbH and OptiY GmbH are also involved.

In the meantime, the laser-drilled metal foils have been installed in the patented cyclone filter from KLASS Filter GmbH and subjected to extensive testing. In the first test, the fine powder from the 3D printers was filtered out of the contaminated water. The installation is currently being tested in real conditions in a wastewater treatment plant.

Process knowledge is key

Drilling millions of holes one after another takes time, but can be done faster with the multi-beam process, in which an array of identical beams is generated from a laser beam through a special optical system. Fraunhofer ILT used this process with an ultrashort pulse laser (TruMicro 5280 Femto Edition) to punch holes simultaneously with 144 beams. The basis for these applications is detailed process knowledge, which has been collected at the Fraunhofer ILT over decades and implemented in the corresponding models and software. Thanks to this expertise, the parameters can be varied on the computer and the optimal process parameters found quickly. The robustness of the process can also be analyzed before the application is tested.

Alongside this drilling application, a consortium of six partners is working on the best way to integrate a multibeam processing system into an industrial machine. In the European “Multiflex” project, researchers and industry are increasing the productivity of laser material processing using multi-beam processes. The particularity of this project is that all the partial beams can be controlled individually and, therefore, used to produce any type of surface structure. The project partners aim to increase the speed of the process by a factor of twenty to fifty, thus making the whole process significantly more cost effective.

CAPS: Scaling in the kW range

Process knowledge is also a critical factor to further develop materials processing with ultrashort laser pulses with or without multi-beam optics. When the power is increased into the kilowatt range, thermal damage to the part may occur. These effects are explored through complex simulations and processes can be adapted accordingly.

Laser systems for such experiments are available in the application laboratory of Fraunhofer ILT in Aachen. They are part of the Fraunhofer Cluster of Excellence Advanced Photon Sources CAPS, where 13 Fraunhofer institutes jointly develop laser beam sources, process technology and applications for USP laser powers up to 20 kW. A second CAPS laboratory is operated at Fraunhofer IOF in Jena.

Fraunhofer know-how at LASER World of PHOTONICS

At the leading photonics fair LASER World of PHOTONICS in Munich, the laser-drilled microplastic filter will be on display, along with other highlights from the Fraunhofer Cluster of Excellence Advanced Photon Sources CAPS. From April 26 to 29, 2022, experts will be available at Fraunhofer stands A6.441 and B4.239 to provide information on ultrashort pulse laser technology, generation of secondary radiation from THz to X-rays and the revolutionary applications of these last. technologies.

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